Patent Publication Number: US-11664211-B2

Title: Light emitting sealed body, light source device, and method for driving light emitting sealed body

Description:
TECHNICAL FIELD 
     One aspect of the present disclosure relates to a light emitting sealed body, a light source device, and a method for driving a light emitting sealed body. 
     BACKGROUND 
     As a related technique, for example, there is a laser excitation light source disclosed in Japanese Unexamined Patent Publication No. 2017-152117. In the laser excitation light source, a plasma generated in light-emitting gas is maintained by being irradiated with laser light, and light from the plasma is output as output light. 
     In the laser excitation light source as described above, when impure gas exists in an internal space, various defects may occur inside a housing depending on driving conditions. In order to extend the life span of the laser excitation light source, suppressing the occurrence of such defects is required. 
     SUMMARY 
     One aspect of the present disclosure is intended to provide a light emitting sealed body and a light source device having an extended life span, and a method for driving such a light emitting sealed body. 
     A light emitting sealed body according to one aspect of the present disclosure includes: a housing containing light-emitting gas in an internal space; a first window portion provided to the housing and on which first light is incident, wherein the first light is laser light for maintaining a plasma generated in the light-emitting gas; a second window portion provided to the housing and from which second light is emitted, wherein the second light is light from the plasma; and a getter portion including a getter material and disposed in an irradiation region of the first light inside the housing. 
     In the light emitting sealed body, the getter portion including the getter material is disposed in the irradiation region of the first light inside the housing. Accordingly, the getter material can be heated and activated by irradiation with the first light, and impure gas existing in the internal space can be adsorbed by the activated getter material. As a result, the occurrence of a defect caused by impure gas can be suppressed. Therefore, according to the light emitting sealed body, the life span can be extended. 
     The getter portion may further include a support member supporting the getter material. In this case, for example, the getter material can be indirectly heated through the support member, and the excessive heating of the getter material can be suppressed. 
     The getter portion may be disposed such that the getter material faces a side opposite the first window portion. In this case, the spattered getter material can be prevented from moving to a first window portion side and from adhering to the first window portion and the like. 
     The getter portion may be disposed such that the support member is irradiated with the first light. In this case, for example, the getter material can be indirectly heated through the support member, and the excessive heating of the getter material can be suppressed. 
     A melting point of the support member may be higher than a melting point of the getter material. In this case, damage to the support member caused by heating through irradiation with the first light can be suppressed. 
     A thermal conductivity of the support member may be higher than a thermal conductivity of the getter material. In this case, the getter portion can be efficiently heated through the support member. 
     The getter portion may be disposed such that the getter material faces an inner surface of the housing, the inner surface facing the first window portion. In this case, the spattered getter material can adhere to the inner surface. The getter material that has adhered to the inner surface can be heated and activated again by the first light. As a result, impure gas can be adsorbed by the getter material that has adhered to the inner surface. 
     The getter portion may be disposed to define a space between the getter portion and an inner surface of the housing. In this case, the spattered getter material can be kept in the space, and the adhesion of the getter material to other members can be suppressed. 
     An exhaust hole for discharging gas from the internal space to an outside may be formed in the housing, and the getter portion may be disposed between a generation position of the second light and the exhaust hole in the internal space. Gas may be generated from the getter material when the light emitting sealed body is manufactured, but according to the light emitting sealed body, the gas can be easily discharged from the exhaust hole to the outside. 
     A distance from the getter material to a generation position of the second light may be longer than a distance from the generation position of the second light to the first window portion. In this case, the excessive heating of the getter material can be suppressed. 
     The getter material may be fixed to an inner surface of the housing. Also, in this case, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body can be extended. 
     An inner surface of the housing may have an inner peripheral surface extending with a straight line parallel to an optical axis of the first light as a center line, and the getter material may be fixed to the inner peripheral surface. In this case, the getter material can be heated using a bottom edge of the first light that is laser light. For this reason, the occurrence of a defect caused by impure gas can be suppressed while suppressing the excessive heating of the getter material. 
     The getter material may be configured as a non-evaporable type or may be configured as an evaporable type. Also, in these cases, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body can be extended. 
     At least one of the first window portion and the second window portion may include a window member made of a material containing diamond. In this case, light in a wide wavelength range including ultraviolet light can pass through the window member. 
     The housing may be made of a metal material. In this case, impure gas is likely to exist in the internal space, but according to the light emitting sealed body, also in such a case, the occurrence of a defect caused by impure gas can be suppressed. 
     The light emitting sealed body of the present invention may further include a first electrode and a second electrode facing each other with a generation position of the second light interposed between the first electrode and the second electrode. In this case, a plasma can be more reliably generated. 
     A charging pressure of the light-emitting gas in the housing may be 3 MPa or more. In this case, the intensity of the second light emitted from the second window portion can be increased, whereas impure gas is likely to exist inside the housing; however, according to the light emitting sealed body, also in such a case, the occurrence of a defect caused by impure gas can be suppressed. 
     A light source device according to one aspect of the present disclosure includes: the light emitting sealed body; and a light introduction unit that causes the first light to be incident on the first window portion. According to the light source device, the life span can be extended for the above-described reasons. 
     According to one aspect of the present disclosure, there is provided a method for driving a light emitting sealed body including a housing containing light-emitting gas in an internal space, on which first light that is laser light for maintaining a plasma generated in the light-emitting gas is incident and from which second light that is light from the plasma is emitted, and a getter portion including a getter material and being disposed in an irradiation region of the first light inside the housing, the method including: activating the getter material by irradiating the getter material with the first light; and generating the plasma in the light-emitting gas and emitting the second light. In this driving method, the getter material can be heated and activated by irradiation with the first light, and impure gas existing in the internal space can be adsorbed by the activated getter material. As a result, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body can be extended. 
     According to one aspect of the present disclosure, it is possible to provide the light emitting sealed body and the light source device having an extended life span, and the method for driving such a light emitting sealed body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a light emitting sealed body according to a first embodiment. 
         FIG.  2    is a cross-sectional view taken along line II-II of  FIG.  1   . 
         FIG.  3    is a cross-sectional view taken along line III-III of  FIG.  1   . 
         FIG.  4    is an enlarged view of a second window member and a second frame member. 
         FIG.  5    is a cross-sectional view showing a configuration of a protective layer. 
         FIG.  6 A  is a photograph showing a first sample immediately after operation start, and  FIG.  6 B  is a photograph showing the first sample after an elapse of 327 hours. 
         FIGS.  7 A and  7 B  are photographs showing a second sample immediately after operation start. 
         FIGS.  8 A and  8 B  are photographs showing the second sample after an elapse of 168 hours. 
         FIGS.  9 A and  9 B  are photographs showing the second sample after an elapse of 500 hours. 
         FIGS.  10 A and  10 B  are photographs showing the second sample after an elapse of 1051 hours. 
         FIG.  11 A  is a photograph showing the second sample immediately after operation start, and  FIG.  11 B  is a photograph showing the second sample after an elapse of 670 hours. 
         FIG.  12 A  is a cross-sectional view showing an example of a protective layer formed of one ALD layer, and  FIG.  12 B  is a cross-sectional view showing an example of a protective layer formed of first ALD layers and second ALD layers. 
         FIGS.  13 A and  13 B  are photographs showing a third sample immediately after operation start. 
         FIGS.  14 A and  14 B  are photographs showing the third sample after an elapse of 168 hours. 
         FIGS.  15 A and  15 B  are photographs showing the third sample after an elapse of 500 hours. 
         FIGS.  16 A and  16 B  are photographs showing the third sample after an elapse of 1000 hours. 
         FIG.  17    is an enlarged view of the vicinity of a first window member. 
         FIGS.  18 A and  18 B  are photographs showing an example in which foreign matter is generated on the window member. 
         FIGS.  19 A and  19 B  are photographs showing another example in which foreign matter is generated on the window member,  FIG.  19 A  shows a state immediately after operation start, and  FIG.  19 B  shows a state after an elapse of 46 hours. 
         FIG.  20 A  is a photograph showing a fourth sample immediately after operation start,  FIG.  20 B  is a photograph showing the fourth sample after an elapse of 147 hours, and  FIG.  20 C  is a photograph showing the fourth sample after an elapse of 712 hours. 
         FIG.  21 A  is a photograph showing a fifth sample immediately after operation start,  FIG.  21 B  is a photograph showing the fifth sample after an elapse of 147 hours, and  FIG.  21 C  is a photograph showing the fifth sample after an elapse of 712 hours. 
         FIG.  22 A  is a photograph showing a sixth sample immediately after operation start, and  FIG.  22 B  is a photograph showing the sixth sample after an elapse of 168 hours. 
         FIG.  23 A  is a photograph showing the sixth sample after an elapse of 504 hours, and  FIG.  23 B  is a photograph showing the sixth sample after an elapse of 1051 hours. 
         FIG.  24 A  is a photograph showing a seventh sample immediately after operation start, and  FIG.  24 B  is a photograph showing the seventh sample after an elapse of 168 hours. 
         FIG.  25 A  is a photograph showing the seventh sample after an elapse of 504 hours, and  FIG.  25 B  is a photograph showing the seventh sample after an elapse of 1051 hours. 
         FIG.  26 A  is a photograph showing an eighth sample immediately after operation start, and  FIG.  26 B  is a photograph showing the eighth sample after an elapse of 168 hours. 
         FIG.  27 A  is a photograph showing the eighth sample after an elapse of 504 hours, and  FIG.  27 B  is a photograph showing the eighth sample after an elapse of 1051 hours. 
         FIG.  28    is a cross-sectional view of the vicinity of a second end portion of a charging pipe. 
         FIG.  29    is a cross-sectional view of a light emitting sealed body according to a second embodiment. 
         FIG.  30    is a plan view of a getter portion. 
         FIG.  31 A  is a front view of the getter portion, and  FIG.  31 B  is a side view of the getter portion. 
         FIG.  32    is another cross-sectional view of the light emitting sealed body according to the second embodiment. 
         FIGS.  33 A and  33 B  are photographs showing an example in which foreign matter is generated on electrodes. 
         FIG.  34 A  is a photograph showing a ninth sample immediately after operation start,  FIG.  34 B  is a photograph showing the ninth sample after an elapse of 260 hours, and  FIG.  34 C  is a photograph showing the ninth sample after an elapse of 670 hours. 
         FIGS.  35 A,  35 B, and  35 C  are photographs showing a tenth sample immediately before operation start. 
         FIGS.  36 A,  36 B, and  36 C  are photographs showing the tenth sample immediately after operation start. 
         FIGS.  37 A,  37 B, and  37 C  are photographs showing the tenth sample after an elapse of 165 hours. 
         FIGS.  38 A and  38 B  are photographs showing an eleventh sample immediately before operation start. 
         FIGS.  39 A and  39 B  are photographs showing the eleventh sample immediately after operation start. 
         FIGS.  40 A and  40 B  are photographs showing the eleventh sample after an elapse of 165 hours. 
         FIGS.  41 A and  41 B  are photographs showing a twelfth sample immediately before operation start. 
         FIGS.  42 A and  42 B  are photographs showing the twelfth sample immediately after operation start. 
