Patent Publication Number: US-2022224072-A1

Title: Laser module

Description:
TECHNICAL FIELD 
     The present disclosure relates to a laser module. This application claims priority to Japanese Patent Application No. 2019-111892 filed on Jun. 17, 2019, which is hereby incorporated in its entirety. 
     BACKGROUND ART 
     Examples of the light source device include a device in which a laser diode corresponding to a light emitting element and a lens for collimating laser light from the laser diode are mounted on a substrate. Japanese Patent Application Laid-Open No. 2004-289010 discloses that the vapor pressure of the Si organic compound gas in the package is set to 5.4×10 2 N/m 2  or less from the viewpoint of suppressing the characteristic deterioration of the light source device. In Japanese Patent Application Laid-Open No. 2004-289010, using an adhesive having a small amount of volatile gas for adjusting the vapor pressure is used. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Publication No. 2004-289010 
     SUMMARY OF INVENTION 
     A laser module according to an aspect of the present disclosure includes a base, a carrier mounted on the base, a laser diode mounted on the carrier, an organic adhesive layer provided between the laser diode and the carrier, the organic adhesive layer having an exposed portion exposed between the laser diode and the carrier, a cap fixed to the base, the cap covering the carrier, the laser diode, and the organic adhesive layer, and a cover material covering at least a part of the exposed portion of the organic adhesive layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a laser module according to an first embodiment. 
         FIG. 2  is a perspective view showing a state in which a cap is removed from the laser module of  FIG. 1 . 
         FIG. 3  is a plan view of  FIG. 2 . 
         FIG. 4A  is a side view of  FIG. 2 . 
         FIG. 4B  is a schematic enlarged sectional view of a portion indicated by a broken line in  FIG. 4A . 
         FIG. 5  is a schematic cross-sectional view showing a laser light emitting end face of an LD according to a reference example. 
         FIG. 6A  is a graph showing an output variation accompanying the use of the laser module according to the comparative example. 
         FIG. 6B  is a graph showing an output variation associated with the use of the laser module according to the first embodiment. 
         FIG. 7  is a view showing the results of measuring the carrier surfaces of the laser modules according to the comparative example and the first embodiment by TOF-SIMS. 
         FIG. 8A  is an enlarged cross-sectional view of a main part of a laser module according to a first modification. 
         FIG. 8B  is an enlarged cross-sectional view of a main part of a laser module according to a second modification. 
         FIG. 9A  is an enlarged cross-sectional view of a main part of the laser module according to the second embodiment. 
         FIG. 9B  is an enlarged cross-sectional view of a main part of a laser module according to a modification of the second embodiment. 
         FIG. 10A  is a perspective view illustrating a state in which a cap is removed from the laser module according to the third embodiment. 
         FIG. 10B  is an enlarged cross-sectional view of a main part of  FIG. 10A . 
         FIG. 11A  is a perspective view showing a laser module according to the fourth embodiment. 
         FIG. 11B  is a perspective view showing a state in which the cap is removed from the laser module of  FIG. 11B . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     [Problems to Be Solved by Disclosure] 
     In the case where an adhesive layer including an adhesive whose amount of volatile gas is small is used, a variety of an organic compound included in the adhesive layer is limited. Thus, for example, problems such as loss of freedom of design occur. In view of such problems, it is an object of the present disclosure to provide a laser module capable of suppressing characteristic deterioration due to gas of an organic compound without limiting the variety of the organic compound included in an adhesive layer. 
     [Effects of the Present Disclosure] 
     According to the present disclosure, it is possible to provide a laser module capable of suppressing characteristic deterioration due to gas of an organic compound without limiting the variety of the organic compound included in an adhesive layer. 
     [Description of Embodiments of Present Disclosure] 
     First, contents of embodiments of the present disclosure will be listed and described. An embodiment of the present disclosure is a laser module including a base, a carrier mounted on the base, a laser diode mounted on the carrier, an organic adhesive layer provided between the laser diode and the carrier, the organic adhesive layer having an exposed portion exposed from between the laser diode and the carrier, a cap fixed to the base, the cap covering the carrier, the laser diode, and the organic adhesive layer, and a cover material covering at least a part of the exposed portion of the organic adhesive layer. 
     In this laser module, at least a part of an exposed portion of the organic adhesive layer, which is exposed between the carrier and the laser diode, is covered with a cover material. Such a cover material can prevent an organic compound included in the organic adhesive layer from volatilizing into an interior space defined by the base and the cap. Thus, vapor pressure of organic compound gas in the interior space can be reduced without limiting the components of the organic compound included in the organic adhesive layer. Therefore, according to the laser module, it is possible to suppress the characteristic deterioration due to the gas of the organic compound without limiting the variety of the organic compound included in the organic adhesive layer. 
     In one embodiment, the emission wavelength of the laser diode may be 500 nm or less. The characteristic deterioration of the laser diode due to the volatilized organic compound gas is likely to be more remarkable as the emission wavelength of the laser diode is shorter. Therefore, by using the laser module, the laser diode can exhibit good characteristics for a long time even when the emission wavelength of the laser diode is 500 nm or less. 
     Another embodiment of the present disclosure is a laser module including a base, a carrier mounted on the base, an organic adhesive layer provided between the carrier and the base, the organic adhesive layer having an exposed portion exposed from between the carrier and the base, a cap fixed to the base, the cap covering the carrier, the laser diode, and the organic adhesive layer, and a cover material covering at least a part of the exposed portion of the organic adhesive layer. 
