Patent Publication Number: US-2023160744-A1

Title: Light-emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-191589, filed on Nov. 25, 2021, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a light-emitting device. 
     Japanese Patent Publication No. 2021-93514 discloses a light source device including a light-emitting element, an optical member that reflects a part of light emitted from the light-emitting element and transmits the remaining light, and a photodetector that receives the light transmitted through the optical member. Furthermore, the light source device disclosed in the Japanese Patent Publication No. 2021-93514 has an object to monitor an output of laser light with high accuracy and provides a slit as one solution related to the object. 
     SUMMARY 
     In a manufacturing process of a light-emitting device, the occurrence of trouble such as poor bonding is preferably suppressed. There is room for considering the improvement in order to provide a light-emitting device having stable quality. 
     In an exemplary and non-limiting embodiment, a light-emitting device according to the present disclosure includes a plurality of light-emitting elements, a photodetector, an optical member and a bonding portion. The plurality of light-emitting elements include a first light-emitting element configured to emit first light and a second light-emitting element configured to emit second light. The photodetector is configured to receive a part of light emitted from each of the plurality of light-emitting elements. The photodetector has a first bonding surface. The optical member has a second bonding surface and a first inner side surface. The second bonding surface is bonded to the first bonding surface of the photodetector. The first inner side surface is continuous from the second bonding surface. The light emitted from each of the plurality of light-emitting elements is configured to pass through the optical member. The bonding portion bonds the photodetector and the optical member with the bonding portion being in contact with the first bonding surface, the second bonding surface, and at least a part of the first inner side surface. 
     Embodiments of the present disclosure can provide a light-emitting device having stable quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a light-emitting device according to a first embodiment of the present disclosure. 
         FIG.  2    is a perspective view of the light-emitting device according to the first embodiment of the present disclosure excluding a second cap and a lid member. 
         FIG.  3    is a cross-sectional view taken along a section line in  FIG.  2   . 
         FIG.  4    is a perspective view of the light-emitting device according to the first embodiment of the present disclosure excluding a first cap, the second cap, and the lid member. 
         FIG.  5    is a top view corresponding to the perspective view illustrated in  FIG.  4   . 
         FIG.  6    is a top view illustrating wiring lines inside a package. 
         FIG.  7 A  is a top view of an optical member and a photodetector according to the first embodiment. 
         FIG.  7 B  is a cross-sectional view of the optical member and the photodetector taken along a section line VIIB-VIIB in  FIG.  7 A . 
         FIG.  8 A  is a top view of an optical member and a photodetector according to a second embodiment. 
         FIG.  8 B  is a cross-sectional view of the optical member and the photodetector taken along a section line in  FIG.  8 A . 
         FIG.  9 A  is a top view of an optical member and a photodetector according to a third embodiment. 
         FIG.  9 B  is a cross-sectional view of the optical member and the photodetector taken along a section line IXB-IXB in  FIG.  9 A . 
         FIG.  10 A  is a top view of an optical member and a photodetector according to a fourth embodiment. 
         FIG.  10 B  is a cross-sectional view of the optical member and the photodetector taken along a section line XB-XB in  FIG.  10 A . 
         FIG.  11    is a side view schematically illustrating a configuration example of a head-mounted display according to the embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the present description or the scope of the claims, a polygon such as a triangle and a quadrangle is not limited to a polygon in a mathematically strict sense and also includes a shape in which a corner of the polygon is processed to be rounded, chamfered, beveled, coved, and the like. Furthermore, a shape obtained by processing not only the corner (an end of a side) of the polygon, but also a middle portion of the side is similarly referred to as a polygon. In other words, a shape partially processed while leaving the polygon as a base is included in the “polygon” described in the present description and the scope of the claims. 
     The same applies not only to the polygon but also to a word representing a specific shape such as a trapezoid, a circle, a protrusion, and a recession. The same applies when dealing with each side forming that shape. In other words, even when a corner and a middle portion of a certain side are processed, the “side” also includes the processed portion. When the “polygon” or “side” not partially processed is to be distinguished from a processed shape, “strict” will be added to the description as in, for example, a “strict quadrangle”. 
     In the present description or the scope of the claims, when there are a plurality of components identified by a certain term and each of the components is to be expressed separately, an ordinal number such as “first” and “second” may be added in front of each of the terms of the components. For example, when it is described that “light-emitting elements are disposed on a substrate” in the claims, it may be described that “a first light-emitting element and a second light-emitting element are arrayed on a substrate” in the description. The ordinal numbers of “first” and “second” are used to distinguish the two light-emitting elements. A term of a component provided with the same ordinal number may not refer to the same component between the description and the claims. For example, when components identified by terms of a “first light-emitting element”, a “second light-emitting element”, and a “third light-emitting element” are described in the description, a “first light-emitting element” and a “second light-emitting element” in the claims may correspond to the “first light-emitting element” and the “third light-emitting element” in the description. Furthermore, in claim  1  described in the claims, when the term of the “first light-emitting element” is used and the term of the “second light-emitting element” is not used, the invention according to claim  1  includes one light-emitting element. The light-emitting element is not limited to the “first light-emitting element” in the description, and can be the “second light-emitting element” or the “third light-emitting element”. 
     In the present description or the scope of the claims, terms indicating a specific direction or position (for example, “upper”, “lower”, “right”, “left”, “front”, and “rear”) may be used. The terms are merely used to make it easy to understand a relative direction or position in the referenced drawing. As long as the relative direction or position is the same as that described in the referenced drawing using the term such as “upper” or “lower”, in drawings other than the drawings of the present disclosure, actual products, manufacturing devices, and the like, components need not necessarily be arranged in the same manner as in the referenced drawing. 
     A size, a size ratio, a shape, an arrangement interval, and the like of a component or a member illustrated in the drawings may be exaggerated for ease of understanding. Furthermore, in order to avoid excessive complication of the drawings, illustration of some elements may be omitted. 
     Embodiments of the present invention will be described below with reference to the drawings. The embodiments are for embodying the technical concept of the present invention but are not intended to limit the present invention. A numerical value, a shape, a material, and the like indicated in the description of the embodiments are merely one example, and various modifications can be made as long as a technical contradiction does not arise. In the following description, a component identified by the same term and reference sign is the same component or a similar component, and duplicate descriptions of the components may be omitted. 
     First Embodiment 
     A schematic structure of a light-emitting device according to a first embodiment will be described with reference to the drawings.  FIGS.  1  to  7 B  are drawings for illustrating an exemplary embodiment of a light-emitting device  200 . In the accompanying drawings, an X-axis, a Y-axis, and a Z-axis orthogonal to each other are indicated for reference. 
       FIG.  1    is a perspective view of the light-emitting device  200 .  FIG.  2    is a perspective view of the light-emitting device  200  excluding a second cap  120  and a lid member  130 .  FIG.  3    is a cross-sectional view taken along a section line in  FIG.  2   . In  FIG.  3   , light traveling on an optical axis among light emitted from a light-emitting element  20  is indicated by a dotted line.  FIG.  4    is a perspective view of the light-emitting device  200  excluding a first cap  16  and the second cap  120 .  FIG.  5    is a top view corresponding to the perspective view illustrated in  FIG.  4   . In  FIG.  5   , light traveling on the optical axis among light emitted from each of three light-emitting elements  20  is indicated by a dot-dash line.  FIG.  6    is a top view illustrating wiring lines inside a package  10 .  FIG.  7 A  is a top view of an optical member and a photodetector according to the first embodiment.  FIG.  7 B  is a cross-sectional view of the optical member and the photodetector taken along a section line VIIB-VIIB in  FIG.  7 A . 
     The light-emitting device  200  according to the present embodiment includes a substrate  11 , the first cap  16  (see  FIG.  3   ), and the plurality of light-emitting elements  20 . The light-emitting device  200  in the illustrated by drawings further includes a submount  30 , an optical member  40 A, a photodetector  50 , one or a plurality of protective elements  60 A, a temperature measuring element  60 B, one or a plurality of lens members  80 , a beam combiner  90 , the second cap  120 , and the lid member  130 . However, these components are not essential. The plurality of light-emitting elements  20  are configured to include a first light-emitting element  20   a  and a second light-emitting element  20   b . Furthermore, the plurality of light-emitting elements  20  can be configured to further include a third light-emitting element  20   c . The plurality of light-emitting elements  20  may include two or more light-emitting elements  20  having an equal emission peak wavelength. 
     In the light-emitting device  200  in the illustrated by the drawings, the plurality of light-emitting elements  20 , the submount  30 , the optical member  40 A, the photodetector  50 , the plurality of protective elements  60 A, and the temperature measuring element  60 B are disposed in a space defined by the substrate  11  and the first cap  16 . Further, the lens member  80  and the beam combiner  90  are disposed outside the space. 