         FIGS.  43 A and  43 B  are photographs showing the twelfth sample after an elapse of 165 hours. 
         FIG.  44 A  is a photograph showing a thirteenth sample immediately after operation start, and  FIG.  44 B  is a photograph showing the thirteenth sample after an elapse of 262 hours. 
         FIG.  45    is a cross-sectional view of a light emitting sealed body according to a fifth modification example. 
         FIG.  46    is a cross-sectional view of a light emitting sealed body according to a sixth modification example. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, the same reference signs are used for the same or equivalent elements, and a description thereof will not be repeated. 
     First Embodiment 
     [Laser Excitation Light Source] 
     As shown in  FIGS.  1  to  3   , a light emitting sealed body  1  includes a housing  10 . The housing  10  is charged with light-emitting gas GS. The light-emitting gas GS is, for example, xenon and is discharge gas in this example. For example, the light emitting sealed body  1  forms a laser excitation light source (light source device), together with a laser light source that outputs first light L 1  that is laser light. In the laser excitation light source, a plasma is generated in the light-emitting gas GS. The first light L 1  that is laser light for maintaining the plasma is incident on the light emitting sealed body  1 , and second light L 2  that is light from the plasma is emitted from the light emitting sealed body  1  as output light. The first light is, for example, light in a near-infrared region and has a wavelength of approximately 800 nm to 1100 nm. The second light L 2  is, for example, light in an ultraviolet region to a mid-infrared region and has, for example, a wavelength of approximately 220 nm to 20 μm. 
     The laser excitation light source further includes, for example, a mirror, an optical system, and the like in addition to the light emitting sealed body  1  and the above-described laser light source, and these elements are configured to be contained in a case. The laser light source is, for example, a laser diode. The mirror reflects the first light L 1  from the laser light source toward the optical system. The optical system includes one or a plurality of lenses. The optical system guides the first light L 1  to the light emitting sealed body  1  while condensing the first light L 1 . The laser light source, the mirror, and the optical system form a light introduction unit that causes the first light L 1  to be incident on the housing  10  from a first window portion  20  to be described later. Alternatively, the laser excitation light source itself may not include the laser light source. For example, the laser excitation light source may include an optical fiber that guides light from a laser light source disposed outside to the mirror, instead of its own laser light source. In this case, the optical fiber, the mirror, and the optical system form a light introduction unit that causes the first light L 1  to be incident on the housing  10  from the first window portion  20 . 
     [Light Emitting Sealed Body] 
     The light emitting sealed body  1  further includes the first window portion  20 , two second window portions  30 , a first electrode  40 , a second electrode  50  in addition to the housing  10 . 
     The housing  10  includes a housing body  11 . The housing body  11  is formed from a metal material in a substantially box shape and contains the light-emitting gas GS. More specifically, an internal space S 1  that is sealed is formed inside the housing body  11 , and the internal space S 1  is filled with the light-emitting gas GS. An example of the metal material forming the housing body  11  is stainless steel. In this case, the housing body  11  has a light-shielding property with respect to the first light L 1  and to the second light L 2 . Namely, the housing body  11  is made of a light-shielding material that does not transmit the first light L 1  and the second light L 2 . 
     A first opening  12  and two second openings  13  are formed in the housing body  11 . The first light L 1  is incident on the first opening  12  along a first optical axis A 1 . The first opening  12  is formed in, for example, a circular shape when viewed in a direction parallel to the first optical axis A 1  (hereinafter, also referred to as a Z direction). In this example, the first optical axis A 1  passes through a center of the first opening  12  when viewed in the Z direction. The first opening  12  includes an inner portion  12   a , an intermediate portion  12   b , and an outer portion  12   c . The inner portion  12   a  is open to the internal space S 1 . The outer portion  12   c  is open to an outside of the housing body  11 . The intermediate portion  12   b  is connected to the inner portion  12   a  and to the outer portion  12   c . Each of the inner portion  12   a , the intermediate portion  12   b , and the outer portion  12   c  has, for example, a cylindrical shape. When viewed in an axial direction, an outer shape of the intermediate portion  12   b  is larger than an outer shape of the inner portion  12   a , and an outer shape of the outer portion  12   c  is larger than the outer shape of the intermediate portion  12   b . An “outer shape” of an element when viewed in an axial direction means a diameter when the element has a circular shape, and means a maximum length when the element has a non-circular shape. 
     The second light L 2  is emitted from each of the second openings  13  along a second optical axis A 2 . Each of the second openings  13  is formed in, for example, a circular shape when viewed in a direction parallel to the second optical axis A 2  (hereinafter, also referred to as a Y direction). In this example, the second optical axis A 2  passes through a center of each of the second openings  13  when viewed in the Y direction. Each of the second openings  13  includes an inner portion  13   a , an intermediate portion  13   b , and an outer portion  13   c . The inner portion  13   a  is open to the internal space S 1 . The outer portion  13   c  is open to the outside of the housing body  11 . The intermediate portion  13   b  is connected to the inner portion  13   a  and to the outer portion  13   c . Each of the inner portion  13   a , the intermediate portion  13   b , and the outer portion  13   c  has, for example, a cylindrical shape. When viewed in an axial direction, an outer shape of the intermediate portion  13   b  is larger than an outer shape of the inner portion  13   a , and an outer shape of the outer portion  13   c  is larger than the outer shape of the intermediate portion  13   b.    
     The first optical axis A 1  intersects the second optical axis A 2  in the internal space S 1 . Namely, the first opening  12  and the second openings  13  are disposed such that the first optical axis A 1  and the second optical axis A 2  intersect each other. An intersection point C of the first optical axis A 1  and the second optical axis A 2  is located in the internal space S 1 . In this example, the first optical axis A 1  perpendicularly intersects the second optical axis A 2 , but the first optical axis A 1  may intersect the second optical axis A 2  at an angle other than the right angle. The first optical axis A 1  is not parallel to the second optical axis A 2 . The first optical axis A 1  does not pass through the second openings  13 , and the second optical axis A 2  does not pass through the first opening  12 . 
     The first window portion  20  airtightly seals the first opening  12 . The first window portion  20  includes a first window member  21 . The first window member  21  is formed in, for example, a circular flat plate shape from a light transmissive material that transmits the first light L 1 . In this example, the first window member  21  is made of sapphire and transmits light having a wavelength of 5 μm or less. The first window member  21  transmits the first light L 1  at the first opening  12 . 
     The first window member  21  is fixed to a first frame member  61  and is fixed to the housing body  11  via the first frame member  61 . Hereinafter, the first frame member  61  will be described as being regarded as a part of the housing  10 . In this case, the housing  10  includes the first frame member  61  in addition to the housing body  11  described above. However, the first frame member  61  can also be regarded as a part of the first window portion  20 . In this case, the housing  10  is formed of only the housing body  11 . 
     The first frame member  61  is formed in, for example, a frame shape from a metal material such as Kovar metal. The first frame member  61  is formed in a substantially cylindrical shape as a whole. The first frame member  61  includes a first portion  62  having a cylindrical shape and a second portion  63  having a cylindrical shape that is integrally formed with the first portion  62 . An outer shape of the second portion  63  is larger than an outer shape of the first portion  62 . The first window member  21  is disposed inside the first portion  62  and is fixed to the first frame member  61 . Details of a mode for fixing the first window member  21  to the first frame member  61  will be described later. 
     A flange portion  63   a  having a circular ring shape and protruding outward in a radial direction is formed on an outer surface of the second portion  63 . The first frame member  61  is fixed to the housing body  11  in a state where the flange portion  63   a  is disposed inside the intermediate portion  12   b  of the first opening  12 . In this state, a part of the first portion  62  of the first frame member  61  protrudes from the first opening  12 . The first window member  21  is disposed to face the intersection point C of the first optical axis A 1  and the second optical axis A 2 . The first frame member  61  is airtightly fixed to the housing body  11  at the flange portion  63   a , for example, by laser welding. 
     Each of the second window portions  30  airtightly seals the second opening  13 . Each of the second window portions  30  includes a second window member  31 . The second window member  31  is formed in, for example, a circular flat plate shape from a light transmissive material that transmits the second light L 2 . In this example, the second window member  31  is made of diamond and transmits light having a wavelength of 20 μm or less. The second window member  31  transmits the second light L 2  at the second opening  13 . 
     The second window member  31  is fixed to a second frame member  71  and is fixed to the housing body  11  via the second frame member  71 . Hereinafter, the second frame member  71  will be described as being regarded as a part of the housing  10 . In this case, the housing  10  includes the second frame members  71  in addition to the housing body  11  and the first frame member  61  described above. However, the second frame member  71  can also be regarded as a part of the second window portion  30 . In this case, the housing  10  is formed of only the housing body  11 . 
     The second frame member  71  is formed in, for example, a frame shape from a metal material such as Kovar metal. The second frame member  71  is formed in a substantially cylindrical shape as a whole. The second frame member  71  includes a first portion  72  having a cylindrical shape and a second portion  73  having a cylindrical shape and integrally formed with the first portion  72 . An outer shape of the second portion  73  is larger than an outer shape of the first portion  72 . The second window member  31  is disposed inside the first portion  72  and is fixed to the second frame member  71 . Details of a mode for fixing the second window member  31  to the second frame member  71  will be described later. 
     A flange portion  73   a  having a circular ring shape and protruding outward in the radial direction is formed on an outer surface of the second portion  73 . The second frame member  71  is fixed to the housing  10  in a state where the flange portion  73   a  is disposed inside the intermediate portion  13   b  of the second opening  13 . In this state, a part of the first portion  72  of the second frame member  71  protrudes from the second opening  13 . The second window member  31  is disposed to face the intersection point C of the first optical axis A 1  and the second optical axis A 2 . The second frame member  71  is airtightly fixed to the housing body  11  at the flange portion  73   a , for example, by laser welding. 
     The first electrode  40  extends along an X direction perpendicular to both the Y direction and the Z direction. The first electrode  40  faces the second electrode  50  with the intersection point C of the first optical axis A 1  and the second optical axis A 2  interposed therebetween. In the X direction, a distance between the intersection point C and a tip of the first electrode  40  is equal to a distance between the intersection point C and a tip of the second electrode  50 . The first electrode  40  is made of, for example, a metal material such as tungsten. The first electrode  40  is formed in a substantially rod shape as a whole. The first electrode  40  includes a first support portion  41  on a base end side and a first discharge portion  42  located on a tip side to be closer to the second electrode  50  than the first support portion  41 . The first electrode  40  is fixed to the housing body  11  at the first support portion  41  via an insulating member  3  and is electrically separated from the housing  10 . The first discharge portion  42  has a smaller diameter than that of the first support portion  41  and has a pointed shape. The first discharge portion  42  is disposed inside the housing  10  (in the internal space S 1 ). 
     The insulating member  3  includes a body portion  3   a  and a tubular portion  3   b . The insulating member  3  is made of, for example, an insulating material such as alumina (aluminum oxide) or ceramic. The body portion  3   a  is formed in, for example, a columnar shape and holds the first support portion  41  of the first electrode  40 . The tubular portion  3   b  is formed in a cylindrical shape to extend from the body portion  3   a  along the X direction and surrounds a part on a first support portion  41  side (base end side) of the first discharge portion  42 . A third opening  14  is formed in the housing body  11 , and the tubular portion  3   b  is disposed inside the third opening  14 . The insulating member  3  is airtightly fixed to the housing body  11  via a connection member  4  made of metal. 