     In this laser module, at least a part of an exposed portion of the organic adhesive layer exposed between the carrier and the base is covered with a cover material. Such a cover material can prevent an organic compound included in the organic adhesive layer from volatilizing into an interior space defined by the base and the cap. Therefore, vapor pressure of gas of the organic compound in the interior space can be reduced without limiting the components of the organic compound included in the organic adhesive layer. Therefore, according to the laser module, it is possible to suppress the characteristic deterioration due to the gas of the organic compound without limiting the variety of the organic compound included in the organic adhesive layer. 
     In one embodiment, the cover material may also cover at least a part of the base. In this case, since the cover material is less likely to be peeled off, the function of preventing volatilization of the organic compound gas obtained by the cover material can be maintained for a long time. In addition, since volatilization of the organic compound attached to a surface of the base can be suppressed, the vapor pressure of the organic compound gas in the interior space can be favorably reduced. Moreover, a temperature adjust element may be provided inside the carrier. 
     Still another embodiment of the present disclosure is a laser module including a base, a carrier mounted on the base, a laser diode mounted on the carrier, an optical element mounted on the carrier, an organic adhesive layer provided between the optical element and the carrier, the organic adhesive layer having an exposed portion exposed between the optical element and the carrier, a cap fixed to the base, the cap covering the carrier, the laser diode, the optical element and the organic adhesive layer, and a cover material covering at least a part of the exposed portion of the organic adhesive layer. 
     In this laser module, at least a part of an exposed portion of the organic adhesive layer, which is exposed between the carrier and the optical element, is covered with a cover material. Such a cover material can prevent an organic compound included in the organic adhesive layer from volatilizing into an interior space defined by the base and the cap. Thus, vapor pressure organic compound gas in the interior space can be reduced without limiting the components of the organic compound included in the organic adhesive layer. Therefore, according to the laser module, it is possible to suppress the characteristic deterioration due to the gas of the organic compound without limiting the variety of the organic compound included in the organic adhesive layer. 
     In one embodiment, the cover material may also cover at least a part of the carrier. In this case, since the cover material is less likely to be peeled off, the function of preventing volatilization of the organic compound gas obtained by the cover material can be maintained for a long time. Moreover, since volatilization of the organic compound attached to the surface of the carrier can be suppressed, the vapor pressures of the organic compound gas in the interior space can be favorably reduced. 
     In one embodiment, the cover material may cover whole of the exposed portion of the organic adhesive layer. In this case, volatilization of the organic compound gas into the interior space can be favorably suppressed. 
     In one embodiment, the cover material may include silicon oxide. In this case, the organic adhesive layer may include the organic compound including at least one of Si and O, and the silicon oxide may include at least one of Si and O included in the organic compound. In this case, since the silicon oxide included in the cover material can have a dense molecular structure, volatilization of the organic compound gas from the organic adhesive layer can be favorably suppressed. 
     [Description of Embodiments of Present Disclosure] 
     A specific example of a laser module according to an embodiment of the present disclosure will be described below with reference to the figures. Note that the present disclosure is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims In the following description, the similar elements or elements having the same function will be denoted by the same reference symbol, and an overlapping description will be omitted. 
     First Embodiment 
       FIG. 1  is a perspective view illustrating a laser module according to an first embodiment.  FIG. 2  is a perspective view showing a state in which a cap is removed from the laser module of  FIG. 1 .  FIG. 3  is a plan view of  FIG. 2 .  FIG. 4A  is a side view of  FIG. 2 . The laser module  1  shown in  FIGS. 1 to 4A  is a light source device that oscillates laser light L, and is used in, for example, a head-up display mounted on a vehicle. The laser light L is, for example, multiplexed light multiplexed in the laser module  1 . The laser module  1  includes a base  2  as a part of a package, a light source portion  3 , and a cap  4  as another part of the package. The package is an exterior of the laser module  1 . 
     Hereinafter, the emission direction of the laser light L in a plan view is referred to as a direction X, the direction intersecting or orthogonal to the direction X in a plan view is referred to as a direction Y, and the direction intersecting or orthogonal to the directions X and Y in a plan view is referred to as a direction Z. In the first embodiment, the directions X, Y, and Z are orthogonal to each other, and the direction Z corresponds to a direction in which base  2  and cap  4  overlap. The plan view corresponds to a view from the direction Z. 
     The base  2  is a member having a primary face  2   a  on which the light source portion  3  is placed. A plurality of lead pins  5  extending in the direction Z are passed through the base  2 . The plurality of lead pins  5  are members for connecting the light source portion  3  and an external device. The plurality of lead pins  5  include, for example, a signal supply lead pin, a current supply lead pin, and a GND lead pin. 
     For example, a part of the plurality of lead pins  5  is located on one side of the light source portion  3  in the direction Y, and the other part of the plurality of lead pins  5  is located on the other side of the light source portion  3  in the direction Y. Each lead pin  5  is electrically insulated from the base  2 . On the primary face  2   a , a wiring and the like for connecting the light source portion  3  and the lead pin  5  is actually provided, but illustration thereof is omitted. Similarly, the wiring and the like included in the light source portion  3  are not shown. 
     The light source portion  3  is a portion that emits laser light L, and includes a thermo-electric cooler (TEC)  11 , a carrier  13 , laser diodes (LDs)  14  to  16 , a thermistor  17 , lenses  18  to  20 , and a multiplex optical system  21 . 
     The TEC  11  is a temperature adjusting element that adjusts the temperature of the LDs  14  to  16  and the like, and is fixed to the primary face  2   a  of the base  2 . The TEC  11  is, for example, a Peltier element. The TEC  11  is fixed to the base  2  via an adhesive such as silver (Ag) paste. In the present specification, an adhesive or the like may be or may not be used for fixing different members to each other. 