     The light-emitting device  200  in the present embodiment has a substantially box shape. A size in an X direction can be, for example, equal to or less than 10 mm, and a size in a Z direction can be, for example, equal to or less than 15 mm. A height in a Y direction can be, for example, equal to or less than 4 mm. 
     First, each of the components will be described. 
     Substrate  11   
     The substrate  11  includes an upper surface and a lower surface facing the upper surface. The upper surface functions as a mounting surface  11 M on which one or more components included in the light-emitting device  200  are disposed. The mounting surface  11 M is a flat plane. The mounting surface  11 M includes a first mounting region  18   a  and a second mounting region  18   b . The first mounting region  18   a  and the second mounting region  18   b  are provided on the same flat plane. Note that the first mounting region  18   a  and the second mounting region  18   b  may not be provided on the same flat plane. For example, the substrate  11  may include flat planes having different heights, and the first mounting region  18   a  and the second mounting region  18   b  may be provided on the corresponding flat planes. 
     The substrate  11  can be formed of ceramic as a main material. Examples of the ceramic include aluminum nitride, silicon nitride, aluminum oxide, silicon carbide, and the like. The substrate  11  in the illustrated by the drawings has a flat plate shape. Note that the substrate  11  may not have the flat plate shape. 
     First Cap  16   
     The first cap  16  includes a side wall portion  12  and an upper portion  15 . The first cap  16  has a recessed shape. An outer shape of the first cap  16  is rectangular in a top view. However, the outer shape of the first cap  16  does not need to be rectangular, and may be, for example, polygonal other than quadrangular, circular, or the like. An internal space surrounded by the substrate  11 , the side wall portion  12 , and the upper portion  15  can be a sealed space. Furthermore, the internal space can be in an airtight state. 
     The side wall portion  12  surrounds the first mounting region  18   a  of the substrate  11  and extends above the mounting surface  11 M. One or more components disposed in the first mounting region  18   a  are surrounded by the side wall portion  12 . The side wall portion  12  does not surround the second mounting region  18   b  of the substrate  11 . One or more components disposed in the second mounting region  18   b  are not surrounded by the side wall portion  12 . The upper portion  15  is connected to the side wall portion  12  at a position above the mounting surface  11 M. The upper portion  15  is located directly above one or more components disposed in the first mounting region  18   a.    
     For example, the first cap  16  can be manufactured from a light-transmissive material such as glass, plastic, quartz, and sapphire by using a processing technique such as molding or etching. The first cap  16  may be formed by bonding the upper portion  15  and the side wall portion  12  that are individually formed by using different materials as main materials. For example, the main material of the upper portion  15  can be a non-light transmissive material such as monocrystalline silicon or polycrystalline silicone, and the main material of the side wall portion  12  can be a light-transmissive material such as glass. 
     In the illustrated by the drawings, the first cap  16  and the substrate  11  are collectively referred to as the package  10 . In the top view as seen along a normal direction of the mounting surface  11 M of the substrate  11 , that is, the illustrated Y direction, an outer shape of the package  10  is rectangular. The outer shape of the package  10  does not need to be rectangular, and may be, for example, polygonal other than quadrangular, circular, or the like. However, the “package” in the present embodiment is not limited thereto. In the present embodiment, the “package” can be a general structure including a “base portion” on which one or a plurality of members are disposed, and a “side wall portion” surrounding the one or the plurality of members. The “substrate  11 ” and the “side wall portion  12 ” in the illustrated by the drawings are one example of the “base portion” and the “side wall portion” of the package  10 , respectively. 
     Next, the package  10  in the illustrated by the drawings will be described. As illustrated in  FIG.  6   , the package  10  includes a plurality of wiring regions  14  for achieving electrical connection. The plurality of wiring regions  14  are provided in the first mounting region  18   a . Note that, in  FIG.  6   , instead of providing a reference sign to all of the plurality of wiring regions  14 , the same hatching is applied to each of the wiring regions  14 . The plurality of wiring regions  14  can be electrically connected to a wiring region provided on the lower surface of the substrate  11  (a surface opposite to the mounting surface  11 M) through a via hole passing through an inside of the substrate  11 . The wiring region electrically connected to the wiring region  14  is not limited to being provided on the lower surface of the substrate  11  and may be provided on another external surface (upper surface or outer side surface) of the package  10 . 
     As illustrated in  FIG.  3   , the package  10  includes a light incident surface  10 A and a light extraction surface  10 B that have light transmissivity on the side wall portion  12 . At least one surface of one or a plurality of outer side surfaces constituting the side wall portion  12  can be the light extraction surface  10 B. The light extraction surface  10 B can be perpendicular to the mounting surface  11 M. Note that the term “perpendicular” used here allows an error within ±5 degrees. The light extraction surface  10 B may be inclined to the mounting surface  11 M. 
     At least a part of a region of the light extraction surface  10 B has light transmissivity. The region having the light transmissivity is referred to as a light-transmissive region  13  (see  FIG.  3   ). Here, “having light transmissivity” means that a property in which a transmittance of main light incident thereon is equal to or more than 80% is satisfied. The light-transmissive region  13  may be located across the plurality of outer side surfaces of the package  10 . Further, the region having light transmissivity in the package  10  may not be limited to the light-transmissive region  13 . In the example of the illustrated package  10  illustrated by the drawings, the package  10  includes four outer side surfaces corresponding to the rectangular outer shape. All of the four outer side surfaces have light transmissivity. One surface of the four outer side surfaces is the light extraction surface  10 B. 
     The mounting surface  11 M of the substrate  11  further includes a peripheral region  11 P. The peripheral region  11 P surrounds the first mounting region  18   a . The peripheral region  11 P surrounds the first mounting region  18   a  and does not surround the second mounting region  18   b . The plurality of wiring regions  14  are surrounded by the peripheral region  11 P. The first cap  16  is bonded to the peripheral region  11 P of the substrate  11 . A metal film for bonding can be formed on the peripheral region  11 P. The plurality of wiring regions  14  can include a metal film that is formed of a conductor such as metal and is patterned. 
     Second Cap  120   
     In the example of the light-emitting device  200  illustrated by the drawings, the second cap  120  has a recessed shape. An outer shape of the second cap  120  is rectangular in the top view. In the top view as seen along the normal direction of the mounting surface  11 M of the substrate  11 , the second cap  120  includes the first cap  16 . The second cap  120  is fixed to the substrate  11 . The second cap  120  is bonded to a peripheral region along an outer edge of the mounting surface  11 M. An internal space of the second cap  120  is formed by bonding the second cap  120  to the substrate  11 . The internal space can be a sealed space. All of the one or the plurality of components disposed on the mounting surface  11 M of the substrate  11  can be accommodated in the internal space. 
     In the example of the second cap  120  illustrated by the drawings, an opening is provided in a side view as seen along the Z direction side. The second cap  120  can be formed of a light blocking material that blocks light. For example, the second cap  120  can be manufactured by molding a shape of the second cap  120  from glass and providing a light blocking film on a surface of the second cap  120 . 
     Lid Member  130   
     The lid member  130  has light transmissivity. The lid member  130  illustrated in  FIG.  1    has a flat plate shape. The lid member  130  is bonded to the substrate  11  and the second cap  120 . The lid member  130  covers the opening provided in the second cap  120 . The internal space formed of the second cap  120  can be a closed space by closing the opening of the second cap  120  with the lid member  130 . 
     Light-Emitting Element  20   
     Examples of the light-emitting element  20  include a semiconductor laser element (or a laser diode). The light-emitting element  20  can have an outer shape of the rectangle in the top view. When the light-emitting element  20  is an edge-emitting semiconductor laser element, a side surface intersecting one side of two short sides of the rectangle is an emission end surface. An upper surface and a lower surface of the light-emitting element  20  have an area greater than that of the emission end surface. The light-emitting element  20  is not limited to an edge-emitting semiconductor laser element and may be a surface-emitting semiconductor laser element such as a vertical cavity surface emitting laser (VCSEL), a light-emitting diode (LED), or the like. 
     The light-emitting element  20  in the present embodiment includes one or more light-emitting points on the emission end surface. The light-emitting element  20  may be a single emitter including one light-emitting point on the emission end surface or may be a multi-emitter including two or more light-emitting points on the emission end surface. The example of the light-emitting element  20  illustrated by the drawings is the single emitter. 
     Here, a description of a case in which the light-emitting element  20  is an edge-emitting semiconductor laser element is supplemented. Light (laser light) emitted from the emission end surface of the semiconductor laser element is divergent light that spreads. The laser light forms a far field pattern (hereinafter referred to as an “FFP”) of an elliptical shape on a plane parallel to the emission end surface. The FFP indicates a shape and a light intensity distribution of the emitted light at a position spaced apart from the emission end surface. 