     The second electrode  50  extends along the X direction. The second electrode  50  faces the first electrode  40  with the intersection point C of the first optical axis A 1  and the second optical axis A 2  interposed therebetween. The second electrode  50  is made of, for example, a metal material such as tungsten. The second electrode  50  is formed in a substantially rod shape having a larger diameter than that of the first electrode  40 , as a whole. The second electrode  50  includes a second support portion  51  on a base end side and a second discharge portion  52  located on a tip side to be closer to the first electrode  40  than the second support portion  51 . The second electrode  50  is fixed to the housing body  11  at the second support portion  51  and is electrically connected to the housing  10 . More specifically, a fourth opening  15  is formed in the housing body  11 , and the second support portion  51  is disposed inside the fourth opening  15 . The second discharge portion  52  has a smaller diameter than that of the second support portion  51  and has a pointed shape. The second discharge portion  52  is disposed inside the housing  10  (in the internal space S 1 ). 
     A charging hole  16  is formed in the housing body  11 . The charging hole  16  is used to charge the internal space S 1  with the light-emitting gas GS when the light emitting sealed body  1  is manufactured. In addition, the charging hole  16  also functions as an exhaust hole that discharges gas (impure gas such as residual air or gas released from forming materials) from the internal space S 1  to the outside when the light emitting sealed body  1  is manufactured. A charging pipe  17  is connected to the charging hole  16 . The charging pipe  17  is formed in, for example, a cylindrical shape from a metal material such as copper and includes a first end portion  17   a  and a second end portion  17   b . The first end portion  17   a  is disposed inside the charging hole  16 , and the charging pipe  17  is connected to the internal space S 1  at the first end portion  17   a . The second end portion  17   b  is sealed by being crushed. Details of the sealed portion will be described later. 
     In the light emitting sealed body  1 , the internal space S 1  is defined by the housing  10 , the first window portion  20 , and the second window portions  30 . In the light emitting sealed body  1 , the internal space S 1  is also defined by the first electrode  40 , the second electrode  50 , the insulating member  3 , the connection member  4 , and the charging pipe  17 . The entirety of the internal space S 1  is filled with the light-emitting gas GS. Namely, the internal space S 1  is charged with the light-emitting gas GS. A charging pressure (maximum charging pressure) of the light-emitting gas GS is, for example, 3 MPa (30 atm) or more, but may be 5 MPa (50 atm) or more. The light emitting sealed body  1  can withstand an internal pressure of 16 MPa or more. 
     [Operation Example] 
     In the laser excitation light source, a voltage application circuit disposed inside the case applies a negative voltage pulse to the first electrode  40  with the second electrode  50  set to a ground potential. Accordingly, electrons are released from the first electrode  40  toward the second electrode  50 . As a result, an arc discharge is generated and a plasma is generated between the first electrode  40  and the second electrode  50  (at intersection point C). The plasma is irradiated with the first light L 1  from the laser light source (light introduction unit) through the first window member  21 . Accordingly, the generated plasma is maintained. The second light L 2  that is light from the plasma is emitted to the outside through the second window member  31 , as output light. In the laser excitation light source, the second light L 2  is emitted from two second window members  31  toward both sides in the Y direction. Incidentally, a positive voltage pulse may be applied to the first electrode  40  as a trigger voltage for generating a plasma. In this case, electrons are released from the second electrode  50  toward the first electrode  40 . 
     [Fixing Condition of Second Window Member] 
     As shown in  FIG.  4   , the second window member  31  of the second window portion  30  is formed in a circular flat plate shape and has a first major surface  31   a , a second major surface  31   b , and a side surface  31   c . The first major surface  31   a  is a light incident surface on which the second light L 2  is incident, and is a surface on an internal space S 1  side (upper side in  FIG.  4   ). The second major surface  31   b  is a surface opposite the first major surface  31   a  and is a light-emitting surface that emits the second light L 2 . In this example, the first major surface  31   a  and the second major surface  31   b  are flat surface perpendicular to the Y direction, and the side surface  31   c  is a cylindrical surface connected to the first major surface  31   a  and to the second major surface  31   b.    
     The second window member  31  is disposed inside the first portion  72  of the second frame member  71 . Specifically, a space inside the second frame member  71  includes a disposition portion  74  formed inside the first portion  72 , an intermediate portion  75  formed from the inside of the first portion  72  to the inside of the second portion  73 , and an outer portion  76  formed inside the second portion  73 . The intermediate portion  75  has a truncated cone shape in which the outer shape increases toward the outside (side opposite the internal space  51 ) (lower side in  FIG.  4   ) in the Y direction. The outer portion  76  is formed in a cylindrical shape having a larger outer shape than that of the intermediate portion  75 . 
     The disposition portion  74  includes a large-diameter portion  74   a  having a cylindrical shape and a small-diameter portion  74   b  having a cylindrical shape that is disposed between the large-diameter portion  74   a  and the intermediate portion  75 . An outer shape of the large-diameter portion  74   a  is larger than an outer shape of the small-diameter portion  74   b . The second window member  31  is disposed over the large-diameter portion  74   a  and the small-diameter portion  74   b . A part of the second major surface  31   b  of the second window member  31  is in contact with a bottom surface  74   b   1  of the small-diameter portion  74   b , and a part of the side surface  31   c  of the second window member  31  is in contact with an inner surface  74   b   2  of the small-diameter portion  74   b.    
     The second window member  31  is fixed to the second frame member  71  by a joining material  35 . Specifically, the joining material  35  joins the side surface  31   c  of the second window member  31  and the first portion  72  of the second frame member  71  to each other over an entire circumference. In this example, the joining material  35  is disposed in the large-diameter portion  74   a  and is in contact with the side surface  31   c  and with a bottom surface  74   a   1  and an inner surface  74   a   2  of the large-diameter portion  74   a . The joining material  35  is, for example, a metal brazing material and, more specifically, is titanium-doped silver brazing. The titanium-doped silver brazing is, for example, a brazing material composed of 70% silver, 28% copper, and 2% Ti, and is, for example, TB-608T of Tokyo Braze Co., Ltd. 
     A protective layer  80  is formed on the first major surface  31   a  of the second window member  31 . In this example, the protective layer  80  is integrally formed to cover the entirety of surfaces of the second window member  31 , the second frame member  71 , and the joining material  35 , the surfaces being exposed to the outside. In  FIG.  4   , a region where the protective layer  80  is formed is shown by an alternate long and two short dashed line. Namely, the protective layer  80  is formed to reach the second frame member  71  from the second window member  31 , and covers the joining material  35 . The protective layer  80  is formed to cover the entirety of the surface of the second frame member  71  except for a contact portion between the second window member  31  and the joining material  35 . 
     As shown in  FIG.  5   , the protective layer  80  includes a plurality (two in this example) of first layers  81  and a plurality (two in this example) of second layers  82 . The plurality of first layers  81  and the plurality of second layers  82  are alternately stacked on the first major surface  31   a  of the second window member  31 . In this example, one of the first layers  81  is in contact with the first major surface  31   a , and one of the second layers  82  is exposed to the outside. 
     The protective layer  80  is made of an inorganic material and transmits at least some of the second light L 2 . As one example, each of the first layers  81  are an ALD layer (first ALD layer) made of Al 2 O 3  (first material), and each of the second layers  82  is an ALD layers (second ALD layer) made of TiO 2  (second material). The ALD layer is a layer formed by atomic layer deposition (ALD). A transmittance of Al 2 O 3  to ultraviolet light is higher than a transmittance of diamond to ultraviolet light. A transmittance of TiO 2  to ultraviolet light is lower than the transmittance of diamond to ultraviolet light. For this reason, in this example, the majority of ultraviolet light included in the second light L 2  is absorbed by the second layers  82 . The protective layer  80  has, for example, a thickness of approximately 0.1 μm. 
     The suppression of the occurrence of an opacity phenomenon by the protective layer  80  will be described with reference to  FIGS.  6 A to  10 B . In a case where the window member is made of diamond, when the laser excitation light source is continuously driven, a phenomenon in which the window member becomes opaque (opacity phenomenon) can occur depending on driving conditions. 
       FIG.  6 A  is a photograph showing a first sample immediately after operation start, and  FIG.  6 B  is a photograph showing the first sample after an elapse of 327 hours. The first sample corresponds to a configuration in which the protective layer  80  is not formed in the light emitting sealed body  1 . The focal point is on the second window member  31  in photographs on left sides of  FIGS.  6 A and  6 B , and the focal point is on the first electrode  40  and on the second electrode  50  in photographs on right sides of  FIGS.  6 A and  6 B . In  FIGS.  6 A and  6 B , images of the first electrode  40  and the second electrode  50  are captured through the second window member  31 . This point is also the same for  FIGS.  7 B,  8 B,  9 B , and  10 B, and photographs on right sides of  FIGS.  11 A, and  11 B  and for  FIGS.  13 B,  14 B,  15 B, and  16 B  which will be described later. 
     As shown in  FIGS.  6 A and  6 B , the first electrode  40  and the second electrode  50  were visually recognized through the second window member  31  immediately after operation start, but after an elapse of 327 hours, the transmittance of the second window member  31  to visible light decreased, and the first electrode  40  and the second electrode  50  could not be visually recognized through the second window member  31 . After an elapse of 327 hours, the color of the second window member  31  was changed to white, and the second window member  31  became opaque. 
     It is considered that such an opacity phenomenon can occur due to at least one of the following factors. First, it is considered that the second window member  31  is scraped into a crater shape by impure gas (gas other than the light-emitting gas GS, for example, oxygen and the like) existing in the internal space S 1  inside the housing  10 . It is considered that another factor is the influence of ultraviolet light included in the second light L 2  that is light from the plasma. It is considered that further another factor is an increase in the temperature of the light emitting sealed body  1  during driving. During driving, the temperature of the light emitting sealed body  1  rises due to irradiation with laser light and radiant heat from the plasma. 
       FIGS.  7 A to  10 B  are photographs showing a second sample immediately after operation start, after an elapse of 168 hours, after an elapse of 500 hours, and after an elapse of 1051 hours, respectively. The second sample corresponds to the light emitting sealed body  1 . The focal point is on the second window member  31  in  FIG.  7 A , and the focal point is on the first electrode  40  and on the second electrode  50  in  FIG.  7 B . This point is also the same for  FIGS.  8 A to  10 B .  FIG.  11 A  is a photograph showing the second sample immediately after operation start, and  FIG.  11 B  is a photograph showing the second sample after an elapse of 670 hours. The focal point is on the second window member  31  in photographs on left sides of  FIGS.  11 A and  11 B , and the focal point is on the first electrode  40  and on the second electrode  50  in photographs on right sides of  FIGS.  11 A and  11 B . 
     As shown in  FIGS.  7 A to  11 B , in the second sample, the opacity phenomenon did not occur even after an elapse of 1051 hours from the start of driving. From these results, it can be seen that the occurrence of the opacity phenomenon can be suppressed by forming the protective layer  80 . 