     The TEC  11  includes substrates  12   a  and  12   b  and a thermoelectric element  12   c  located between the substrates  12   a  and  12   b . The substrate  12   a  is a member fixed to the base  2  via the adhesive. The substrate  12   b  is a member that supports the carrier  13 , the LDs  14  to  16 , the thermistor  17 , the lenses  18  to  20 , and the multiplex optical system  21 , and is disposed on the substrate  12   a  via the thermoelectric element  12   c . Each of the substrates  12   a  and  12   b  has, for example, a quadrangular shape in a plan view. The substrates  12   a  and  12   b  exhibit an insulating property. The substrates  12   a  and  12   b  are ceramic substrates such as alumina substrates and AlN substrate. The substrates  12   a  and  12   b  and the thermoelectric element  12   c  such as BiTE are fixed via, for example, metal electrodes evaporated on the surfaces of the substrates  12   a  and  12   b  and solder (not shown). The metal electrodes are, for example, Au electrodes, and the solder is, for example, AuSn or SNsb. 
     The carrier  13  is a member that supports the LDs  14  to  16 , the thermistor  17 , the lenses  18  to  20 , and the multiplex optical system  21 , and is fixed on the TEC  11 . The carrier  13  is fixed to the TEC  11  via an adhesive such as Ag paste. The carrier  13  has, for example, substantially the same shape as the substrate  12   b  of the TEC  11  in a plan view. The carrier  13  is made of, for example, metal or ceramics. The metal forming the carrier  13  is, for example, Cu, and the ceramic forming the carrier  13  is, for example, AlN. When the carrier  13  is made of a ceramic, a conductive member may be provided in the carrier  13 . The carrier  13  includes a first portion  13   a  on which the LDs  14  to  16  and the thermistor  17  are mounted, and a second portion  13   b  on which the lenses  18  to  20  and the multiplex optical system  21  are mounted. The first portion  13   a  and the second portion  13   b  are arranged along the direction Y. A step is formed by the first portion  13   a  and the second portion  13   b . In the first embodiment, from the viewpoint of optimizing the optical coupling between the LDs  14  to  16  and the lenses  18  to  20 , a thickness of the first portion  13   a  along the direction Z is larger than a thicknesses of the second portion  13   b  along the direction Z. Therefore, in the direction Z, the interval between the base  2  and the LDs  14  to  16  is larger than the interval between the base  2  and the lenses  18  to  20 . 
     The LDs  14  to  16  are light oscillation devices that emit laser lights of different colors respectively, and are arranged in parallel in the direction X. The LDs  14  to  16  are arranged in order along the direction X. Each of the optical axes of the LDs  14  to  16  extends along the direction Y. The optical axes of the LDs  14  to  16  are substantially parallel to each other. 
     The LD  14  is an optical oscillator that emits red laser light L 1 , and is mounted on the carrier  13 . The wavelength range of the red laser light L 1  emitted from the LD  14  is, for example, 610 nm to 670 nm. The LD  14  includes a submount  14   a  mounted on the carrier  13  and a laser oscillator  14   b  fixed on the submount  14   a . The submount  14   a  is a member provided between the carrier  13  and the laser oscillator  14   b , and is provided on the first portion  13   a . The submount  14   a  includes, for example, a material having a thermal expansion coefficient close to that of a material included in the laser oscillator  14   b . Examples of the material include aluminum nitride (AlN), silicon carbide (SiC), silicon (Si), and diamond. The submount  14   a  is fixed to the carrier  13  via an organic adhesive layer  31  (described in detail later). The laser oscillator  14   b  is a semiconductor device mounted on the carrier  13  via a submount  14   a . The laser oscillator  14   b  includes, for example, a GaAs-based semiconductor. 
     The LD  15  is an optical oscillation device that emits green laser light L 2 , and is mounted on the carrier  13 . The wavelength range of the green laser light L 2  emitted from the LD  15  is, for example, 500 nm to 550 nm. The LD  15  includes a submount  15   a  mounted on the carrier  13  and a laser oscillator  15   b  fixed on the submount  15   a . The submount  15   a  is a member provided between the carrier  13  and the laser oscillator  15   b , and is provided on the first portion  13   a . The submount  15   a  includes, for example, a material similar to that of the submount  14   a , and is fixed to the carrier  13  via an adhesive layer similar to that of the organic adhesive layer  31 . The laser oscillator  15   b  is a semiconductor device mounted on the carrier  13  via a submount  15   a . The laser oscillator  15   b  includes, for example, a GaN-based semiconductor. 
     The LD  16  is an optical oscillator that emits blue laser light L 3 , and is mounted on the carrier  13 . The wavelength range of the blue laser light L 3  emitted from the LD  16  is 500 nm or less, for example, 410 nm to 460 nm. The LD  16  includes a submount  16   a  mounted on the carrier  13  and a laser oscillator  16   b  fixed on the submount  16   a . The submount  16   a  is a member provided between the carrier  13  and the laser oscillator  16   b , and is provided on the first portion  13   a . The submount  16   a  includes, for example, the same material as the submounts  14   a  and  15   a , and is fixed to the carrier  13  via an adhesive layer similar to the organic adhesive layer  31 . The laser oscillator  16   b  is a semiconductor device mounted on the carrier  13  via a submount  16   a . The laser oscillator  16   b  includes, for example, a GaN-based semiconductor. 