     Light passing through the center of the elliptical shape of the FFP, in other words, light having a peak intensity in the light intensity distribution of the FFP, is referred to as light traveling on an optical axis. An optical path of the light traveling on the optical axis is referred to as the optical axis of the light. In the present embodiment, based on the light intensity distribution of the FFP, light having an intensity of 1/e 2  or more with respect to a peak intensity value is referred to as the light of a “main portion”. Note that, based on the light intensity distribution of the FFP, light having an intensity of half or more of the peak intensity value may be referred to as the light of the “main portion”. Note that, in  FIG.  5   , the light of the main portion emitted from the emission end surface of each of the light-emitting elements  20   a ,  20   b , and  20   c  is indicated by a dashed line. 
     In the elliptical shape of the FFP of the light emitted from the light-emitting element  20  being a semiconductor laser element, a minor axis direction of the elliptical shape is referred to as a slow axis direction, and a major axis direction is referred to as a fast axis direction. A plurality of layers including an active layer constituting the semiconductor laser element can be layered in the fast axis direction. 
     Based on the light intensity distribution of the FFP, an angle corresponding to 1/e 2  of the light intensity distribution is a spread angle of light of the semiconductor laser element. The spread angle of light in the fast axis direction is referred to as a fast-axis spread angle, and the spread angle of light in the slow axis direction is referred to as a slow-axis spread angle. The spread angle in the slow axis direction emitted from the semiconductor laser element can be equal to or more than 3°. 
     As the light-emitting element  20 , for example, a semiconductor laser element that emits red light, a semiconductor laser element that emits green light, a semiconductor laser element that emits blue light, or the like can be employed. Note that the light-emitting element  20  may emit light other than red light, green light, and blue light. Further, the light-emitting element  20  may emit light other than visible light. 
     Blue light refers to light having an emission peak wavelength within a range from 420 nm to 494 nm. Green light refers to light having the emission peak wavelength within a range from 495 nm to 570 nm. Red light refers to light having the emission peak wavelength within a range from 605 nm to 750 nm. 
     Examples of the semiconductor laser element that emits blue light or the semiconductor laser element that emits green light include a semiconductor laser element including a nitride semiconductor. GaN, InGaN, and AlGaN, for example, can be used as the nitride semiconductor. Examples of the semiconductor laser element that emits red light include a semiconductor laser element including an InAlGaP-based, GaInP-based, GaAs-based, or AlGaAs-based semiconductor. 
     Submount  30   
     As illustrated in  FIG.  3   , the submount  30  can include an upper surface  30 M and a lower surface located opposite to the upper surface  30 M and can have a rectangular parallelepiped shape. The upper surface  30 M and the lower surface each function as a bonding surface. A distance between the upper surface  30 M and the lower surface is shorter than distances between other two facing surfaces. A shape of the submount  30  may not limited to a rectangular parallelepiped. The submount  30  can be formed of, for example, silicon nitride, aluminum nitride, or silicon carbide. The submount  30  may include a metal film for bonding. The metal film for bonding is provided on each of the upper surface  30 M and the lower surface. One or a plurality of wiring regions electrically connected to other components can be provided on the upper surface  30 M. 
     Optical Member  40 A 
     The optical member  40 A includes a light incident surface and a light emission surface. The light emission surface is a surface opposite to the light incident surface. Further, the optical member  40 A includes a partial reflective surface (for example, the partial reflective surface R in  FIG.  3   ). The partial reflective surface reflects a part of light incident to the light incident surface and transmits the remaining light. 
     The partial reflective surface serves as a beam splitter. The light incident on the partial reflective surface is divided into two lights traveling in different directions. The two divided lights include light having the same wavelength. The optical member  40 A divides the same wavelength component of the incident light into two at a predetermined ratio. For example, one of the two lights divided by the optical member  40 A can be used as primary light (hereinafter referred to as “main light”), and the other of the two lights can be used as light (hereinafter referred to as “monitor light”) for monitoring to control the main light. 
     The optical member  40 A can be a rectangular parallelepiped as illustrated in  FIGS.  3  and  4   . The optical member  40 A includes an upper surface  43 , a lower surface  44 , and a plurality of outer side surfaces. Further, as illustrated in  FIG.  7 B , the optical member  40 A includes one or a plurality of recessed portions  110 . The optical member  40 A can include the plurality of recessed portions  110  including a first recessed portion  110   a  and a second recessed portion  110   b.    
     The recessed portion  110  includes one or a plurality of inner side surfaces  111 . The inner side surface  111  is continuous from the lower surface  44 . In other words, the lower surface  44  and the inner side surface  111  intersect each other. The recessed portion  110  can include the plurality of inner side surfaces  111  including an inner side surface  111   a  and an inner side surface  111   b  facing each other. 
     The recessed portion  110  further includes a lower surface  113  intersecting the inner side surface  111 . The lower surface  113  is continuous from the inner side surface  111 . The lower surface  113  intersects an upper side of the inner side surface  111 . The lower surface  113  can also be referred to as a connection surface that connects to the inner side surface  111   a  and the inner side surface  111   b  facing each other. In the recessed portion  110 , a recessed shape is defined by the inner side surface  111   a , the inner side surface  111   b , and the lower surface  113 . 
     Here, regarding the inner side surface and the lower surface included in the recessed portion  110 , for a distinction, an inner side surface and a lower surface included in the first recessed portion  110   a  are referred to as a first inner side surface and a first lower surface, respectively, and an inner side surface and a lower surface included in the second recessed portion  110   b  are referred to as a second inner side surface and a second lower surface, respectively. In  FIGS.  7 A and  7 B , two inner side surfaces  111  and the lower surface  113  included in the first recessed portion  110   a  are indicated by the first inner side surface  111   a , the first inner side surface  111   b , and a first lower surface  113   a , and two inner side surfaces  111  and the lower surface  113  included in the second recessed portion  110   b  are indicated by a second inner side surface  111   c , a second inner side surface  111   d , and a second lower surface  113   b.    
     A space (hereinafter referred to as a first space) from the lower surface  44  to the lower surface  113   a  is formed in the first recessed portion  110 , which has an opening at the lower surface  44 . The first space can be a space demarcated by the first inner side surface  111   a , the first inner side surface  111   b , the first lower surface  113   a , a flat plane including the lower surface  44 , a flat plane including the light incident surface, and a flat plane including the light emission surface. 
     A space (hereinafter referred to as a second space) from the lower surface  44  to the lower surface  113   b  is formed in the second recessed portion  110   b , which has an opening at the lower surface  44 . The second space can be a space demarcated by the second inner side surface  111   c , the second inner side surface  111   d , the second lower surface  113   b , the flat plane including the lower surface  44 , the flat plane including the light incident surface, and the flat plane including the light emission surface. 
     The recessed portion  110  can be formed in a slit shape. The recessed portion  110  is formed in a slit shape including a plurality of inner side surfaces in parallel with a Z-axis direction from a bonding surface  42 . The recessed portion  110  can be formed by a slit extending in the Z-axis direction. The inner side surface  111  extends in the optical member  40 A between the flat plane including the light incident surface and the flat plane including the light emission surface. The recessed portion  110  can be formed by a method such as cutting, with a blade, a region in which the recessed portion  110  is desired to be formed. 
     A height h2 (a maximum height) from the lower surface  44  of the optical member  40 A to a highest point of the lower surfaces  113   a  and  113   b  of the optical member  40 A is in a range from 5% to 90% of a height h1 (height from the lower surface  44  to the upper surface  43 ) of the optical member  40 A in a direction perpendicular to the bonding surface  42 . Furthermore, the height h2 is preferably in a range from 20% to 70% of the height h1. By setting the height h2 to be equal to or more than 20% of the height h1, the space demarcated by the recessed portion  110  can be ensured with a margin. By setting the height h2 to be equal to or less than 70% of the height h1, breakage of the optical member  40 A and a crack in the optical member  40 A can be suppressed. 
     The height h1 can be in a range from 0.2 mm to 2.0 mm. Furthermore, the height h1 is preferably in a range from 0.3 mm to 1.0 mm. By setting the height h1 to be equal to or more than 0.3 mm, the light incident surface and the light emission surface can be ensured with a margin. By setting the height h1 to be equal to or less than 1.0 mm, a size of the optical member  40 A can be suppressed. A width w1 of the optical member  40 A in the X direction can be in a range from 0.7 mm to 5.0 mm. The height h2 from the lower surface  44  of the optical member  40 A to the lower surface  113  can be in a range from 0.01 mm to 0.5 mm. A maximum width w2 of the recessed portion  110  in the X direction can be in a range from 0.05 mm to 0.5 mm. In the optical member  40 A illustrated by the drawings, for example, the height h1 can be 0.5 mm, the width w1 can be 5 mm, the height h2 can be 0.2 mm, and the width w2 can be 0.15 mm. 