     As described above, in the light emitting sealed body  1 , the second window member  31  of the second window portion  30  that emits the second light L 2  is made of a material containing diamond. In this case, there is a possibility of the occurrence of a phenomenon in which the second window member  31  described above becomes opaque (opacity phenomenon). In this respect, in the light emitting sealed body  1 , the protective layer  80  that is made of an inorganic material and transmits at least some of the second light L 2  is formed on the first major surface  31   a  (surface on the internal space S 1  side) of the second window member  31 . Accordingly, for example, the contact of impure gas existing in the internal space S 1  inside the housing  10  with the second window member  31  can be suppressed. As a result, the occurrence of the opacity phenomenon can be suppressed, and the life span of the light emitting sealed body  1  can be extended. 
     The protective layer  80  includes the plurality of layers. Accordingly, the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The protective layer  80  contains a material (TiO 2 ) having a lower transmittance to ultraviolet light than diamond. Accordingly, the second window member  31  can be prevented from being affected by ultraviolet light and from becoming opaque, and the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The protective layer  80  includes ALD layers. Accordingly, since the ALD layers are uniform and dense layers, the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The protective layer  80  includes the first ALD layers made of the first material (first layers  81 ) and the second ALD layers made of the second material different from the first material (second layers  82 ). Accordingly, since the protective layer  80  includes the plurality of layers, the occurrence of the opacity phenomenon can be more reliably suppressed. In addition, the occurrence of the opacity phenomenon can be more reliably suppressed also due to the fact that the ALD layers are uniform and dense layers. In addition, holes can be formed in the ALD layer with a certain probability during the formation of the layer, but since the first ALD layers and the second ALD layers made of different materials are included, the positions of holes between the first ALD layers and the second ALD layers can be different from each other. As a result, the occurrence of a situation where impure gas existing in the internal space S 1  inside the housing  10  comes into contact with the second window member  31  through the holes can be suppressed. 
     This point will be further described with reference to  FIGS.  12 A and  12 B .  FIG.  12 A  is a cross-sectional view showing an example (first modification example) of the protective layer  80  formed of only one ALD layer  83 . The ALD layer  83  is made of, for example, Al 2 O 3 . Also, in the first modification example, similarly to the first embodiment, the occurrence of the opacity phenomenon can be suppressed, and the life span of the light emitting sealed body  1  can be extended. In addition, since the transmittance of Al 2 O 3  to ultraviolet light is higher than that of diamond, the second light L 2  including ultraviolet light can be emitted from the second window portion  30 . In addition, the layer made of Al 2 O 3  can be stably formed on the second window member  31  made of diamond. 
     On the other hand, as shown in  FIG.  12 A , holes (pinholes) HL can be formed in the ALD layer  83  with a certain probability during the formation of the layer. In this case, impure gas GR existing in the internal space S 1  inside the housing  10  comes into contact with the second window member  31  through the holes HL, which is a concern. In contrast, in the light emitting sealed body  1  of the first embodiment, the protective layer  80  includes two ALD layers (the first layer  81  and the second layer  82 ) made of different materials. Accordingly, as shown in  FIG.  12 B , the position of a hole HL 1  formed in the first layer  81  and the position of a hole HL 2  formed in the second layer  82  can be different from each other. As a result, the impure gas GR is unlikely to reach the second window member  31  through the holes HL 1  and HL 2 , and the occurrence of a situation where the impure gas GR comes into contact with the second window member  31  can be suppressed. 
     The protective layer  80  includes, for example, the layer made of TiO 2  (second layer  82 ). Accordingly, since the transmittance of TiO 2  to ultraviolet light is lower than that of diamond, the second window member  31  can be prevented from being affected by ultraviolet light and from becoming opaque, and the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The protective layer  80  includes the first layers  81  made of Al 2 O 3  and the second layers  82  made of TiO 2 . Accordingly, since the protective layer  80  includes the plurality of layers, the occurrence of the opacity phenomenon can be more reliably suppressed. In addition, the second window member  31  can be prevented from being affected by ultraviolet light and from becoming opaque, and the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The housing  10  is made of a metal material. In this case, the charging pressure of the light-emitting gas GS can be increased, and the intensity of the second light L 2  emitted from the second window portion  30  can be increased. In addition, in this case, impure gas is likely to exist in the internal space S 1 , and the opacity phenomenon is likely to occur. Namely, the housing  10  is charged with the light-emitting gas GS in a high vacuum state by vacuum baking, but when the temperature rises or the housing  10  is irradiated with light during driving, impure gas may be released from the housing  10 . For example, impure gas adsorbed in irregularities existing on a surface of the housing  10  can be released during driving. When the housing  10  is formed by cutting, large irregularities are likely to be formed. In addition, impure gas adsorbed in the housing  10  can also be released. In this respect, according to the light emitting sealed body  1 , even when impure gas is likely to exist in the internal space S 1 , the occurrence of the opacity phenomenon can be suppressed. 
     The protective layer  80  is formed to reach the second frame member  71  from the second window member  31 . Accordingly, the release of impure gas from the second frame member  71  can be suppressed, and the occurrence of the opacity phenomenon can be more reliably suppressed. 
     The protective layer  80  covers the joining material  35  that joins the second window member  31  and the second frame member  71 . Accordingly, the release of foreign matter from the joining material  35  can be suppressed. 
     The charging pressure of the light-emitting gas GS in the housing  10  is 3 MPa or more. In this case, the brightness of the plasma generated in the light-emitting gas GS can be increased, so that the intensity of the second light L 2  emitted from the second window portion  30  can be increased. For example, when the charging pressure is 3 MPa, the intensity of the second light L 2  is increased by approximately five times or more as compared to a case where the charging pressure is 1 MPa. When the charging pressure is 5 MPa, the intensity of the second light L 2  is increased by approximately eight times as compared to the case where the charging pressure is 1 MPa. On the other hand, the opacity phenomenon is likely to occur due to an increase in the intensity of the second light L 2 . In addition, since the temperature of the light emitting sealed body  1  when driven rises due to an increase in light output, the opacity phenomenon is likely to occur. In addition, when the charging pressure is increased, the opacity phenomenon is likely to occur also due to the fact that impure gas is likely to exist in the internal space S 1 . In this respect, according to the light emitting sealed body  1 , also in such a case, the occurrence of the opacity phenomenon can be suppressed. 
     As a second modification example, the second layer  82  in the first embodiment may be an ALD layer made of SiO 2  (second material) (second ALD layer). A transmittance of SiO 2  to ultraviolet light is higher than the transmittance of diamond to ultraviolet light and is lower than the transmittance of Al 2 O 3  to ultraviolet light. Also, in the second modification example, similarly to the first embodiment, the occurrence of the opacity phenomenon can be suppressed, and the life span of the light emitting sealed body  1  can be extended. 
     This point will be described with reference to  FIGS.  13 A and  16 B .  FIGS.  13 A to  16 B  are photographs showing a third sample immediately after operation start, after an elapse of 168 hours, after an elapse of 500 hours, and after an elapse of 1000 hours, respectively. The third sample corresponds to the second modification example. The focal point is on the second window member  31  in  FIG.  13 A , and the first electrode  40  and the focal point is on the second electrode  50  in  FIG.  13 B . This point is also the same for  FIGS.  14 A to  16 B . As shown in  FIGS.  13 A to  16 B , in the third sample, the opacity phenomenon did not occur even after an elapse of 1000 hours from the start of driving. 
     In addition, in the second modification example, the protective layer  80  is made of only a material having a higher transmittance to ultraviolet light than diamond. Accordingly, the second light L 2  including ultraviolet light can be emitted from the second window portion  30 . 
     In the first embodiment, the protective layer  80  may cover at least a part of the first major surface  31   a  of the second window member  31  and, for example, may be formed only on the first major surface  31   a . Alternatively, the protective layer  80  may be formed to cover only surfaces of the second window member  31 , the second frame member  71 , and the joining material  35 , the surfaces being exposed to the internal space S 1 . The protective layer  80  may be able to transmit at least some of the second light L 2 , and may transmit some of the second light L 2  as in the first embodiment or may transmit all the second light L 2 . In the first embodiment, the protective layer  80  is an ALD layer, but the protective layer  80  may be a layer formed by deposition. For example, the protective layer  80  may be a layer formed by sputtering, chemical vapor deposition (CVD), ion plating, vacuum deposition, resistive thermal deposition, or the like. When the protective layer  80  is formed by deposition, the protective layer  80  can be formed at any position (region). In the first embodiment, the second window member  31  of the second window portion  30  is made of a material containing diamond, and the protective layer  80  made of an inorganic material is formed on the first major surface  31   a  (surface on the internal space S 1  side) of the second window member  31 , but instead of or in addition to this configuration, the first window member  21  of the first window portion  20  may be made of a material containing diamond, and the protective layer  80  made of an inorganic material may be formed at least on a surface on the internal space S 1  side (second major surface  21   b  to be described later) of the first window member  21 . In this case, the occurrence of the opacity phenomenon on the first window member  21  can be suppressed, and the life span of the light emitting sealed body  1  can be further extended. 
     [Fixing Condition of First Window Member] 
     As shown in  FIG.  17   , the first window member  21  of the first window portion  20  is formed in a circular flat plate shape and has a first major surface  21   a , the second major surface  21   b , and a side surface  21   c . The first major surface  21   a  is a light incident surface on which the first light L 1  is incident, and is a surface on a side opposite the internal space S 1  (lower side in  FIG.  17   ). The second major surface  21   b  is a surface opposite the first major surface  21   a  and is a light-emitting surface that emits the first light L 1 . In this example, the first major surface  21   a  and the second major surface  21   b  are flat surface perpendicular to the Z direction, and the side surface  21   c  is a cylindrical surface connected to the first major surface  21   a  and to the second major surface  21   b.    
     The first window member  21  is disposed inside the first portion  62  of the first frame member  61 . The first portion  62  includes a wall portion  65  having a cylindrical shape and facing the side surface  21   c  of the first window member  21 . A flange portion  66  having a circular ring shape and protruding inward in the radial direction is formed on an inner surface  65   a  of the wall portion  65 . The first window member  21  is disposed inside the first portion  62  of the first frame member  61  such that the first major surface  21   a  faces a first surface  66   a  of the flange portion  66  and the side surface  21   c  faces the inner surface  65   a  of the wall portion  65 . An end surface  65   b  of the wall portion  65  in the Z direction (direction perpendicular to the first major surface  21   a ) is located on the internal space S 1  side (upper side in  FIG.  17   ) with respect to the first window member  21  (second major surface  21   b ). 
     A metallized layer  26  is formed over the entirety of the side surface  21   c  of the first window member  21 . The metallized layer  26  is made of, for example, molybdenum-manganese (Mo—Mn) and has a thickness of approximately several hundreds of μm. A plating layer  27  is formed on the metallized layer  26 . The plating layer  27  is made of, for example, nickel and has a thickness of approximately several μm. The plating layer  27  covers an entire surface of the metallized layer  26  except for a contact portion between the metallized layer  26  and the first window member  21  such that the metallized layer  26  is not exposed. The plating layer  27  functions as an antioxidant layer that prevents the oxidation of the metallized layer  26 . 