     The thermistor  17  is a sensor for detecting the temperature of the carrier  13 . The thermistor  17  is fixed to the carrier  13  via an adhesive such as Ag paste. In a case where the carrier  13  exhibits an insulating property, a case where wire bonding to the carrier  13  is difficult, or the like, the thermistor  17  is installed on an insulating submount provided on the carrier  13 , for example. The metal electrode provided on the surface of the submount is wire-bonded to the thermistor  17 . 
     Lenses  18  to  20  are optical elements arranged so as to correspond to the LDs  14  to  16 . In the first embodiment, the lenses  18  to  20  are collimator lenses that collimate (parallelize) laser light from the corresponding LDs  14  to  16 , respectively. In the first embodiment, the lens  18  is disposed on the optical path of the LD  14 , the lens  19  is disposed on the optical path of the LD  15 , and the lens  20  is disposed on the optical path of the LD  16 . Therefore, the lenses  18  to  20  are optically coupled to the LDs  14  to  16 , respectively. The focal lengths of the lenses  18  to  20  are, for example, less than 5 mm. 
     The lens  18  has a lens function region  18   a  for collimating laser light and a holding region  18   b  for holding the lens function region  18   a . The shape of the lens  18  is not particularly limited as long as it has a collimating function. The lens  18  is, for example, a molded product in which a lens function region  18   a  and a holding region  18   b  are integrally molded. When the material of the lens  18  is a resin, the resin is, for example, a cycloolefin polymer. The lens  18  is fixed to the carrier  13  via, for example, an adhesive. Like the lens  18 , the lenses  19 , 20  and have lens function regions  19   a  and  20   a  and holding regions  19   b  and  20   b , respectively. 
     The multiplex optical system  21  includes  3  wavelength selection filters  22  to  24 . Each of the wavelength selection filters  22  to  24  is a type of optical element and is, for example, a multilayer film filter formed on a glass substrate. For example, one or more dielectric thin films are formed on each of the wavelength selection filters  22  to  24 . The wavelength selection filters  22  to  24  are arranged so as to correspond to the lenses  18  to  20 , respectively. Therefore, the wavelength selection filters  22  to  24  are arranged so as to correspond to the LDs  14  to  16 , respectively. In the first embodiment, the wavelength selection filter  22  is located on the optical path of the red laser light L 1 , the wavelength selection filter  23  is located on the optical path of the green laser light L 2 , and the wavelength selection filter  24  is located on the optical path of the blue laser light L 3 . The wavelength selection filter  22  reflects the red laser light L 1  collimated by the lens  18  toward the wavelength selection filter  23 . The wavelength selection filter  23  transmits the red laser light L 1  and reflects the green laser light L 2  collimated by the lens  19  toward the wavelength selection filter  24 . The wavelength selection filter  24  transmits the red laser light L 1  and the green laser light L 2  and reflects the blue laser light L 3  collimated by the lens  20 . Therefore, the laser lights L 1  to L 3  output from the LDs  14  to  16  are multiplexed by the multiplex optical system  21  having the wavelength selection filters  22  to  24 . 
     The lenses  18  to  20  and the wavelength selection filters  22  to  24  are respectively in a state in which the optical axes of the red laser light L 1 , the green laser light L 2 , and the blue laser light L 3  included in the laser light L are adjusted so as to coincide with each other. 
     The cap  4  shown in  FIG. 1  is a member for protecting the light source portion  3 , and is fixed to the primary face  2   a  of the base  2 . That is, the cap  4  is a member that is fixed to the base  2  and covers the carrier  13 , the LDs  14  to  16 , and the like. The cap  4  is, for example, welded to the base  2  (hermetic seal). A light source portion  3  and portions of each lead pin  5  protruding from the primary face  2   a  are accommodated in an interior space of the laser module  1  defined by the base  2  and the cap  4 . The cap  4  is provided with an opening  4   a  through which the laser light L passes. For example, glass or the like is airtightly fitted into the opening  4   a.    
     Next, the organic adhesive layer  31  will be described in detail with reference to  FIG. 4B .  FIG. 4B  is a schematic enlarged sectional view of a portion indicated by a broken line in  FIG. 4A . 
     The organic adhesive layer  31  is used for fixing the LD  14  to the carrier  13 , and is a layer having at least an organic substance-containing adhesive. The organic adhesive layer  31  is formed when the LD  14  is fixed to the carrier  13  via an organic substance-containing adhesive. The organic-containing adhesive is a curable adhesive containing at least one of a low molecular organic compound and a high molecular organic compound, and is applied onto, for example, the first portion  13   a  of the carrier  13  or the submount  14   a  of the LD  14 . The curable adhesive includes, for example, an ultraviolet curable resin, a thermosetting resin, or a mixture of an ultraviolet curable resin and a thermosetting resin. In the first embodiment, the organic compounds included in the organic adhesive layer  31  include at least one of Si and O. Therefore, the organic-containing adhesive includes, for example, siloxane. In the first embodiment, the organic-containing adhesive comprises at least a siloxane. The organic compound included in the organic adhesive layer  31  may volatilize due to heat generated by the operation of the LD  14  and the like, for example. 
     The organic adhesive layer  31  has an exposed portion  31   a  exposed from the carrier  13  and the LD  14 . The exposed portion  31   a  is a portion overflowing from between the carrier  13  and the LD  14  to the outside, and is located on the first portion  13   a . In a plan view, the exposed portion  31   a  overflows from a part or the whole of the LD  14  to the outside. In the first embodiment, the exposed portion  31   a  overflows from a whole of the LD  14  in a plan view. 