     The lower surface  44  of the optical member  40 A includes a plurality of regions  41  spaced apart from each other on the flat plane including this lower surface  44 . The plurality of regions  41  include a first region  41   a  and a second region  41   b . Furthermore, the plurality of regions  41  can include a third region  41   c . The width w2 of the recessed portion  110  is less than a width of the region  41  in the X direction. 
     In a plan view as seen along a direction perpendicular to the lower surface  44  of the optical member  40 A, the inner side surface  111   a  is located between the first region  41   a  and the second region  41   b . In this plan view, the inner side surface  111   b  is located between the first region  41   a  and the second region  41   b . In this plan view, the inner side surface  111   c  is located between the second region  41   b  and the third region  41   c . In this plan view, the inner side surface  111   d  is located between the second region  41   b  and the third region  41   c . The direction perpendicular to the lower surface  44  of the optical member  40 A is the same direction as a Y-axis direction. 
     In the top view, the optical member  40 A can include a symbol surface extending in a long side direction. The symbol surface intersects the upper surface  43  and the outer side surface of the optical member  40 A. The symbol surface can be an inclined surface inclined relative to the upper surface  43 . The symbol surface can be used as a symbol for confirming an orientation of the optical member  40 A when viewed in the top view. In this way, an orientation of the optical member  40 A can be easily determined, and ease in mounting can be improved. 
     When the incident light is divided into the main light and the monitor light, intensity of the monitor light is less than intensity of the main light. For example, the partial reflective surface transmits in a range from 80% to 99.5% of incident light and reflects in a range from 0.5% to 20.0% of the incident light. 
     Photodetector  50   
     As illustrated in  FIG.  7 B , the photodetector  50  includes a lower surface  51 , a light receiving surface  52 , and a plurality of side surfaces  55 . The light receiving surface  52  is located opposite to the lower surface  51 . An outer shape of the photodetector  50  is a rectangular parallelepiped. Note that the outer shape may be different from the rectangular parallelepiped. 
     An outer shape of the light receiving surface  52  is rectangular. Note that the outer shape of the light receiving surface  52  may not be rectangular. A length of the light receiving surface  52  in the X direction is greater than a length of the light receiving surface  52  in the Z direction. A long side direction of the outer shape of the light receiving surface  52  is the same direction as the X direction, and a short side direction of the outer shape of the light receiving surface  52  is the same direction as the Z direction. 
     A plurality of light receiving regions  53  are provided on the light receiving surface  52 . The plurality of light receiving regions  53  include a first light receiving region  53   a  and a second light receiving region  53   b . Furthermore, the plurality of light receiving regions  53  can further include a third light receiving region  53   c . The light receiving region  53  can be provided in a one-to-one relationship with the light-emitting element  20 . 
     The plurality of light receiving regions  53  are spaced apart from each other in the light receiving surface  52 . The plurality of light receiving regions  53  are aligned along a first direction. The plurality of light receiving regions  53  are disposed side by side at a predetermined interval. The first direction is the same direction as the X direction. Examples of the photodetector  50  including the light receiving surface  52  include a photoelectric conversion element (photodiode) that outputs an electrical signal in accordance with an intensity or the amount of incident light. 
     The photodetector  50  includes a plurality of wiring patterns  54 . The plurality of wiring patterns  54  can be provided on the light receiving surface  52 . Note that the plurality of wiring patterns  54  may be provided on a surface other than the light receiving surface  52 , for example, on the side surface  55 . The wiring pattern  54  is electrically connected to the light receiving region  53 . The plurality of light receiving regions  53  are electrically connected to different wiring patterns  54 . 
     Protective Element  60 A 
     The protective element  60 A is a circuit element for preventing breakage of a specific element (the light-emitting element  20 , for example) as a result of an excessive current flowing through the element. A typical example of the protective element  60 A is a voltage regulator diode such as a Zener diode. As the Zener diode, an Si diode can be employed. 
     Temperature Measuring Element  60 B 
     The temperature measuring element  60 B is an element used as a temperature sensor for measuring an ambient temperature. For example, a thermistor can be used as the temperature measuring element  60 B. 
     Wiring Line  70   
     The wiring line  70  is formed of a conductor having a linear shape with bonding portions at both ends. In other words, the wiring line  70  includes the bonding portions bonded to other components, at both ends of the linear portion. The wiring line  70  is, for example, a metal wire. Examples of the metal include gold, aluminum, silver, copper, or the like. 
     Lens Member  80   
     The lens member  80  includes one or a plurality of lens surfaces  82 . A surface  81  opposite to the lens surface  82  can be a flat plane. Note that the surface  81  may not be the flat plane. The lens member  80  collimates incident light. In the example illustrated in  FIGS.  4  and  5   , the lens member  80  includes one lens surface  82 . The lens member  80  can be formed of a material having light transmissivity, for example, glass, plastic, or a resin. 
     Beam Combiner  90   
     The beam combiner  90  emits light multiplexed by combining a plurality of incident lights into the same axis. The beam combiner  90  can have a structure to which a plurality of optical elements  91  are bonded. The optical element  91  can be formed of a transparent material such as glass or plastic that transmits visible light. The optical element  91  is achieved by, for example, a dichroic mirror. The dichroic mirror can be formed of a dielectric multilayer film having predetermined wavelength selectivity. The dielectric multilayer film can be formed of Ta 2 O 5 /SiO 2 , TiO 2 /SiO 2 , Nb 2 O 5 /SiO 2 , and the like. 
     Next, the light-emitting device  200  will be described. 
     Light-Emitting Device  200   
     In an example of the light-emitting device  200  to be described below, each of the plurality of light-emitting elements  20  is an edge-emitting semiconductor laser element. The light-emitting device  200  includes the three light-emitting elements  20 . However, the number of the light-emitting elements  20  included in the light-emitting device  200  is not limited to three. 
     In the example of the light-emitting device  200  illustrated by the drawings, the plurality of light-emitting elements  20 , the submount  30 , the optical member  40 A, the photodetector  50 , the plurality of protective elements  60 A, and the temperature measuring element  60 B are disposed in the first mounting region  18   a  included in the mounting surface  11 M of the substrate  11 . The first cap  16  surrounds the components disposed in the first mounting region  18   a . The plurality of lens members  80  and the beam combiner  90  are disposed in the second mounting region  18   b . The second cap  120  surrounds these components disposed in the first mounting region  18   a  and the second mounting region  18   b.    
     The plurality of light-emitting elements  20  include the first light-emitting element  20   a  that emits first light  22   a , and the second light-emitting element  20   b  that emits second light  22   b . Furthermore, the plurality of light-emitting elements  20  may further include the third light-emitting element  20   c  that emits third light  22   c . The plurality of light-emitting elements  20  include two or more light-emitting elements  20  that emit lights of different colors. 
     The plurality of light-emitting elements  20  include the first light-emitting element  20   a , the second light-emitting element  20   b , and the third light-emitting element  20   c  that emit lights of colors different from each other. The first light-emitting element  20   a , the second light-emitting element  20   b , and the third light-emitting element  20   c  emit the lights of colors different from each other that are selected from red, green, or blue. The first light-emitting element  20   a  emits red light, the second light-emitting element  20   b  emits green light, and the third light-emitting element  20   c  emits blue light. 
     The emission end surfaces of the plurality of corresponding light-emitting elements  20  are spaced apart from each other in the X direction. In the top view, the second light-emitting element  20   b  is located between the first light-emitting element  20   a  and the third light-emitting element  20   c . The second light-emitting element  20   b  and the third light-emitting element  20   c  are disposed at positions spaced apart from the first light-emitting element  20   a  in an order of the second light-emitting element  20   b  and the third light-emitting element  20   c . Note that the top view is the plan view as seen along the Y-axis direction. 
     In the top view, the plurality of light-emitting elements  20  include two light-emitting elements  20  in an arrangement relationship in which one light-emitting element  20  is inclined to the other light-emitting element  20 . In the example illustrated in  FIG.  5   , the first light-emitting element  20   a  and the second light-emitting element  20   b  have the arrangement relationship. Further, the second light-emitting element  20   b  and the third light-emitting element  20   c  have the arrangement relationship. Further, the first light-emitting element  20   a  and the third light-emitting element  20   c  have the arrangement relationship. Note that the plurality of light-emitting elements  20  may not have such an arrangement relationship, and, for example, the plurality of light-emitting elements  20  may be disposed in parallel with each other. 