     The first window member  21  is joined to the first frame member  61  by a joining material  25 . Specifically, the joining material  25  is joined to the plating layer  27 , so that the first window member  21  is joined to the first frame member  61 . The joining material  25  joins the side surface  21   c  of the first window member  21  and the wall portion  65  of the first frame member  61  to each other over an entire circumference. 
     The joining material  25  is inserted between the first major surface  21   a  of the first window member  21  and the first surface  66   a  of the flange portion  66  of the first frame member  61 . The joining material  25  is not familiar with the first major surface  21   a  and is locally in contact with the first major surface  21   a  but is not joined. Namely, the joining material  25  is inserted between the first major surface  21   a  and the flange portion  66  in a state where the joining material  25  is not bonded to the first major surface  21   a . In this example, the joining material  25  is formed to wrap around the flange portion  66 , and covers a part of a second surface  66   b  of the flange portion  66 . The second surface  66   b  is a surface of the flange portion  66  on the side opposite to the first window member  21 . 
     The joining material  25  covers the metallized layer  26  and the plating layer  27  on the side opposite the internal space S 1  (lower side in  FIG.  17   ) such that the metallized layer  26  and the plating layer  27  are not exposed. Namely, edge portions on an opposite side of the metallized layer  26  and the plating layer  27  from the internal space S 1  are covered with the joining material  25  and are not exposed to the outside. 
     The joining material  25  also covers the metallized layer  26  and the plating layer  27  on the internal space S 1  side (upper side in  FIG.  17   ) such that the metallized layer  26  and the plating layer  27  are not exposed. Namely, edge portions of the metallized layer  26  and the plating layer  27  on the internal space S 1  side are covered with the joining material  25  and are not exposed to an outside (internal space S 1 ). In addition, the joining material  25  is provided to reach the end surface  65   b  of the wall portion  65  in the Z direction and covers the entirety of the end surface  65   b . In this example, the joining material  25  climbs over the end surface  65   b  to reach an outer surface  65   c  of the wall portion  65 , and covers a part of the outer surface  65   c.    
     The joining material  25  is, for example, a metal brazing material and, more specifically, is gold-copper brazing. The joining material  25  has, for example, a thickness of approximately several hundreds of μm. The joining material  25  is formed, for example, by disposing a wire made of a metal brazing material at a boundary portion between the first window member  21  and the first frame member  61  and by melting the wire at approximately 1000° C. through baking. 
     The suppression of the generation of foreign matter on the window member will be described with reference to  FIGS.  18 A to  23 B . For example, in a case where the window member is joined to the housing by a joining material consisting of silver brazing, when the laser excitation light source is continuously driven, foreign matter may be seen on the window member. Since the foreign matter on the window member is dirt on the window member and can interfere with the transmission of laser light or emitted light, suppressing the foreign matter is required. 
       FIGS.  18 A and  18 B  are photographs showing an example in which foreign matter is generated on the first window member  21 .  FIGS.  19 A and  19 B  are photographs showing another example in which foreign matter is generated on the first window member  21 ,  FIG.  19 A  shows a state immediately after operation start, and  FIG.  19 B  shows a state after an elapse of 46 hours. Samples shown in  FIGS.  18 A to  19 B  correspond to a configuration in which silver brazing is used as the joining material  25  in the light emitting sealed body  1 , instead of gold-copper brazing. 
     In  FIGS.  18 A and  18 B , locations where foreign matter is generated are indicated by reference sign P. Foreign matter shown in  FIGS.  18 A and  18 B  is generated after a relatively long time has elapsed after the start of driving. It is considered that when the temperature rises due to driving, the silver brazing contained in the joining material moves to the surface of the first window member  21  to generate the foreign matter (bleed-out phenomenon). It is considered that since the movement of atoms on a joint surface of the silver brazing is intensified due to the light output and the atoms are pushed by internal pressure and gradually move on the surface of the first window member  21 , the bleed-out phenomenon occurs. 
     As shown in  FIGS.  19 A and  19 B , foreign matter was not generated on the first window member  21  immediately after operation start, and foreign matter was generated on the first window member  21  after an elapse of 46 hours. Foreign matter shown in  FIG.  19 B  is generated in a relatively short time after the start of driving. It is considered that the foreign matter can be generated due to at least one of the following factors. First, it is considered that a factor is the influence of ultraviolet light included in the second light L 2  that is light from the plasma. For example, oxygen in the atmosphere is ozonized by ultraviolet light, so that the silver brazing contained in the joining material can be oxidized in a short time. It is considered that another factor is an increase in the temperature of the light emitting sealed body  1  during driving. During driving, the temperature of the light emitting sealed body  1  rises due to irradiation with laser light and radiant heat from the plasma. 
       FIGS.  20 A to  20 C  are photographs showing a fourth sample immediately after operation start, after an elapse of 147 hours, and after an elapse of 712 hours, respectively.  FIGS.  21 A to  21 C  are photographs showing a fifth sample immediately after operation start, after an elapse of 147 hours, and after an elapse of 712 hours, respectively.  FIGS.  22 A ,  22 B,  23 A, and  23 B are photographs showing a sixth sample immediately after operation start, after an elapse of 168 hours, after an elapse of 504 hours, and after an elapse of 1051 hours, respectively. The fourth sample, the fifth sample, and the sixth sample correspond to the light emitting sealed body  1 . As described above, in the light emitting sealed body  1 , gold-copper brazing is used as the joining material  25 . 
     As shown in  FIGS.  20 A to  20 C and  21 A to  21 C , in the fourth sample and in the fifth sample, foreign matter was not generated on the first window member  21  even after an elapse of 712 hours from the start of driving. As shown in  FIGS.  22 A,  22 B,  23 A, and  23 B , in the sixth sample, foreign matter was not generated on the first window member  21  even after an elapse of 1051 hours from the start of driving. From these results, it can be seen that the generation of foreign matter on the first window member  21  can be suppressed by using a material containing gold as the joining material  25 . 
     As described above, in the light emitting sealed body  1 , the first window member  21  is joined to the housing  10  by the joining material  25  consisting of a material containing gold. Accordingly, the formation of foreign matter on the first window member  21  caused by the joining material  25  can be suppressed as compared to a case where the joining material  25  consists of silver brazing. It is considered that the reason is that since gold having a higher melting point than that of silver brazing is used as the forming material of the joining material  25 , even when the temperature rises due to driving, the movement of the forming material of the joining material  25  on the first window member  21  can be suppressed and, as a result, the occurrence of the bleed-out phenomenon can be suppressed. In addition, it is considered that since gold is less likely to be oxidized than silver, the oxidation of the forming material of the joining material  25  can be suppressed. Therefore, according to the light emitting sealed body  1 , the formation of foreign matter on the first window member  21  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. Note that the inventors of the present application have found that foreign matter can be generated on the first window member  21  because of the forming material of the joining material  25 . 
     The housing  10  (first frame member  61 ) includes the wall portion  65  facing the side surface  21   c  of the first window member  21 , and the joining material  25  joins the side surface  21   c  and the wall portion  65  to each other. Accordingly, the first window member  21  can be reliably joined to the housing  10 . In addition, a region through which light transmits on the first window member  21  can be widely secured, for example, as compared to a case where the first window member  21  is joined to the housing  10  through the first major surface  21   a.    
     The housing  10  includes the flange portion  66  protruding from the wall portion  65 , and the first window member  21  is disposed such that the first major surface  21   a  faces the flange portion  66 . Accordingly, the first window member  21  can be reliably joined to the housing  10 . In addition, the contact of impure gas with a joint portion (metallized layer  26 ) between the first window member  21  and the housing  10  can be suppressed, and the deterioration (for example, oxidation) of the joint portion caused by the impure gas can be suppressed. 
     The joining material  25  is inserted between the first major surface  21   a  of the first window member  21  and the flange portion  66 . Accordingly, the contact of impure gas with the joint portion between the first window member  21  and the housing  10  can be suppressed, and the deterioration of the joint portion caused by the impure gas can be suppressed. 
     The joining material  25  is inserted between the first major surface  21   a  of the first window member  21  and the flange portion  66  in a state where the joining material  25  is not bonded to the first major surface  21   a  of the first window member  21 . Accordingly, since the joining material  25  is not bonded to the first major surface  21   a  of the first window member  21 , the strain caused by a difference in thermal expansion coefficient between the first window member  21  and the flange portion  66  can be reduced. 
     The joining material  25  covers a part of the second surface  66   b  (surface on the side opposite to the first window member  21 ) of the flange portion  66 . Accordingly, the release of impure gas from the second surface  66   b  of the flange portion  66  can be suppressed. 
     The joining material  25  is provided to reach the end surface  65   b  of the wall portion  65  in the Z direction (direction perpendicular to the first major surface  21   a ). Accordingly, the release of impure gas from the end surface  65   b  of the wall portion  65  can be suppressed. Namely, for example, when the end surface  65   b  is a processed metal surface, large irregularities are likely to be formed on the end surface  65   b , and impure gas adsorbed in the irregularities is likely to be released. In this respect, such release of impure gas can be suppressed by covering at least a part of the end surface  65   b  with the joining material  25 . 
     The metallized layer  26  is formed on the first window member  21 , the plating layer  27  is formed on the metallized layer  26 , and the joining material  25  is joined to the plating layer  27 , so that the first window member  21  is joined to the housing  10 . Accordingly, the first window member  21  can be reliably joined to the housing  10 . In addition, the metallized layer  26  has high reactivity, but since the plating layer  27  is formed on the metallized layer  26 , the deterioration (for example, oxidation) of the metallized layer  26  can be suppressed. 
     The plating layer  27  covers the metallized layer  26  such that the metallized layer  26  is not exposed. Accordingly, the metallized layer  26  has high reactivity, but since the plating layer  27  is formed on the metallized layer  26 , the deterioration of the metallized layer  26  can be suppressed. 
     The joining material  25  covers the metallized layer  26  and the plating layer  27  on the internal space S 1  side such that the metallized layer  26  and the plating layer  27  are not exposed. Accordingly, the deterioration of the metallized layer  26  can be further suppressed. 
     The joining material  25  covers the metallized layer  26  and the plating layer  27  on the side opposite the internal space S 1  such that the metallized layer  26  and the plating layer  27  are not exposed. Accordingly, the deterioration of the metallized layer  26  can be further suppressed. 
     The metallized layer  26  is made of molybdenum-manganese. Accordingly, since molybdenum-manganese has a higher melting point than that of gold contained in the joining material  25 , the diffusion of the forming material of the metallized layer  26  into the joining material  25  during manufacturing (for example, when the joining material  25  is baked) can be suppressed. 
     The first window member  21  is made of sapphire. In this case, since a transmittance of sapphire to ultraviolet light is relatively high, light including ultraviolet light can be incident on the first window member  21 . On the other hand, as described above, when light including ultraviolet light is incident on the first window member  21 , foreign matter is likely to be generated on the first window member  21  because of the oxidation of the forming material of the joining material  25 . In this respect, according to the light emitting sealed body  1 , also in such a case, the generation of foreign matter on the first window member  21  can be suppressed. 