     The exposed portion  31   a  is covered by a cover material  32 . The cover material  32  is a film member that directly or indirectly covers the exposed portion  31   a . The cover material  32  has a single-layer structure or a multilayer structure and includes, for example, silicon oxide. In this case, the cover material  32  may include a single silicon oxide layer or may include multiple silicon oxide layers. At least one of Si and O forming the silicon oxide may be a part of Si and O included in the organic adhesive layer  31 . In the first embodiment, the cover material  32  has a layer shape covering at least a part of the carrier  13  in addition to the whole of the exposed portion  31   a . The cover material  32  is in contact with the submount  14   a  of the LD  14 . Therefore, in the first embodiment, the organic adhesive layer  31  including the exposed portion  31   a  is sealed by the carrier  13 , the LD  14 , and the cover material  32 . The silicon oxide is not limited to SiO 2  and may be a substance including Si and O as main components. 
     Next, with reference to a comparative example described below, the operation and effect achieved by the laser module  1  according to the first embodiment will be described. A laser module (not shown) according to the comparative example has the same configuration as the laser module  1  according to the first embodiment except that the cover material  32  described above is not formed. 
       FIG. 5  is a schematic cross-sectional view showing a laser light emitting end face of an LD of a laser module according to the comparative example. As shown in  FIG. 5 , the laser light emitting end face of the LD  114  according to the comparative example is formed by a stack  115 . The stack  115  is provided to adjust the reflectance of the laser light emission end face, and includes, for example, a stack of dielectric layers. A silicon oxide film  116  is provided on the laser light emitting end face of the LD  114 . The silicon oxide film  116  is a deposit based on an organic compound volatilized at the interior space of the package. Thus, the silicon oxide film  116  is more easily provided as the vapor pressure of the organic compound gas in the interior space is higher. In addition, the silicon oxide film  116  is deposited on the LD  114  with the use of the laser module (i.e., oscillation of the LD). The deposit based on the organic compound is likely to aggregate in the portion  114   a  where the laser oscillates in the LD  114 . This is because the constituent substance of the organic compound decomposed by the laser output from the LD  114  is likely to adhere to the portion  114   a  closest to the decomposition position of the organic compound. Therefore, the thickness of the silicon oxide film  116  is not uniform, and the portion overlapping the portion  114   a  is thickest. When a plurality of LDs are provided in a package, a deposit based on an organic compound is likely to be formed on an LD having a short wavelength and high energy. This is because an LD having a shorter wavelength and higher energy is more likely to decompose an organic compound. For example, an LD having an emission wavelength of 500 nm or less is likely to be deteriorated in characteristics due to the deposit. 
     When the silicon oxide film  116  is formed as in the comparative example, the optical path length of the LD  114  deviates from the design value. Therefore, in the laser module, the higher the vapor pressure of the organic compound gas on the interior space of the package, the more easily the laser characteristics of the LD  114  are degraded. 
     In contrast to the comparative example, in the laser module  1  according to the first embodiment, the exposed portion  31   a  of the organic adhesive layer  31  exposed from the carrier  13  and the LD  14  is covered with the cover material  32 . Moreover, in the first embodiment, the exposed portion  31   a  is sealed by the carrier  13 , the LD  14 , and the cover material  32 . Accordingly, the organic compound included in the organic adhesive layer  31  can be prevented from volatilizing into the interior space defined by the base  2  and the cap  4 . Therefore, the vapor pressure of the organic compound gas in the interior space can be reduced without limiting the component of the organic compound included in the organic adhesive layer  31 . Therefore, a deposit based on the organic compound gas is less likely to be formed on the laser light emitting end surface of the LD  14  and the like. In other words, it is possible to suppress a gap of the optical path length of the LD  14  and the like due to the use of the laser module  1 . Therefore, according to the laser module  1  of the first embodiment, it is possible to suppress the characteristic deterioration due to the gas of the organic compound without limiting the variety of the organic compound included in the organic adhesive layer  31 . 
     Moreover, with reference to  FIGS. 6A, 6B, and 7 , the reason why the above-described effects are obtained by using the laser module  1  will be described in detail.  FIG. 6A  is a graph showing an output variation accompanying the use of the laser module according to the comparative example, and  FIG. 6B  is a graph showing an output variation accompanying the use of the laser module according to the first embodiment. 
     In  FIGS. 6A and 6B , the horizontal axis represents time and the vertical axis represents the output of the laser module. In  FIGS. 6A and 6B , the initial output value of the laser module is  1 .  FIG. 6A  shows data  41 ,  42 ,  43 , and  FIG. 6B  shows data  44 ,  45 ,  46 . Data  41  to  43  show the output variation results of the laser modules according to the comparative examples manufactured under the same conditions. Data  44  to  46  show the output variation results of the laser modules  1  manufactured under the same conditions. As shown in  FIGS. 6A and 6B , in the comparative example, the output of the laser module decreases by 20% or more after about 700 hours. On the other hand, in the first embodiment, the output reduction of the laser module is less than 20% even after about 2000 hours. From the above results, it can be seen that the output reduction rate associated with the use of the laser module is improved by covering the organic adhesive layer  31  with the cover material  32 . 