     In the top view, the optical axes of the lights emitted from the plurality of corresponding light-emitting elements  20  are not parallel to each other. Note that these optical axes may be parallel to each other. The two light-emitting elements  20  having the inclined arrangement relationship are inclined in an orientation in which a distance between the two light-emitting elements  20  at a spaced position away from the emission end surface toward an opposite side surface is shorter than a distance between the two light-emitting elements  20  at a position of the emission end surface. Note that the “spaced position” here refers to a position farther at a distance shorter than a length from the emission end surface to the opposite surface of one light-emitting element  20  among the two light-emitting elements  20  having a shorter length from the emission end surface to the opposite surface. 
     In the two light-emitting elements  20  having the inclined arrangement relationship, light traveling on the optical axis of one light-emitting element  20  travels in a direction away from the optical axis in the other light-emitting element  20 . 
     The second light-emitting element  20   b  is disposed such that the optical axis (hereinafter referred to as a second optical axis) is parallel to the Z direction. The term “parallel” used here allows an error within ±2 degrees. The first light-emitting element  20   a  is disposed such that the optical axis (hereinafter referred to as a first optical axis) is inclined relative to the second optical axis. The third light-emitting element  20   c  is disposed such that the optical axis (hereinafter referred to as a third optical axis) is inclined relative to the second optical axis. 
     The plurality of light-emitting elements  20  are disposed on the first mounting region  18   a  via the submount  30 . The lower surface of the submount  30  is bonded to the mounting surface  11 M. The plurality of light-emitting elements  20  are each bonded to the upper surface  30 M of the submount  30  via a metal adhesive such as AuSn, for example. The lower surface of the submount  30  is bonded to the mounting surface  11 M via a metal adhesive such as AuSn and Au particles, for example. 
     In the top view, the light-emitting point of each of the plurality of light-emitting elements  20  is disposed near a side surface of the submount  30  extending in parallel with the X direction. In the light-emitting element  20 , heat concentrates more near the light-emitting point than another place, and thus the emission end surface may not excessively protrude from the submount  30  in terms of heat dissipation. 
     The photodetector  50  is disposed in the first mounting region  18   a . The lower surface of the photodetector  50  is bonded to the mounting surface  11 M. Further, the optical member  40 A is disposed on the light receiving surface  52  of the photodetector  50 . A bonding portion  45  acquired by curing an adhesive for bonding the photodetector  50  and the optical member  40 A is formed between the photodetector  50  and the optical member  40 A. 
     It can be said that the light receiving surface  52  of the photodetector  50  is a bonding surface to which the optical member  40 A is bonded, and the lower surface  44  of the optical member  40 A is the bonding surface  42  to which the photodetector  50  is bonded. Hereinafter, description will be given with the former bonding surface as a first bonding surface and the latter bonding surface as a second bonding surface for a distinction. 
     The first bonding surface  52  and the second bonding surface  42  are bonded via the bonding portion  45 . The bonding portion  45  is in contact with the first bonding surface  52 , the second bonding surface  42 , and the inner side surface  111 . “The bonding portion  45  is in contact with the inner side surface  111 ” means that the adhesive enters the space demarcated by the recessed portion  110 . This makes it possible to suppress the amount of adhesive sticking out from the outer side surface of the optical member  40 A, which leads to providing a light-emitting device having stable quality. When the amount of adhesive sticking out increases, a situation where the adhesive unexpectedly adheres to another component and the bonding portion  45  interferes with the light emitted from the light-emitting element  20  can occur. Furthermore, a contact area of the optical member  40 A with the adhesive increases, and thus occurrence of poor bonding can be suppressed. It can be said that the recessed portion  110  serves as an escape portion of the adhesive. 
     The bonding portion  45  is in contact with the first inner side surface  111   a  and the first inner side surface  111   b  of the first recessed portion  110   a . The bonding portion  45  is in contact with the second inner side surface  111   c  and the second inner side surface  111   d  of the second recessed portion  110   b.    
     The bonding portion  45  is in contact with at least a part of the inner side surface  111 . The bonding portion  45  is not necessarily in contact with the entire inner side surface  111 . The bonding portion  45  can be in contact with the entire inner side surface  111  due to a relationship with the amount of the adhesive and an applied position of the adhesive. 
     It is desirable that the bonding portion  45  is not in contact with the lower surface  113  of the optical member  40 A and is not in contact with at least the highest point of the lower surface  113 . When the bonding portion  45  is in contact with the highest point of the lower surface  113 , the recessed portion  110  is filled with the adhesive, and thus an excessive adhesive may have been used. In this case, the amount of adhesive sticking out may not be sufficiently suppressed. Note that the bonding portion  45  may be in contact with the lower surface  113 . 
     As an exemplary guide for suppressing excessive adhesive sticking out, it is conceivable to set the height h2 of the optical member  40 A to be equal to or more than 20% of the height h1. Furthermore, when the height h2 increases, a thickness between the upper surface  43  and the lower surface  113  is accordingly thinner, and thus the height h2 does not need to be excessively increased. As an exemplary guide, it is conceivable to set the height h2 to be equal to or less than 70% of the height h1. 
     The bonding portion  45  is present between an imaginary flat plane (for example, the imaginary flat plane PL in  FIG.  7 B ) and the bonding surface  42  and is not arranged above the imaginary flat plane. The imaginary flat plane is parallel to the bonding surface  42  and passes through a middle point (for example, the middle point M in  FIG.  7 B ) of the height (the height h1) of the optical member  40 A in the direction perpendicular to the second bonding surface  42 . Note that the direction perpendicular to the second bonding surface  42  is the same direction as the Y direction. 
     In the light-emitting device  200 , the amount of usage of the adhesive forming the bonding portion  45  with the shape of the recessed portion  110  is preferably set such that a height h3 of the bonding portion  45  is in a range from 20% to 80% of the height h2. A light-emitting device having stable quality can be manufactured by increasing an adhesion area and suppressing adhesive sticking out. 
     In the top view, a length of the optical member  40 A in the Z direction can be set in a range from 80% to 120% of a length of the photodetector  50  in the Z direction. It is desirable that the length of the optical member  40 A in the Z direction and the length of the photodetector  50  in the Z direction are the same. In consideration of member tolerance, it can be said that the “same” used here is in a range from 90% to 110%. By making the length of the optical member  40 A and the photodetector  50  in the Z direction the same, a length of the light-emitting device  200  in the Z direction can be suppressed, and a reduction in size of the device can be achieved. 
     In the top view, a length of the optical member  40 A in the X direction is less than a length of the photodetector  50  in the X direction. The photodetector  50  includes an extension region  56  extending in a second direction from a region to which the optical member  40 A is bonded. The second direction is the same direction as the X direction. In the top view, the extension region  56  extends from each of the two outer side surfaces of the optical member  40 A. For a distinction, the extension region  56  extending in the X direction (−X direction) from one outer side surface of the two outer side surfaces is referred to as a first extension region  56   a , and the extension region  56  extending in the X direction (+X direction) from the other outer side surface of the two outer side surfaces is referred to as a second extension region  56   b . Note that, here, indicating the “+X direction” and the “−X direction” intends that both of the directions are parallel to the X-axis but traveling directions thereof are opposite to each other. For example, the +X direction and the −X direction can be distinguished from each other by setting one of the +X direction and −X direction as the second direction and setting the other of the +X direction and −X direction as a third direction (direction opposite to the second direction). 
     The plurality of wiring patterns  54  of the photodetector  50  are arranged in the extension region  56 . The plurality of wiring patterns  54  include one or more wiring patterns  54  arranged in the first extension region  56   a , and one or more wiring patterns  54  arranged in the second extension region  56   b.    
     In the top view, the wiring pattern  54  is arranged at a position spaced apart from the optical member  40 A by a predetermined distance. In the top view, the wiring pattern  54  is not provided in a region of the extension region  56  within the predetermined distance from the optical member  40 A. The predetermined distance is less than a length of the region  41  in the X direction. 
     In the top view, the wiring pattern  54  provided in the first extension region  56   a  is provided in a position spaced apart from one of the two outer side surfaces of the optical member  40 A by the predetermined distance in the −X direction. In the top view, the wiring pattern  54  provided in the second extension region  56   b  is provided in a position spaced apart from the other of the two outer side surfaces of the optical member  40 A by the predetermined distance in the +X direction. 
     A resin adhesive having light transmissivity can be used as the adhesive forming the bonding portion  45 . Note that the adhesive is not limited to the resin adhesive, and another adhesive having light transmissivity in a cured state can also be used. 