     The joining material  25  consists of gold-copper brazing. Accordingly, the generation of foreign matter on the first window member  21  can be reliably suppressed. 
     The housing  10  includes the first frame member  61  fixed to the housing body  11  at the first opening  12 , and the first window member  21  is joined to the first frame member  61  by the joining material  25 . Accordingly, the first window member  21  can be satisfactorily joined to the housing  10 . 
     The housing  10  is made of a metal material. In this case, the charging pressure of the light-emitting gas GS can be increased, and the intensity of the second light L 2  emitted from the second window portion  30  can be increased, whereas foreign matter is likely to be formed on the first window member  21 . The reason is that as the intensity of the second light L 2  increases, ultraviolet included in the second light L 2  also increases. In this respect, according to the light emitting sealed body  1 , also in such a case, the generation of foreign matter on the first window member  21  can be suppressed. 
     The charging pressure of the light-emitting gas GS in the housing  10  is 3 MPa or more. In this case, the brightness of the plasma generated in the light-emitting gas GS can be increased, so that the intensity of the second light L 2  emitted from the second window portion  30  can be increased. On the other hand, since the temperature of the light emitting sealed body  1  when driven rises due to an increase in light output, foreign matter is likely to be generated on the first window member  21 . In this respect, according to the light emitting sealed body  1 , also in such a case, the generation of foreign matter on the first window member  21  can be suppressed. 
     As a third modification example, the joining material  25  may be gold-nickel brazing. Also, in the third modification example, similarly to the first embodiment, the generation of foreign matter on the first window member  21  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. 
     This point will be described with reference to  FIGS.  24 A to  25 B .  FIGS.  24 A,  24 B,  25 A, and  25 B  are photographs showing a seventh sample immediately after operation start, after an elapse of 168 hours, after an elapse of 504 hours, and after an elapse of 1051 hours, respectively. The seventh sample corresponds to the third modification example. As shown in  FIGS.  24 A,  24 B,  25 A, and  25 B , in the seventh sample, foreign matter was not generated on the first window member  21  even after an elapse of 1051 hours from the start of driving. 
     As a fourth modification example, the metallized layer  26  may be titanium-doped silver brazing. Also, in the fourth modification example, similarly to the first embodiment, the generation of foreign matter on the first window member  21  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. 
     This point will be described with reference to  FIGS.  26 A to  27 B .  FIGS.  26 A,  26 B,  27 A, and  27 B  are photographs showing an eighth sample immediately after operation start, after an elapse of 168 hours, after an elapse of 504 hours, and after an elapse of 1051 hours, respectively. The eighth sample corresponds to the fourth modification example. As shown in  FIGS.  26 A,  26 B,  27 A, and  27 B , in the eighth sample, foreign matter was not generated on the first window member  21  even after an elapse of 1051 hours from the start of driving. 
     In the first embodiment, the first window member  21  is made of sapphire, but as another modification example, the first window member  21  may be made of a material other than sapphire, for example, diamond. When the first window member  21  is made of diamond, it is preferable that the metallized layer  26  is made of a material other than molybdenum-manganese, and for example, the metallized layer  26  may be titanium-doped silver brazing as in the fourth modification example. The reason is that the metallized layer  26  made of molybdenum-manganese is difficult to form on the window member made of diamond. 
     In the first embodiment, the joining material  25  that joins the first window member  21  to the housing  10  consists of a material containing gold, but in addition to or instead of this configuration, the joining material  35  that joins the second window member  31  to the housing  10  (second frame member  71 ) may consist of a material containing gold. In this case, the formation of foreign matter on the second window member  31  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. Namely, at least one of the joining material  25  and the joining material  35  may consist of a material containing gold. Similarly to the second window member  31 , the protective layer  80  may be formed at least on the surface on the internal space S 1  side (second major surface  21   b ) of the first window member  21 . In the first embodiment, the first light L 1  is incident on the first opening  12 , and the second light L 2  is emitted from the second opening  13 , but one opening may be formed in the housing  10 , the first light L 1  may be incident on the opening, and the second light L 2  may be emitted from the opening. Namely, the opening of the housing  10  may be such that the first light L 1  is incident thereon and the second light L 2  is emitted therefrom. In this case, a window member that transmits the first light L 1  and the second light L 2  is disposed in the opening. In such a configuration, the window member may be joined to the housing  10  by a joining material consisting of a material containing gold. 
     The first window member  21  and the first frame member  61  (housing  10 ) may be joined by the joining material  25 , and for example, the joining material  25  may be disposed only between the side surface  21   c  of the first window member  21  and the wall portion  65  of the first frame member  61 . In the first embodiment, the first window member  21  is fixed to the housing body  11  via the first frame member  61 , but the first frame member  61  may be omitted and the first window member  21  may be directly fixed to the housing body  11 . In this case, for example, the first window member  21  may be disposed on the inner portion  12   a  of the first opening  12 , or a portion of the housing body  11  may form a wall portion facing the side surface  21   c  of the first window member  21 , the portion forming the inner portion  12   a , and the side surface  21   c  and the wall portion may be joined by the joining material  25 . 
     [Sealed Portion of Charging Pipe] 
     As shown in  FIGS.  1 ,  3 , and  28   , the second end portion  17   b  of the charging pipe  17  is sealed by being crushed. When the housing  10  is charged with the light-emitting gas GS, the second end portion  17   b  is sealed (cut in a sealed state) by introducing the light-emitting gas GS into the housing  10  through the charging pipe  17  and then press-cutting (cutting off) the charging pipe  17  while pressing and crushing a second end portion  17   b  side using a tool or the like. As a result, a pipe material  17   b   1  forming the second end portion  17   b  comes into contact with each other, so that the charging pipe  17  is closed at the second end portion  17   b  by the charging pipe  17  itself. 
     The second end portion  17   b  of the charging pipe  17  is covered with a covering member  91 . The covering member  91  covers a part on the second end portion  17   b  side of the charging pipe  17  and covers the entirety of the second end portion  17   b . The covering member  91  is formed in a substantially cylindrical shape and has a tapered surface  91   a  on an outer surface of a bottom portion of the covering member  91 . The tapered surface  91   a  is formed to decrease in diameter as going away from the second end portion  17   b . The covering member  91  functions as a leakage prevention member that prevents the light-emitting gas GS from leaking from the second end portion  17   b.    
     The covering member  91  is covered with a cap member  92 . The cap member  92  covers an entire surface of the covering member  91  except for a top surface  91   b . The top surface  91   b  is a surface of the covering member  91  on a side opposite to the tapered surface  91   a , and is a surface facing the housing  10 . The cap member  92  is formed in a substantially cylindrical shape and has a tapered surface  92   a  on an inner surface of a bottom portion of the cap member  92 . The tapered surface  92   a  is in contact with the tapered surface  91   a , and is formed to decrease in diameter as going away from the second end portion  17   b . The cap member  92  functions as a protective member that protects the second end portion  17   b  and the covering member  91 . 
     The covering member  91  is made of an inorganic material, and the cap member  92  is made of a metal material. In this example, the charging pipe  17  is made of copper, the covering member  91  is made of solder, and the cap member  92  is made of brass. In this case, a thermal expansion coefficient of the charging pipe  17  is 17.7×10 −6  (1/K), a thermal expansion coefficient of the covering member  91  is 20.2×10 −6  (1/K), and a thermal expansion coefficient of the cap member  92  is 18.0×10 −6  (1/K). Namely, in this example, the thermal expansion coefficient is larger in the order of the covering member  91 , the cap member  92 , the charging pipe  17 . A hardness (Vickers hardness) of the charging pipe  17  is 70 to 80 HV, a hardness of the covering member  91  is approximately 20 HV, and a hardness of the cap member  92  is approximately 180 to 230 HV. Namely, in this example, the hardness is larger in the order of the cap member  92 , the charging pipe  17 , and the covering member  91 . 
     As described above, in the light emitting sealed body  1 , the second end portion  17   b  of the charging pipe  17  which is sealed by being crushed is covered with the covering member  91  made of an inorganic material. Accordingly, the second end portion  17   b  can be prevented from being opened, and even if a leakage from the second end portion  17   b  occurs, the reduction of the charging pressure of the light-emitting gas GS inside the housing  10  can be suppressed. In addition, since the covering member  91  is made of an inorganic material, the covering member  91  can stably cover the second end portion  17   b  even under a high temperature environment. In addition, in the light emitting sealed body  1 , the covering member  91  is covered with the cap member  92  made of a metal material. Accordingly, the second end portion  17   b  and the covering member  91  can be protected. In addition, when the temperature rises, the covering member  91  can tend to be deformed toward the second end portion  17   b  side instead of toward a cap member  92  side. As a result, the second end portion  17   b  can be pressed by the covering member  91 , and the second end portion  17   b  can be further prevented from being opened. Therefore, according to the light emitting sealed body  1 , the leaking of the light-emitting gas GS caused by the opening of the second end portion  17   b  of the charging pipe  17  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. Incidentally, in the laser excitation light source, the light-emitting gas is charged at high pressure for high efficiency and high output, and during driving, the temperature rises due to irradiation with laser light and radiant heat from the plasma. For this reason, when the laser excitation light source is continuously driven for a long time, there is a possibility that the sealed end portion of the charging pipe is expanded and opened and the light-emitting gas leaks. In this respect, according to the light emitting sealed body  1 , as described above, the leaking of the light-emitting gas GS caused by the opening of the second end portion  17   b  of the charging pipe  17  can be suppressed, and the life span of the light emitting sealed body  1  can be extended. 
     The thermal expansion coefficient of the covering member  91  is larger than the thermal expansion coefficient of the charging pipe  17 . Accordingly, when the temperature rises, the second end portion  17   b  of the charging pipe  17  can be effectively pressed by the covering member  91 , and the second end portion  17   b  can be further prevented from being opened. 
     The hardness of the cap member  92  is larger than the hardness of the charging pipe  17 . Accordingly, when the temperature rises, the covering member  91  can tend to be deformed toward the second end portion  17   b  side instead of toward the cap member  92  side, and the second end portion  17   b  can be further prevented from being opened. 
     The covering member  91  is made of a thermoplastic material (solder in the above-described example). Accordingly, it is possible to suitably achieve the above-described functions and effects such as being able to prevent the second end portion  17   b  from being opened, being able to suppress the reduction of the charging pressure of the light-emitting gas GS inside the housing  10  even if a leakage from the second end portion  17   b  occurs, and being able to stably cover the second end portion  17   b  even under a high temperature environment. 
     The cap member  92  is made of brass. Accordingly, it is possible to suitably achieve the above-described functions and effects such as being able to protect the second end portion  17   b  and the covering member  91  and being able to further prevent the second end portion  17   b  from being opened by pressing the second end portion  17   b  using the covering member  91 . 
     The charging pressure of the light-emitting gas GS in the housing  10  is 3 MPa or more. In this case, the intensity of the plasma generated in the light-emitting gas GS can be increased, whereas the second end portion  17   b  of the charging pipe  17  is likely to be opened; however, according to the light emitting sealed body  1 , also in such a case, the second end portion  17   b  can be prevented from being opened. 