       FIG. 7  is a view showing the results of measuring the carrier surfaces of the laser modules according to the comparative example and the first embodiment by TOF-SIMS. In the TOF-SIMS, an analyzer “PHI nanoTOF II (registered trademark)” manufactured by ULVAC-PHI, Inc. was used. The measurement conditions of TOF-SIMS were a raster size of 500 μm square, a first ion species of Bi 3+ , and a first ion acceleration voltage of 30 kV. In  FIG. 7 , the vertical axis represents the amount of detection of substance. In  FIG. 7 , the amount of detection of silicon oxide in the first embodiment is  1 . As shown in  FIG. 7 , in the comparative example, a large number of siloxanes were present on the carrier surface, while silicon oxide was hardly present. On the other hand, in the first embodiment, a large number of silicon oxides were present on the carrier surfaces, while siloxane was hardly present. From the above results, it can be seen that siloxane, which is the material of the silicon oxide film deposited on the laser light emitting end face of the LD, is less likely to exist inside the package by covering the organic adhesive layer  31  with the cover material  32 . In other words, a silicon oxide film based on siloxane included in the organic adhesive layer  31  is less likely to be formed on the laser light emitting end surface of the LD by covering the organic adhesive layer  31  with the cover material  32 . Therefore, from the results shown in  FIGS. 6A and 6B  and  FIG. 7  as well, it can be seen that, according to the laser module  1  of the first embodiment, it is possible to suppress the characteristic deterioration due to the gas of the organic compound without limiting the variety of the organic compound included in the organic adhesive layer  31 . 
     In the first embodiment, the cover material  32  also covers at least a part of the carrier  13 . In this case, since the cover material  32  is less likely to be peeled off, the function of preventing volatilization of the organic compound gas obtained by the cover material  32  can be maintained for a long time. In addition, since volatilization of the organic compound attached to the surface of the carrier  13  can be suppressed, the vapor pressure of the organic compound gas on the interior space of the package can be favorably reduced. In addition, the cover material  32  may cover a part of the LD  14  in addition to the carrier  13 . In this case, the cover material  32  is more difficult to peel off. Furthermore, since the volatilization of the organic compound attached to the surface of the LD  14  can be suppressed, the vapor pressure of the organic compound gas in the interior space of the package can be more favorably reduced. 
     In the first embodiment, the cover material  32  covers the whole of the exposed portion  31   a  of the organic adhesive layer  31 . Therefore, the organic compound gas is less likely to volatilize. That is, according to the first embodiment, the characteristic deterioration of the laser module  1  can be favorably suppressed. 
     In the first embodiment, cover material  32  may include silicon oxide. In this case, the organic adhesive layer  31  may include at least one of Si and O, and the silicon oxide may include at least one of Si and O. In this case, since the silicon oxide included in the cover material  32  can have a dense molecular structure, volatilization of the organic compound gas from the organic adhesive layer  31  can be favorably suppressed. In other words, it is possible to improve the function of preventing volatilization of the organic compound gas obtained by the cover material  32 . 
     Next, modifications of the first embodiment will be described with reference to  FIGS. 8A and 8B . Hereinafter, only configurations different from those of the above-described embodiment will be described, and descriptions of configurations identical to those of the above-described first embodiment will be omitted. 
       FIG. 8A  is an enlarged cross-sectional view of a main part of a laser module according to a first modification. As shown in  FIG. 8A , the submount  14   a  of the LD  14  is fixed on the first portion  13   a  of the carrier  13  via an organic adhesive layer  31 A. In the first modification, the organic adhesive layer  31 A does not overflow from the LD  14  in a plan view. Therefore, the organic adhesive layer  31 A according to the first modification has an exposed face  31   b  which is an exposed portion exposed from the carrier  13  and the LD  14 . The exposed face  31   b  is covered with a cover material  32 A. The cover material  32 A is provided in the space between the carrier  13  and the LD  14 , and is in contact with the exposed face  31   b . An organic adhesive layer  31 A is provided in a space sealed by the cover material  32 A, the carrier  13 , and the LD  14 . Even in such a first modification, the same operational effects as those of the first embodiment described above are exhibited. 
       FIG. 8B  is an enlarged cross-sectional view of a main part of a laser module according to a second modification. As shown in  FIG. 8B , unlike the cover material  32 A of the first modification, the cover material  32 B is spaced apart from the exposed face  31   b  and indirectly covers the organic adhesive layer  31 A. In the second modification, the organic adhesive layer  31 A is provided in the space sealed by the cover material  32 B, the carrier  13 , and the LD  14 . Even in such a second modification, the same operational effects as those of the first embodiment described above are exhibited. 
     Second Embodiment 
     Hereinafter, the laser module according to the second embodiment will be described. In the description of the second embodiment, description overlapping with the first embodiment will be omitted, and portions different from the first embodiment will be described. That is, the description of the first embodiment may be appropriately applied to the second embodiment within a technically possible range. 
       FIG. 9A  is an enlarged cross-sectional view of a main part of the laser module according to the second embodiment. In the second embodiment, an organic adhesive layer is used to fix a lens, which is an optical element, and a carrier. In detail, as shown in  FIG. 9A , an organic adhesive layer  51  is provided between the second portion  13   b  of the carrier  13  and the holding resin  18   b  of the lens  18 . The organic adhesive layer  51  is made of the same material as the organic adhesive layer  31  and has an exposed portion  51   a . The exposed portion  51   a  is covered by a cover material  52 . The cover material  52  is a film member that directly or indirectly covers the exposed portion  51   a , and has the same configuration as the cover material  32 . The cover material  52  covers at least a part of the carrier  13  in addition to the whole of the exposed portion  51   a . The cover material  52  is in contact with the lens  18 . Therefore, in the second embodiment, the organic adhesive layer  51  including the exposed portion  51   a  is sealed by the carrier  13 , the lens  18 , and the cover material  52 . The cover material  52  may be formed at the same time as the cover material  32 , or may be formed at a different timing from the cover material  32 . The cover materials  32 ,  52  may be the same layer continuous with each other or may be layers independent of each other. 