     In the top view, the bonding portion  45  can include a portion sticking out from the lower surface  44  of the optical member  40 A. The bonding portion  45  is preferably formed so as to cover at least the plurality of light receiving regions  53  of the photodetector  50 . The reason is that, when a region that is not partially in contact with the bonding portion  45  in the light receiving region  53  is generated, light traveling in a direction from the optical member  40 A toward the light receiving region  53  can be unexpectedly reflected or refracted and cannot reach the light receiving region  53 . 
     By providing the wiring pattern  54  in the position spaced apart from the optical member  40 A by the predetermined distance, the light-emitting device  200  can be manufactured such that the adhesive sticking out from the lower surface  44  of the optical member  40 A does not reach the wiring pattern  54 . In a case in which the bonding portion  45  is formed on the wiring pattern  54 , trouble may unexpectedly occur when the wiring line  70  is bonded to the wiring pattern  54 . 
     The bonding portion  45  is provided on the first bonding surface  52  of the photodetector  50  from the region to which the optical member  40 A is bonded to the extension region  56  and is not provided in the extension region  56  in a position spaced apart from the optical member  40 A by the predetermined distance or longer in the plan view as seen along a direction perpendicular to the first bonding surface  52 . Note that the direction perpendicular to the first bonding surface  52  is the same direction as the Y direction. 
     Each of the plurality of light-emitting elements  20  emits light traveling from the emission end surface to the optical member  40 A. The light emitted from each of the plurality of light-emitting elements  20  passes through the optical member  40 A. The light is incident on the light incident surface of the optical member  40 A. The light incident to the light incident surface is emitted from the light emission surface of the optical member  40 A. 
     Divergent light can be emitted from the light emission surface of the optical member  40 A. An irradiation range in the light emission surface is greater than an irradiation range in the light incident surface of the light emitted from the light-emitting element  20 . The adhesive enters the recessed portion  110 , and thus the adhesive sticking out from the light emission surface can be suppressed. When the amount of adhesive sticking out increases, the bonding portion  45  may partially overlap the irradiation range of the light in the light emission surface, and the bonding portion  45  may unexpectedly refract or reflect the light. The optical member  40 A including the recessed portion  110  can be expected to have an effect of suppressing occurrence of such trouble. Note that such an effect is not limited to a case in which the light emitted from the light emission surface is the divergent light. 
     The partial reflective surface of the optical member  40 A reflects a part of light emitted from each of the plurality of light-emitting elements  20  and incident to the light incident surface and transmits the remaining light. The light transmitted through the partial reflective surface of the optical member  40 A is emitted from the light emission surface, and the light reflected by the partial reflective surface is emitted from the second bonding surface  42 . 
     A part of the first light  22   a  emitted from the first light-emitting element  20   a  passes through the first region  41   a . A part of the second light  22   b  emitted from the second light-emitting element  20   b  passes through the second region  41   b . A part of the third light  22   c  emitted from the third light-emitting element  20   c  passes through the third region  41   c.    
     The photodetector  50  receives a part of the light emitted from each of the plurality of light-emitting elements  20 . In the light receiving region  53  provided in the light receiving surface  52 , the photodetector  50  receives a part of the light emitted from the light-emitting element  20 . 
     A part of the first light  22   a  emitted from the first light-emitting element  20   a  is received in the first light receiving region  53   a . A part of the second light  22   b  emitted from the second light-emitting element  20   b  is received in the second light receiving region  53   b . A part of the third light  22   c  emitted from the third light-emitting element  20   c  is received in the third light receiving region  53   c.    
     In the top view, the light receiving region  53  is disposed in a position through which the optical axis of the light-emitting element  20  passes. In the top view, the first light receiving region  53   a  is disposed in a position through which the optical axis of the first light-emitting element  20   a  passes, the second light receiving region  53   b  is disposed in a position through which the optical axis of the second light-emitting element  20   b  passes, and the third light receiving region  53   c  is disposed in a position through which the optical axis of the third light-emitting element  20   c  passes. 
     In the top view, the optical member  40 A is bonded to the photodetector  50  such that the first region  41   a  overlaps the first light receiving region  53   a  and does not overlap the second light receiving region  53   b . Furthermore, the optical member  40 A is bonded to the photodetector  50  such that the first region  41   a  does not overlap the third light receiving region  53   c.    
     In the top view, the optical member  40 A is bonded to the photodetector  50  such that the second region  41   b  overlaps the second light receiving region  53   b  and does not overlap the first light receiving region  53   a . Furthermore, the optical member  40 A is bonded to the photodetector  50  such that the second region  41   b  does not overlap the third light receiving region  53   c.    
     In the top view, the optical member  40 A is bonded to the photodetector  50  such that the third region  41   c  overlaps the third light receiving region  53   c  and does not overlap the second light receiving region  53   b . Furthermore, the optical member  40 A is bonded to the photodetector  50  such that the third region  41   c  does not overlap the first light receiving region  53   a.    
     A distance between the optical axes of the first light-emitting element  20   a  and the second light-emitting element  20   b  at a position of the light incident surface of the optical member  40 A is greater than a distance between the optical axes of the first light-emitting element  20   a  and the second light-emitting element  20   b  at a position of the emission end surface. The two light-emitting elements  20  are inclined to each other, and thus a distance between two light receiving regions in the photodetector  50  can be increased. In this way, a region in which the recessed portion  110  is to be provided in the optical member  40 A can be easily ensured. A greater width w2 of the recessed portion in the X direction can cause the adhesive to easily enter the recessed portion  110  and can contribute to stabilization of quality of a light-emitting device. 
     In the top view, an inclination angle of the first light-emitting element  20   a  relative to the second light-emitting element  20   b  can be in a range from 50% to 500% of the spread angle in a direction parallel to the emission end surface of the light emitted from the first light-emitting element  20   a . In the top view, an inclination angle of the third light-emitting element  20   c  relative to the second light-emitting element  20   b  can be in a range from 50% to 500% of the spread angle in a direction parallel to the emission end surface of the light emitted from the third light-emitting element  20   c . In the illustrated light-emitting device  200 , the spread angle in the direction parallel to the emission end surface is the slow-axis spread angle. Note that a value of the spread angle here is a value of a half angle for comparison with the inclination angle. By setting the inclination angle to be equal to or more than 50% with respect to the spread angle of light, the width w2 of the recessed portion  110  can be easily ensured while disposing the plurality of light-emitting elements  20  in close proximity. By setting the inclination angle to be equal to or less than 500% with respect to the spread angle of light, a size of the light-emitting device  200  in the X direction can be suppressed while ensuring the width w2 of the recessed portion  110 . 
     In the light-emitting device  200 , the length of the optical member  40 A in the X direction can be greater than a length of the submount  30  in the X direction, and the length of the photodetector  50  in the X direction can be greater than the length of the optical member  40 A in the X direction. In this way, a reduction in size of the light-emitting device  200  can be achieved by a relationship with the wiring region  14  to be described below. 
     The first inner side surface  111   a  is arranged in a position through which a first imaginary line does not pass. The first imaginary line is an imaginary straight line that coincides with an optical path at an outer edge of the main portion of the first light  22   a  closest to the first inner side surface  111   a  and incident to the light incident surface of the optical member  40 A and reaching the partial reflective surface. 
     The first inner side surface  111   a  is arranged in a position through which a second imaginary line does not pass. The second imaginary line is an imaginary straight line that coincides with an optical path at an outer edge of the main portion of the second light  22   b  closest to the first inner side surface  111   a  and incident to the light incident surface of the optical member  40 A and reaching the partial reflective surface. Furthermore, the first inner side surface  111   b  is provided in a position through which the first imaginary line and the second imaginary line do not pass. 
     The second inner side surface  111   c  is arranged in a position through which a third imaginary line does not pass. The third imaginary line is an imaginary straight line that coincides with an optical path at the outer edge of the main portion of the second light  22   b  closest to the second inner side surface  111   c  and incident to the light incident surface of the optical member  40 A and reaching the partial reflective surface. 
     The second inner side surface  111   c  is arranged in a position through which a fourth imaginary line does not pass. The fourth imaginary line is an imaginary straight line that coincides with an optical path at an outer edge of the main portion of the third light  22   c  closest to the second inner side surface  111   c  and incident to the light incident surface of the optical member  40 A and reaching the partial reflective surface. Furthermore, the second inner side surface  111   d  is arranged in a position through which the third imaginary line and the fourth imaginary line do not pass. 
     The plurality of wiring regions  14  can be provided in a region on the mounting surface  11 M located laterally in the X direction relative to the submount  30 . The plurality of wiring regions  14  include the wiring region  14  electrically connected to at least one of the plurality of light-emitting elements  20 . The plurality of wiring regions  14  include the wiring region  14  in which the protective element  60 A is disposed. The plurality of wiring regions  14  include the wiring region  14  in which the temperature measuring element  60 B is disposed. 