     The materials of the charging pipe  17 , the covering member  91 , and the cap member  92  are not limited to the above-described examples, and these components may be made of any material. 
     Second Embodiment 
     As shown in  FIGS.  29  to  32   , a light emitting sealed body  1 A according to a second embodiment further includes a getter portion  101 . In  FIG.  29   , the getter portion  101  is schematically shown. In the light emitting sealed body  1 A, the protective layer  80  is not formed on the second window member  31 . The getter portion  101  includes a getter material  110  and a support member  120  that supports the getter material  110 . The getter material  110  is heated and activated to adsorb impure gas existing in the internal space  51 . The getter material  110  is made of, for example, a material containing nichrome and is configured as a non-evaporable type. Namely, in this example, the getter material  110  does not evaporate when heated and activated. The getter material  110  is activated by being heated to, for example, 250° C. or higher. The getter material  110  is formed in, for example, a rectangular plate shape. 
     The support member  120  is formed from, for example, a metal material in a rectangular plate shape having a larger outer shape than that of the getter material  110 . Examples of the metal material forming the support member  120  include high-melting point metals such as tungsten and molybdenum. 
     The getter material  110  is disposed on the support member  120  and is fixed to the support member  120  by three fixation members  121 . The fixation members  121  are formed from, for example, nickel in a band shape (ribbon shape). Each of the fixation members  121  is disposed to press the getter material  110  at an intermediate portion thereof and is fixed to the support member  120  at both end portions thereof, for example, by welding. Accordingly, the getter material  110  is fixed to the support member  120 . In  FIG.  30   , the getter material  110  is hatched for ease of understanding. 
     The support member  120  is fixed to the housing body  11  (housing  10 ) by four fixation members  122 . The fixation members  122  are formed from, for example, nickel in a band shape (ribbon shape). Each of the fixation members  122  includes an extending portion  122   a  extending from a corner portion of the support member  120  perpendicularly to the support member  120 . The extending portion  122   a  is fixed to the housing body  11 , for example, by welding. In addition, the fixation members  122  are fixed to the support member  120 , for example, by welding. Accordingly, the support member  120  is fixed to the housing body  11 . 
     The getter portion  101  is disposed in an irradiation region RG of the first light L 1  inside the housing  10 .  FIG.  29    shows the irradiation region RG of the first light L 1 . As shown in  FIG.  29   , for example, the first light L 1  that has transmitted through the first window portion  20  converges such that the focal point is located on the intersection point C (generation position of the second light L 2 ) of the first optical axis A 1  and the second optical axis A 2 . The first light L 1  that has passed through the intersection point C travels to a side opposite the first window portion  20  (upper side in  FIG.  29   ) while expanding. In this example, the getter portion  101  (the getter material  110  and the support member  120 ) is disposed on the first optical axis A 1  of the first light L 1 . 
     The getter portion  101  is disposed such that the getter material  110  faces the side opposite the first window portion  20  (upper side in  FIG.  29   ). Accordingly, the support member  120  is disposed to face a first window portion  20  side, and the support member  120  is irradiated with the first light L 1 . In the light emitting sealed body  1 A, the support member  120  is heated by being irradiated with the first light L 1 , and the getter material  110  is indirectly heated by averaged heat transferred from the support member  120 . 
     The getter portion  101  is disposed such that the getter material  110  faces an inner surface  10   a  of the housing  10 . The inner surface  10   a  is a surface of the housing  10  facing the first window portion  20 . Here, the fact that the inner surface  10   a  faces the first window portion  20  means that the inner surface  10   a  and the first window portion  20  overlap each other in the Z direction (direction parallel to the first optical axis A 1 ), and another member may be disposed between the inner surface  10   a  and the first window portion  20 . In this example, the inner surface  10   a  has a tapered shape in which the diameter decreases as the inner surface  10   a  goes away from the getter portion  101 . 
     The getter portion  101  is disposed to define a space S 2  between the getter portion  101  and the inner surface  10   a . The space S 2  is a part of the internal space S 1 . In this example, the space S 2  is a space having a substantially conical shape in which the diameter decreases as the space S 2  goes away from the getter portion  101 . The space S 2  is not completely separated by the getter portion  101  and is connected to a portion of the internal space S 1  other than the space S 2  via a very small gap. 
     The getter portion  101  is disposed between the generation position (intersection point C of the first optical axis A 1  and the second optical axis A 2 ) of the second light L 2  and the charging hole  16  in the internal space S 1 . As described above, the charging hole  16  also functions as an exhaust hole that discharges gas (impure gas) from the internal space S 1  to the outside when the light emitting sealed body  1 A is manufactured. A distance D 1  from the getter material  110  to the generation position of the second light L 2  is longer than a distance D 2  from the generation position of the second light L 2  to the first window portion  20 . 
     A melting point of the support member  120  is higher than a melting point of the getter material  110 . As one example, the getter material  110 , the support member  120 , the housing body  11 , and the first frame member  61  (second frame member  71 ) are made of nichrome, tungsten, SUS304, and Kovar metal, respectively. Melting points of nichrome, tungsten, SUS304, and Kovar metal are 1400° C., 3387° C., 1400 to 1450° C., and 1450° C., respectively. Namely, in this example, the melting point of the support member  120  is higher than the melting points of the getter material  110 , the housing body  11 , and the first frame member  61 . When the support member  120  is made of molybdenum also, since the melting point of molybdenum is 2623° C., the melting point of the support member  120  is higher than the melting points of the getter material  110 , the housing body  11 , and the first frame member  61 . 
     A thermal conductivity of the support member  120  is higher than a thermal conductivity of the getter material  110 . Thermal conductivities of nichrome, tungsten, SUS304, and Kovar metal are 14 (W/m·K), 168 (W/m·K), 16.7 (W/m·K), and 17 (W/m·K), respectively. Namely, in an example where the getter material  110 , the support member  120 , the housing body  11 , and the first frame member  61  (second frame member  71 ) are made of nichrome, tungsten, SUS304, and Kovar metal, respectively, the thermal conductivity of the support member  120  is higher than the thermal conductivities of the getter material  110 , the housing body  11 , and the first frame member  61 . When the support member  120  is made of molybdenum also, since the thermal conductivity of molybdenum is 142 (W/m·K), the thermal conductivity of the support member  120  is higher than the thermal conductivities of the getter material  110 , the housing body  11 , and the first frame member  61 . 
     When the light emitting sealed body  1 A is driven, as a first step, the getter material  110  is heated and activated by irradiation with the first light L 1  through the first window portion  20 . Subsequently, in a state where the getter material  110  is activated, as a second step, a plasma is generated in the light-emitting gas GS, and the second light L 2  is emitted from the second window portion  30 . Accordingly, impure gas existing in the internal space S 1  can be adsorbed by the activated getter material  110 . The first step and the second step may be sequentially performed as in this example, but may be simultaneously performed. 
     Next, the suppression of defects by the getter portion  101  will be described. In the laser excitation light source, when impure gas exists in the internal space inside the housing, various defects may occur inside the housing. In order to extend the life span of the laser excitation light source, suppressing such defects is required. 
     One of defects caused by impure gas is a phenomenon in which the above-described window member becomes opaque (opacity phenomenon) ( FIGS.  6 A and  6 B ). 
     Another defect caused by impure gas is the generation of foreign matter inside the housing  10 .  FIGS.  33 A and  33 B  are photographs showing an example in which foreign matter is generated on the first electrode  40  and/or on the second electrode  50 . In the photograph shown in  FIG.  33 A , as indicated by arrow AR, foreign matter adheres to the tips of the first electrode  40  and to the second electrode  50 . The foreign matter has, for example, carbon as a main component. In the photograph shown in  FIG.  33 B , as indicated by arrow AR, foreign matter adheres to a side surface of the second electrode  50 . The foreign matter consists of, for example, tungsten oxide. It is considered that the foreign matter is generated due to impure gas existing in the internal space S 1  inside the housing  10 . Since the foreign matter can interfere with the operation of the light emitting sealed body  1 A, suppressing the foreign matter is required. 
       FIGS.  34 A to  34 C  are photographs showing a ninth sample immediately after operation start, after an elapse of 260 hours, and after an elapse of 670 hours, respectively. The ninth sample corresponds to a configuration in which the getter portion  101  is not provided in the light emitting sealed body  1 A. As shown in  FIG.  34 A , foreign matter did not adhere onto the first electrode  40  and onto the second electrode  50  immediately after operation start. As indicated by arrow AR in  FIGS.  34 B and  34 C , foreign matter adhered to the first electrode  40  and to the second electrode  50  after an elapse of 260 hours and after an elapse of 670 hours. 
       FIGS.  35 A to  37 C  are photographs showing a tenth sample immediately before operation start, immediately after operation start, and after an elapse of 165 hours, respectively.  FIGS.  35 A to  37 C  show the first window portion  20 . The focal point is on the first window member  21  in  FIG.  35 A , the focal point is on the first electrode  40  and on the second electrode  50  in  FIG.  35 B , and the focal point is on the support member  120  in  FIG.  35 C . This point is also the same for  FIGS.  36 A to  37 C . The tenth sample corresponds to the light emitting sealed body  1 A. As shown in  FIGS.  35 A to  37 C , even after an elapse of 165 hours from the start of driving, the opacity phenomenon did not occur on the first window member  21 , and foreign matter did not adhere to the first electrode  40  and the second electrode  50 . 
       FIGS.  38 A to  40 B  are photographs showing an eleventh sample immediately before operation start, immediately after operation start, and after an elapse of 165 hours, respectively.  FIGS.  41 A to  43 B  are photographs showing a twelfth sample immediately before operation start, immediately after operation start, and after an elapse of 165 hours, respectively.  FIGS.  38 A to  43 B  show the second window portion  30 . In  FIG.  38 A , the focal point is on the second window member  31 . In  FIG.  38 B , an image of the first electrode  40  and the second electrode  50  is captured through the second window member  31 , and the focal point is on the first electrode  40  and on the second electrode  50 . These points are also the same for  FIGS.  39 A to  44 B . The eleventh sample and the twelfth sample correspond to the light emitting sealed body  1 A. As shown in  FIGS.  38 A to  43 B , in both the eleventh sample and the twelfth sample, even after an elapse of 165 hours from the start of driving, the opacity phenomenon did not occur on the second window member  31 , and foreign matter did not adhere to the first electrode  40  and the second electrode  50 . 
       FIG.  44 A  is a photograph showing a thirteenth sample immediately after operation start, and  FIG.  44 B  is a photograph showing the thirteenth sample after an elapse of 262 hours. The thirteenth sample corresponds to the light emitting sealed body  1 A. As shown in  FIGS.  44 A and  44 B , even after an elapse of 165 from the start of driving, foreign matter did not adhere to the first electrode  40  and the second electrode  50 . 
     From the above results, it can be seen that the occurrence of the opacity phenomenon and the generation of foreign matter inside the housing  10  can be suppressed by providing the getter portion  101 . 