     According to the laser module of the second embodiment, the same operation and effect as those of the first embodiment are achieved. In addition, volatilization of an organic compound in the interior space defined by the base  2  and the cap  4  can be favorably suppressed. In the second embodiment, an organic adhesive layer for fixing each of the lenses  19 ,  20  and the carrier  13  may be used. These organic adhesive layers are also covered with the cover material  52  such that volatilization of the organic compound into the interior space can be favorably suppressed. 
       FIG. 9B  is an enlarged cross-sectional view of a main part of a laser module according to a modification of the second embodiment. As shown in  FIG. 9B , an organic adhesive layer  53  is provided between the wavelength selection filter  22  which is an optical element and the second portion  13   b  of the carrier  13 . The organic adhesive layer  53  is made of the same material as the organic adhesive layer  31  similarly to the organic adhesive layer  51 , and has an exposed portion  53   a . The exposed portion  53   a  is covered by a cover material  54 . Specifically, the organic adhesive layer  53  including the exposed portion  53   a  is sealed by the carrier  13 , the wavelength selection filter  22 , and the cover material  54 . Even in such a modification, the same operation and effect as those of the second embodiment can be achieved. In this modification, an organic adhesive layer for fixing each of the wavelength selection filters  23 ,  24  and the carrier  13  may be used. 
     These organic adhesive layers are also covered with the cover material  54 , so that volatilization of organic compounds into the interior space can be favorably suppressed. The cover material corresponding to each organic adhesive layer may be a single layer or different layers. 
     Third Embodiment 
     Hereinafter, the laser module according to the third embodiment will be described. In the description of the third embodiment, the description overlapping with the first and second embodiments will be omitted, and portions different from the first and second embodiments will be described. That is, the descriptions of the first and second embodiments may be appropriately applied to the third embodiment within a technically possible range. 
       FIG. 10A  is a perspective view illustrating a state in which a cap is removed from the laser module according to the third embodiment.  FIG. 10B  is an enlarged cross-sectional view of a main part of  FIG. 10A . As shown in  FIG. 10A , in the third embodiment, unlike the first embodiment, the TEC is not fixed to the base  2 . As shown in  FIG. 10B , the carrier  13 A and the base  2  are fixed by an organic adhesive layer  61 . The organic adhesive layer  61  is made of the same material as the organic adhesive layer  31  and has an exposed portion  61   a . The exposed portion  61   a  is covered by a cover material  62 . The cover material  62  is a film member that directly or indirectly covers the exposed portion  61   a , and has the same configuration as the cover material  32 . The cover material  62  covers at least a part of the base  2  in addition to the whole of the exposed portion  61   a . The cover material  62  is in contact with the carrier  13 A. Therefore, in the third embodiment, the organic adhesive layer  61  including the exposed portion  61   a  is sealed by the base  2 , the carrier  13 A, and the cover material  62 . The cover material  62  may be formed at the same time as the cover material  32  or may be formed at a different timing from the cover material  32 . The cover materials  32 ,  62  and may be the same layer continuous with each other or may be layers independent of each other. 
     According to the laser module of the third embodiment, the same operation and effect as those of the first embodiment are achieved. In addition, volatilization of the organic compound in the interior space defined by the base  2  and the cap  4  can be favorably suppressed. According to the third embodiment, a temperature adjust element may be provided in the carrier  13 A. 
     Fourth Embodiment 
     Hereinafter, the laser module according to the fourth embodiment will be described. In the description of the fourth embodiment, description overlapping with the first to third embodiments is omitted, and portions different from the first to third embodiments are described. That is, the descriptions of the first to third embodiments may be appropriately used for the fourth embodiment within a technically possible range. 
       FIG. 11A  is a perspective view showing a laser module according to the fourth embodiment.  FIG. 11B  is a perspective view showing a state in which the cap is removed from the laser module of  FIG. 11A . The laser module  1 A shown in  FIGS. 11A and 11B  is a so-called CAN package type device. The laser module  1 A includes a base  2 A, a light source portion  3 A, and a cap  4 A. The base  2 A includes a main portion  6   a  having a substantially disk shape and a protrusion  6   b  protruding from the main portion  6   a . The main portion  6   a  is provided with a plurality of lead pins  5 A. Protrusion  6   b  protrudes along a direction opposite to the direction in which lead pin  5 A extends. The cap  4 A includes a cover  7   a  having a substantially cylindrical shape and a cover glass  7   b  that seals one end side of the cover  7   a . The other end of the cover  7   a  is attached to the main portion  6   a  of the base  2 A. Protrusion  6   b  is sealed by main portion  6   a  and cap  4 A. 
     The light source portion  3 A includes a carrier  13 B that functions as a submount mounted on the base  2 A and an LD  71  mounted on the carrier  13 B. The carrier  13 B is fixed to the protrusion  6   b  via an adhesive. In the fourth embodiment, an organic adhesive layer (not shown) is used to fix the base  2 A and the carrier  13 B. Moreover, in the organic adhesive layer, an exposed portion exposed between the base  2 A and the carrier  13 B is covered by a cover material. The cover material is a film member that directly or indirectly covers the exposed portion, and has the same configuration as the cover material  32 . The cover material covering the exposed portion exposed from the base  2 A and the carrier  13 B covers at least a part of the base  2 A in addition to whole of the exposed portion. The cover material is in contact with the carrier  13 B. Therefore, in the fourth embodiment, the organic adhesive layer including the exposed portion is sealed by the base  2 A, the carrier  13 B, and the cover material. 