     The light-emitting element  20  is electrically connected to two wiring regions  14  via the corresponding wiring lines  70 . The temperature measuring element  60 B is disposed on one wiring region  14  of the two wiring regions  14  and is electrically connected to the other wiring region  14  of the two wiring regions  14  via the wiring line  70 . 
     The first cap  16  is mounted on the mounting surface  11 M. The first cap  16  is bonded to the peripheral region  11 P surrounding the first mounting region  18   a . The plurality of light-emitting elements  20  are hermetically sealed by the substrate  11  and the first cap  16 . By hermetically sealing the space in which the light-emitting element  20  is disposed, a deterioration in quality due to dust gathering can be suppressed. 
     The light emitted from each of the plurality of light-emitting elements  20  is incident on the optical member  40 A, and a part of the light is reflected by the partial reflective surface, is incident on the light receiving region  53 , and is received in the photodetector  50 . The light incident on the light receiving region  53  is used as the monitor light. Another part of the light incident on the optical member  40 A is transmitted through the partial reflective surface and is emitted from the light emission surface toward the side wall portion  12  of the package  10 . The light emitted from the light emission surface of the optical member  40 A is incident on the light incident surface  10 A of the side wall portion  12 , is transmitted through the light-transmissive region, and is emitted from the light extraction surface  10 B. 
     In the light-emitting device  200 , the lens member  80  is disposed in the second mounting region  18   b  of the substrate  11 . The beam combiner  90  is disposed in the second mounting region  18   b  of the substrate  11 . Here, in the Z direction, relative to the plurality of light-emitting elements  20 , a direction facing the side wall portion  12  on which light emitted from each of the plurality of light-emitting elements  20  is incident is referred to as front of a member, and a direction facing the side wall portion  12  located opposite to the side wall portion  12  on which the light is incident is referred to as rear of the member. The light-emitting element  20 , the lens member  80 , and the beam combiner  90  are disposed in this order from the rear to the front in the Z direction. The lens member  80  is disposed in front of the light-emitting element  20 , and receives the light emitted from the light-emitting element  20 . The beam combiner  90  is disposed in front of the lens member  80 , and receives the light emitted from the lens member  80 . 
     The plurality of lights incident on the beam combiner  90  are combined onto the same axis, and the multiplexed light is emitted from the beam combiner  90 . The multiplexed light emitted from the beam combiner  90  is transmitted through an incident surface of the lid member  130  and is emitted from an emission surface of the lid member  130  to the outside of the light-emitting device  200 . 
     Second Embodiment 
     A light-emitting device  300  according to a second embodiment will be described. A schematic structure of a main portion according to the second embodiment will be described with reference to  FIGS.  8 A and  8 B .  FIG.  8 A  is a top view of an optical member and a photodetector according to the second embodiment.  FIG.  8 B  is a cross-sectional view of the optical member and the photodetector taken along a section line VIIIB-VIIIB in  FIG.  8 A . Note that, in the second embodiment, an optical member  40 B being a modification example of the optical member  40 A according to the first embodiment will be described. Thus, because a configuration other than the optical member  40 B is the same as the configuration described in the light-emitting device  200  according to the first embodiment, description thereof will be omitted. 
     In the first embodiment, the recessed portion  110  having the slit shape is formed in the optical member  40 A, but, in the second embodiment, a plurality of through holes  121   a  and  121   b  each having a cylindrical shape are deined as the recessed portion  110  in the optical member  40 B. Furthermore, a plurality of through holes  122   a  and  122   b  each having a cylindrical shape are defined as the recessed portion  110  in the optical member  40 B. In other words, in the present description, a word of the recessed portion  110  is used as a word widely including a shape that demarcates a space recessed upward from the lower surface  44  and is also used as a word including a shape penetrating from the lower surface  44  of the optical member  40 A to the upper surface  43  of the optical member  40 A such as the through hole  121   a.    
     In a plan view as seen along a direction (Y-axis direction) perpendicular to the bonding surface  42 , the through holes  121   a  and  121   b  are arranged between a first region  41   a  and a second region  41   b . In the plan view as seen along the direction (Y-axis direction) perpendicular to the bonding surface  42 , the through holes  122   a  and  122   b  are arranged between the second region  41   b  and a third region  41   c.    
     For example, a diameter w3 of a circular cross-section of each of the through holes  121   a  and  121   b  having the cylindrical shape is 0.15 mm. The diameter w3 of the circular cross-section of each of the through holes  122   a  and  122   b  is 0.15 mm. Note that, in  FIGS.  8 A and  8 B , the two through holes  121   a  and  121   b  are formed between the first region  41   a  and the second region  41   b , and the two through holes  122   a  and  122   b  are formed between the second region  41   b  and the third region  41   c , but one through hole may be formed, or three or more through holes may be formed. 
     Third Embodiment 
     A light-emitting device  400  according to a third embodiment will be described. A schematic structure of a main portion according to the third embodiment will be described with reference to  FIGS.  9 A and  9 B .  FIG.  9 A  is a top view of an optical member and a photodetector according to the third embodiment.  FIG.  9 B  is a cross-sectional view of the optical member and the photodetector taken along a section line IXB-IXB in  FIG.  9 A . Note that, in the third embodiment, a bonding portion  45 B formed of an adhesive between an optical member  40 A and a photodetector  50  is different from the bonding portion  45  according to the first embodiment. Because a configuration other than the bonding portion  45 B is the same as the configuration described in the light-emitting device  200  according to the first embodiment, description thereof will be omitted. 
     In the light-emitting device  200  according to the first embodiment, the adhesive reaches a surface of the light receiving region  53  of the photodetector  50 , and the bonding portion  45  covers the light receiving region  53 , but, in the light-emitting device  400  according to the third embodiment, the bonding portion  45 B is not formed directly above a light receiving region  53 . In the top view, the bonding portion  45 B is formed so as not to overlap any of a plurality of the light receiving regions  53 . In this way, the amount of usage of the adhesive can be further reduced than when the bonding portion  45  is formed so as to cover the light receiving region  53 . Furthermore, by reducing the amount of usage of the adhesive, the amount of adhesive sticking out can also be suppressed. 
     For example, the bonding portion  45 B can be formed by applying the adhesive to a position in which the recessed portion  110  of the optical member  40 A is disposed on a first bonding surface  52  of the photodetector  50 , and then bonding the first bonding surface  52  and a second bonding surface  42 . 
     Fourth Embodiment 
     A light-emitting device  500  according to a fourth embodiment will be described. A schematic structure of a main portion according to the fourth embodiment will be described with reference to  FIGS.  10 A and  10 B .  FIG.  10 A  is a top view of an optical member and a photodetector according to the fourth embodiment.  FIG.  10 B  is a cross-sectional view of the optical member and the photodetector taken along a section line XB-XB in  FIG.  10 A . Note that, in the fourth embodiment, an optical member  40 C being a modification example of the optical member  40 A according to the first embodiment will be described. Furthermore, a bonding portion  45 C formed of an adhesive between the optical member  40 C and a photodetector  50  will be described. Because a configuration other than the optical member  40 C and the bonding portion  45 C is the same as the configuration described in the light-emitting device  200  according to the first embodiment, description thereof will be omitted. Note that a maximum width w4 of a recessed portion  110  according to the fourth embodiment in the X direction can be in a range from 0.05 mm to 0.5 mm. 
     In the first embodiment, one recessed portion  110  having the slit shape is formed between adjacent light receiving regions  53  in the top view, but, in the fourth embodiment, two recessed portions  110  each having the slit shape are formed between adjacent light receiving regions  53  in the top view. Furthermore, the two recessed portions  110  are provided side by side in the same direction as a direction in which the light receiving regions  53  are disposed side by side. 
     The optical member  40 C and the photodetector  50  are bonded such that two first recessed portions  110   a  are disposed between the first light receiving region  53   a  and the second light receiving region  53   b , and two second recessed portions  110   b  are disposed between the second light receiving region  53   b  and the third light receiving region  53   c . An interval between the two first recessed portions  110   a  in the X direction is less than a width of the first light receiving region  53   a  in the X direction. An interval between the two second recessed portions  110   b  in the X direction is less than a width of the third light receiving region  53   c  in the X direction. 
     A first recessed portion  110   a  closer to the first light receiving region  53   a  among the two first recessed portions  110   a  includes a first inner side surface  111   a  and a first inner side surface  111   b , and the first inner side surface  111   a  is closer to the first light receiving region  53   a  than the first inner side surface  111   b . Furthermore, a first recessed portion  110   a  farther from the first light receiving region  53   a  among the two first recessed portions  110   a  includes the first inner side surface  111   a  and the first inner side surface  111   b , and the first inner side surface  111   a  is closer to the first light receiving region  53   a  than the first inner side surface  111   b.    