     As described above, in the light emitting sealed body  1 A, the getter portion  101  including the getter material  110  is disposed in the irradiation region RG of the first light L 1  inside the housing  10 . Accordingly, the getter material  110  can be heated and activated by irradiation with the first light L 1 , and impure gas existing in the internal space S 1  can be adsorbed by the activated getter material  110 . As a result, the occurrence of a defect caused by impure gas can be suppressed. In addition, since the getter material  110  is heated and activated by irradiation with the first light L 1 , the heating of a member other than the getter portion  101 , for example, the heating of the housing  10  can be suppressed. As a result, for example, the occurrence of a defect (for example, a leakage of the light-emitting gas GS or the like) caused by an increase in the temperature of the housing  10  can be suppressed. Therefore, according to the light emitting sealed body  1 A, the life span can be extended. 
     The getter portion  101  includes the support member  120  that supports the getter material  110 . Accordingly, for example, the getter material  110  can be indirectly heated through the support member  120 , and the excessive heating of the getter material  110  can be suppressed. 
     The getter portion  101  is disposed such that the getter material  110  faces the side opposite the first window portion  20 . Accordingly, the support member  120  functions as an adhesion prevention plate, and the spattered getter material  110  can be prevented from moving to the first window portion  20  side and from adhering to the first window portion  20  and the like. 
     The getter portion  101  is disposed such that the support member  120  is irradiated with the first light L 1 . Accordingly, the getter material  110  can be indirectly heated through the support member  120 , and the excessive heating of the getter material  110  can be suppressed. 
     The melting point of the support member  120  is higher than the melting point of the getter material  110 . Accordingly, damage to the support member  120  caused by heating through irradiation with the first light L 1  can be suppressed. 
     The thermal conductivity of the support member  120  is higher than the thermal conductivity of the getter material  110 . Accordingly, the getter portion  101  can be efficiently heated through the support member  120 . 
     The getter portion  101  is disposed such that the getter material  110  faces the inner surface  10   a  of the housing  10 , the inner surface  10   a  facing the first window portion  20 . Accordingly, the spattered getter material  110  can adhere to the inner surface  10   a . The getter material  110  that has adhered to the inner surface  10   a  can be heated and activated again by the first light L 1 . As a result, impure gas can be adsorbed by the getter material  110  that has adhered to the inner surface  10   a.    
     The getter portion  101  is disposed to define the space S 2  between the getter portion  101  and the inner surface  10   a  of the housing  10 . Accordingly, the spattered getter material  110  can be kept in the space S 2 , and the adhesion of the getter material  110  to other members can be suppressed. 
     The getter portion  101  is disposed between the generation position (intersection point C of the first optical axis A 1  and the second optical axis A 2 ) of the second light L 2  and the charging hole  16  (exhaust hole) in the internal space S 1 . Gas may be generated from the getter material  110  when the light emitting sealed body  1 A is manufactured, but the gas can be easily discharged from the charging hole  16  to the outside. 
     The distance D 1  from the getter material  110  to the generation position of the second light L 2  is longer than the distance D 2  from the generation position of the second light L 2  to the first window portion  20 . Accordingly, the excessive heating of the getter material  110  can be suppressed. 
     The getter material  110  is configured as the non-evaporable type. Also, in this case, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body  1 A can be extended. The amount of the getter material  110  of the non-evaporable type may be determined in consideration of the degree of vacuum, the life span, or the like of the light emitting sealed body  1 A. 
     The second window portion  30  includes the second window member  31  made of a material containing diamond. In this case, light in a wide wavelength range including ultraviolet light can pass through the second window member  31 . In addition, foreign matter containing carbon is likely to be generated as a defect caused by impure gas, but according to the light emitting sealed body  1 A, also in such a case, the generation of foreign matter can be suppressed. 
     The housing  10  is made of a metal material. In this case, the charging pressure of the light-emitting gas GS can be increased, and the intensity of the second light L 2  emitted from the second window portion  30  can be increased. In addition, as described above, impure gas is likely to exist in the internal space S 1 , but according to the light emitting sealed body  1 A, also in such a case, the occurrence of a defect caused by impure gas can be suppressed. 
     The light emitting sealed body  1 A includes the first electrode  40  and the second electrode  50  that face each other with the generation position of the second light L 2  interposed therebetween. In this case, a plasma can be more reliably generated. In addition, foreign matter caused by impure gas is likely to be generated on the first electrode  40  and the second electrode  50 , but according to the light emitting sealed body  1 A, the generation of foreign matter on the first electrode  40  and the second electrode  50  can be suppressed. 
     The charging pressure of the light-emitting gas GS in the housing  10  is 3 MPa or more. In this case, as described above, the brightness of the plasma generated in the light-emitting gas GS can be increased, so that the intensity of the second light L 2  emitted from the second window portion  30  can be increased. On the other hand, impure gas is likely to exist inside the housing  10 . In this respect, according to the light emitting sealed body  1 A, also in such a case, the occurrence of a defect caused by impure gas can be suppressed. 
     A method for driving the light emitting sealed body  1 A according to the second embodiment includes a step of activating the getter material  110  by irradiating the getter material  110  with the first light L 1 , and a step of generating a plasma in the light-emitting gas GS and of emitting the second light L 2 . In this driving method, the getter material  110  can be heated and activated by irradiation with the first light L 1 , and impure gas existing in the internal space S 1  can be adsorbed by the activated getter material  110 . As a result, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body  1 A can be extended. 
     As in a fifth modification example shown in  FIG.  45   , the getter material  110  may be fixed to an inner surface of the housing  10 . In  FIG.  45   , the getter material  110  is hatched for ease of understanding. In the fifth modification example, the getter portion  101  includes only the getter material  110  and does not include the support member  120  and the like. The inner surface of the housing  10  has an inner peripheral surface  10   b  having a cylindrical shape and extending with a straight line parallel to the first optical axis A 1  of the first light L 1  set as a center line. The getter material  110  is fixed to the inner peripheral surface  10   b . The getter material  110  extends along a circumferential direction to have a cylindrical shape (annular band shape) as a whole, but may have a gap (break) at a part in the circumferential direction. Also, in the fifth modification example, the getter material  110  is disposed in the irradiation region RG of the first light L 1 . More specifically, the getter material  110  is disposed such that a bottom edge of the first light L 1  that is laser light is incident thereon, and is directly heated by irradiation with the first light L 1 . 
     Also, in the fifth modification example, similarly to the second embodiment, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body  1 A can be extended. In addition, the getter material  110  can be heated using the bottom edge of the first light L 1  that is laser light. For this reason, the occurrence of a defect caused by impure gas can be suppressed while suppressing the excessive heating of the getter material  110 . 
     In a sixth modification example shown in  FIG.  46   , the getter material  110  is configured as an evaporable (depositable) type. The getter material  110  of the evaporable type is made of, for example, a material containing barium. When the getter material  110  of the evaporable type is heated and activated, at least a part of the getter material  110  evaporates (barium is emitted). The evaporated getter material  110  is deposited on the inner surface  10   a  of the housing  10 . The deposited getter material  110  forms an adsorption surface for impure gas. When the driving of the light emitting sealed body  1 A is started, the getter material  110  is heated by irradiation with the first light L 1  and is deposited on the inner surface  10   a . Thereafter, a plasma is generated and a part of the first light L 1  is absorbed by the plasma, so that the heating of the getter material  110  is reduced and the deposition is stopped. Since the getter material  110  is heated to form a new adsorption surface at each time of driving, the adsorption surface can be brought into good condition at each time of driving. Also, in the sixth modification example, similarly to the second embodiment, the occurrence of a defect caused by impure gas can be suppressed, and the life span of the light emitting sealed body  1 A can be extended. Incidentally, the amount of the getter material  110  of the evaporable type may be determined in consideration of the degree of vacuum, the life span, or the like of the light emitting sealed body  1 A, and there is no need to necessarily set such an amount that the getter material  110  is heated to form a new adsorption surface at each time of driving. For example, the amount may be set such that the getter material  110  is heated to form a new adsorption surface only during initial driving and several subsequent driving where the amount of release of impure gas considered to be particularly high. In this case, the support member  120  on which the getter material  110  is not left has an effect of shielding and protecting the getter material  110  deposited on the inner surface  10   a  of the housing  10 , from the first light L 1 . 
     As another modification example, similarly to the second embodiment, the getter material  110  may be disposed in the irradiation region RG of the first light L 1  or may be disposed at any position other than the above-described position. At least a part of the getter material  110  may be disposed in the irradiation region RG, for example, the support member  120  may be disposed in the irradiation region RG, whereas the getter material  110  may be disposed outside the irradiation region RG. The getter material  110  may be disposed to face the first window portion  20  side. In this case, the getter material  110  is directly heated by irradiation with the first light L 1 . The distance D 1  from the getter material  110  to the generation position of the second light L 2  may be shorter than the distance D 2  from the generation position of the second light L 2  to the first window portion  20 . In this case, the getter material  110  can be efficiently heated by irradiation with the first light L 1 . In the light emitting sealed body  1 A of the second embodiment, the protective layer  80  may be formed on the second window member  31 . In this case, the occurrence of the opacity phenomenon can be further suppressed. The materials of the getter material  110  and the support member  120  are not limited to the above-described examples, and these components may be made of any material. 
     The present disclosure is not limited to the embodiments and to the modification examples. For example, the material and the shape of each configuration are not limited to the material and the shape described above, and various materials and shapes can be adopted. The shape of the first opening  12 , the second opening  13 , the first window member  21 , and the second window member  31  is not limited to a circular plate shape and may be various shapes. In the above-described examples, the two second openings  13  are formed, but only one second opening  13  may be formed or three or more second openings  13  may be formed. As described above, the first light L 1  may be incident through one opening formed in the housing  10 , and the second light L 2  may be emitted through the one opening. The material forming the housing  10  may not necessarily be a metal material and may be an insulating material, for example, ceramic or the like. The first electrode  40  and the second electrode  50  may be omitted. Also, in this case, a plasma can be generated at a focal point by irradiating the light-emitting gas GS with the condensed first light L 1 . 
     The first window member  21  may be made of diamond, and the second window member  31  may be made of sapphire. Alternatively, both the first window member  21  and the second window member  31  may be made of sapphire or diamond. When ultraviolet light is used, the first window member  21  and/or the second window member  31  may be made of magnesium fluoride or quartz. The first window member  21  and/or the second window member  31  may be made of Kovar glass. The first window member and the second window member may be configured to be the same window member. Namely, the first light L 1  and the second light L 2  may be configured to pass through the same window member. The first window member, the second window member, and the housing  10  may be integrally made of a light transmissive material. In this case, in a light-transmitting region on the housing  10 , a region through which the first light L 1  passes can be regarded as the first window member (first window portion), and a region through which the second light L 2  passes can be regarded as the second window member (second window portion). When the first window member  21  is made of diamond, the protective layer  80  may be formed on the surface on the internal space S 1  side (second major surface  21   b ) of the first window member  21 . The protective layer  80  may not be formed on the second window member  31 . The joining material  25  may be titanium-doped silver brazing. The second end portion  17   b  of the charging pipe  17  may not be covered with the covering member  91  and with the cap member  92 . Namely, at least one of the covering member  91  and the cap member  92  may be omitted. In this specification, “A and/or B” means “at least one of A and B”.