     The LD  71  has an emission wavelength of 500 nm or less and is fixed to the carrier  13 B via an adhesive. In the fourth embodiment, an organic adhesive layer (not shown) is used to fix the carrier  13 B and the LD  71 . Moreover, in the organic adhesive layer, an exposed portion exposed between the carrier  13 B and the LD  71  is covered with a cover material. The cover material is a film member that directly or indirectly covers the exposed portion, and has the same configuration as the cover material  32 . The cover material covering the exposed portion exposed from the carrier  13 B and the LD  71  covers at least a part of the carrier  13 B in addition to whole of the exposed portion. The cover material is in contact with the LD  71 . Therefore, in the fourth embodiment, the organic adhesive layer including the exposed portion is sealed by the carrier  13 B, the LD  71 , and the cover material. 
     The cover material covering the exposed portion exposed from the base  2 A and the carrier  13 B and the cover material covering the exposed portion exposed from the carrier  13 B and the LD  71  may be formed at the same time or at different timings. These cover materials may be the same layer continuous with each other or may be layers independent of each other. 
     According to the laser module of the fourth embodiment, the same operation and effect as those of the first embodiment are achieved. In addition, volatilization of the organic compound into the interior space defined by the base  2 A and the cap  4 A can be favorably suppressed. 
     The laser module according to the present disclosure is not limited to the above-described embodiments and modifications, and various other modifications are possible. The above-described embodiment and the above-described modifications may be appropriately combined. For example, the aspect of the first modification or the second modification of the first embodiment may be applied to the second to fourth embodiments, or the first embodiment and the second embodiment may be combined. In a case where the above-described embodiment and the above-described modifications are appropriately combined, the laser module may be provided with a cover material that is a single layer or may be provided with a plurality of layered cover materials. 
     In the first embodiment and the first and second modifications, the organic adhesive layer is sealed by the cover material, the carrier, and the LD, but the present disclosure is not limited to this. A part of the organic adhesive layer may be exposed from the cover material, the carrier, and the LD. Even in this case, it is possible to suppress the characteristic deterioration due to the gas of the organic compound as compared with the comparative example in which the cover material is not provided. Similarly, in the second to fourth embodiments and the like, a part of the organic adhesive layer may be exposed from the cover material. 
     In the above-described embodiments and the above-described modifications, the cover material is a single film-like member, but is not limited to this aspect. For example, the cover material may be a plurality of members separated from each other, or may be a film-like member provided with holes or the like. 
     In the first embodiment and the modifications, the cover material covers the exposed portion of the organic adhesive layer that fixes the carrier and the LD, but the present disclosure is not limited to this. For example, in the above-described embodiment and the above-described modifications, the cover material may cover an adhesive layer other than the organic adhesive layer that fixes the LD that emits red laser light and the carrier. As a specific example, an exposed portion of the adhesive layer fixing the LD emitting the green laser light and the carrier and an exposed portion of the adhesive layer fixing the LD emitting the blue laser light and the carrier may be covered with a cover material. In this case, a single cover material may cover all exposed portions. Alternatively, a plurality of cover materials may be used. 
     For example, the cover material may cover an exposed portion of the adhesive layer located inside the package. As a specific example, the cover material may function to cover an exposed portion of an adhesive layer used to secure the TEC and the base. In this case, the cover material covering the exposed portion of the organic adhesive layer and the cover material covering the exposed portion of the adhesive layer may be integrated with each other or may be separated from each other. The cover material may cover an exposed portion of the adhesive layer used to fix the carrier and the thermistor. 
     In the above first to third embodiments and the above modifications, the laser module includes three LDs, but the number of LDs of the laser module is not limited to three. The laser module may include one or two LDs, or may include four or more LDs. Even in the above case, when the laser module includes an LD having an emission wavelength of 500 nm or less, the deterioration of the characteristics of the LD can be favorably suppressed. On the other hand, in the fourth embodiment, one LD is mounted on the carrier, but a plurality of LDs may be mounted on a plurality of carriers. 
     In the above-described embodiment and the above-described modification, a device other than the light source portion may be accommodated in the package of the laser module. For example, a MEMS, a photodiode (PD), and the like may be accommodated in a package. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
           1 , 1 A laser module 
           2 ,  2 A base 
           2   a  primary face 
           3 ,  3 A light source portion 
           4 ,  4 A cap 
           4   a  opening 
           5 ,  5 A lead pin 
           6   a  main portion 
           6   b  protrusion 
           7   a  cover 
           7   b  cover glass 
           11  TEC 
           12   a ,  12   b  substrate 
           12   c  thermoelectric element 
           13 ,  13 A,  13 B carrier 
           13   a  first portion 
           13   b  second portion 
           14 ,  15 ,  16 ,  71 ,  114  laser diode (LD) 
           14   a ,  15   a ,  16   a  submount 
           14   b ,  15   b ,  16   b  laser oscillator 
           17  thermistor 
           18 ,  19 ,  20  lens 
           18   a ,  19   a ,  20   a  lens function region 
           18   b ,  19   b ,  20   b  holding region 
           21  multiplex optical system 
           22 ,  23 ,  24  wavelength selection filter 
           31 ,  31 A,  51 ,  53 ,  61  organic adhesive layer 
           31   a ,  51   a ,  53   a ,  61   a  exposed portion 
           31   b  exposed face 
           32 ,  32 A,  32 B,  52 ,  54 ,  62  cover material 
           41 ,  42 ,  43 ,  44 ,  45 ,  46  data 
           114   a  portion 
           115  stack 
           116  silicon oxide film 
         L laser light 
         L 1 . red laser light 
         L 2  green laser light 
         L 3  Blue laser light.