     A second recessed portion  110   b  closer to the second light receiving region  53   b  among the two second recessed portions  110   b  includes a second inner side surface  111   c  and a second inner side surface  111   d , and the second inner side surface  111   c  is closer to the second light receiving region  53   b  than the second inner side surface  111   d . Furthermore, a second recessed portion  110   b  farther from the second light receiving region  53   b  among the two second recessed portions  110   b  includes the second inner side surface  111   c  and a second inner side surface  111   d , and the second inner side surface  111   c  is closer to the second light receiving region  53   b  than the second inner side surface  111   d.    
     Similar to the bonding portion  45 B according to the third embodiment, the bonding portion  45 C is not formed directly above the light receiving region  53 . Furthermore, the bonding portion  45 C is in contact with the first inner side surface  111   b  of the first recessed portion  110   a  closer to the first light receiving region  53   a , and the first inner side surface  111   a  of the first recessed portion  110   a  farther from the first light receiving region  53   a , among the two first recessed portions  110   a . The bonding portion  45 C is in contact with a lower surface  44  sandwiched between the two first recessed portions  110   a . The bonding portion  45 C is continuously in contact with the first inner side surface  111   b , the first inner side surface  111   a , and the lower surface  44 . In this way, the optical member  40 C can be stably bonded to the photodetector  50 . 
     The bonding portion  45 C is not in contact with the first inner side surface  111   a  of the first recessed portion  110   a  closer to the first light receiving region  53   a , and the first inner side surface  111   b  of the first recessed portion  110   a  farther from the first light receiving region  53   a , among the two first recessed portions  110   a . By providing the adhesive so as to form such a bonding portion  45 C, the optical member  40 C can be bonded to the photodetector  50  such that the adhesive does not extend to the light receiving region  53 . Note that the bonding portion  45 C may be in contact with the first inner side surface  111   a  of the first recessed portion  110   a  closer to the first light receiving region  53   a  and the first inner side surface  111   b  of the first recessed portion  110   a  farther from the first light receiving region  53   a.    
     When the bonding portion  45 C is in contact with both of two first inner side surfaces  111  of the first recessed portion  110   a , an area in which the bonding portion  45 C is in contact with the first inner side surface  111   a  of the first recessed portion  110   a  closer to the first light receiving region  53   a  among the two first recessed portions  110   a  is preferably less than an area in which the bonding portion  45 C is in contact with the first inner side surface  111   b  of this first recessed portion  110   a . Furthermore, an area in which the bonding portion  45 C is in contact with the first inner side surface  111   a  of the first recessed portion  110   a  farther from the first light receiving region  53   a  among the two first recessed portions  110   a  is preferably greater than an area in which the bonding portion  45 C is in contact with the first inner side surface  111   b  of this first recessed portion  110   a . By forming the bonding portion  45 C in such a manner, the bonding portion  45 C partially covering the light receiving region  53  can be easily avoided. 
     The bonding portion  45 C is in contact with the second inner side surface  111   d  of the second recessed portion  110   b  closer to the second light receiving region  53   b , and the second inner side surface  111   c  of the second recessed portion  110   b  farther from the second light receiving region  53   b , among the two second recessed portions  110   b . The bonding portion  45 C is in contact with the lower surface  44  sandwiched between the two second recessed portions  110   b . The bonding portion  45 C is continuously in contact with the second inner side surface  111   d , the second inner side surface  111   c , and the lower surface  44 . In this way, the optical member  40 C can be stably bonded to the photodetector  50 . 
     The bonding portion  45 C is not in contact with the second inner side surface  111   c  of the second recessed portion  110   b  closer to the second light receiving region  53   b , and the second inner side surface  111   d  of the second recessed portion  110   b  farther from the second light receiving region  53   b , among the two second recessed portions  110   b . By providing the adhesive so as to form such a bonding portion  45 C, the optical member  40 C can be bonded to the photodetector  50  such that the adhesive does not extend to the light receiving region  53 . Note that the bonding portion  45 C may be in contact with the second inner side surface  111   c  of the second recessed portion  110   b  closer to the second light receiving region  53   b  and the second inner side surface  111   d  of the second recessed portion  110   b  farther from the second light receiving region  53   b.    
     When the bonding portion  45 C is in contact with both of two second inner side surfaces  111  of the second recessed portion  110   b , an area in which the bonding portion  45 C is in contact with the second inner side surface  111   c  of the second recessed portion  110   b  closer to the second light receiving region  53   b  among the two second recessed portions  110   b  is preferably less than an area in which the bonding portion  45 C is in contact with the second inner side surface  111   d  of this second recessed portion  110   b . Furthermore, an area in which the bonding portion  45 C is in contact with the second inner side surface  111   c  of the second recessed portion  110   b  farther from the second light receiving region  53   b  among the two second recessed portions  110   b  is preferably greater than an area in which the bonding portion  45 C is in contact with the second inner side surface  111   d  of this second recessed portion  110   b . By forming the bonding portion  45 C in such a manner, the bonding portion  45 C partially covering the light receiving region  53  can be easily avoided. 
     For example, the bonding portion  45 C can be formed by applying the adhesive to a position in which the lower surface  44  sandwiched between the two first recessed portions  110   a  of the optical member  40 C is disposed on a first bonding surface  52  of the photodetector  50 , and then bonding the first bonding surface  52  and a second bonding surface  42 . 
     Head-Mounted Display 
       FIG.  11    is a side view schematically illustrating a configuration example of a head-mounted display  600  including the light-emitting device  200  ( 300 ,  400 , or  500 ) according to the embodiments of the present disclosure. Hereinafter, the light-emitting device  200  will be described as an example, but the head-mounted display  600  may include the light-emitting devices  300 ,  400 , or  500  instead of the light-emitting device  200 . The head-mounted display  600  includes a temple  650  and a waveguide  660  connected to the temple  650 . The waveguide  660  includes a light emission region such as a diffraction grating, for example. Laser light incident on the waveguide  660  can be emitted from the light emission region of the waveguide  660  toward a retina of an eye of a user. 
     One end of the temple  650  is located proximate to the waveguide  660 , in other words, proximate to a nose of the user, and the other end of the temple  650  is located opposite to the waveguide  660 , in other words, proximate to an ear of the user. In  FIG.  11   , directions toward both ends of the temple  650  are parallel to a direction of the optical axis of the light emitted from the light-emitting device  200 . In the illustrated by the drawings, the X, Y, and Z directions of the light-emitting device  200  in  FIG.  1    match the X, Y, and Z directions of the light-emitting device  200  in  FIG.  11   . Based on a user wearing the head-mounted display  600 , the direction of the optical axis is substantially parallel to a direction from an ear toward an eye of the user (or vice versa) in the side view. 
     In the example of the head-mounted display  600  illustrated in  FIG.  11   , the light-emitting device  200  is supported inside the temple  650 . In  FIG.  11   , the light-emitting device  200  is described as being visible on a side surface, but the light-emitting device  200  is actually in a state where an appearance is not visually recognized from the outside. For example, the size, in the X direction, of the light-emitting device  200  illustrated in  FIG.  1    is in a range from 3 mm to 15 mm and is less than the size, in the Z direction (an extending direction of the temple  650  in  FIG.  11   ), of the light-emitting device  200 . 
     The light-emitting device  200  is preferably mounted on the head-mounted display  600  such that the direction of the optical axis of the light emitted from the light-emitting device  200  and the extending direction of the temple of the head-mounted display  600  are parallel to each other. A width of the temple  650  in the X direction can be reduced by the light-emitting device  200  reduced in size in a direction perpendicular to the optical axis. As illustrated, a length of the temple  650  has a length that ensures a distance from an eye to an ear of a user, and thus, as long as the size in the direction of the optical axis of the light emitted from the light-emitting device  200  is small to a certain extent, the size in the direction of the optical axis of the light emitted from the light-emitting device  200  does not contribute to a reduction in size of the head-mounted display  600  even when the size in the direction of the optical axis of the light emitted from the light-emitting device  200  is further reduced. 
     In this embodiment, from the light-emitting device  200 , a collimated beam of each of the first light  22   a , the second light  22   b , and the third light  22   c  can be emitted from a narrow region onto the same axis. The first light  22   a , the second light  22   b , and the third light  22   c  are a laser beam of any color of red, green, and blue. The laser beam of each color is scanned by a MEMS element such as a micromirror, for example, and travels inside the waveguide  660 , and then forms an image on a retina of a user. Display of a color image may be performed by a field sequential method. In that case, the first light  22   a , the second light  22   b , and the third light  22   c  are sequentially emitted. In order to monitor intensity of the first light  22   a , the second light  22   b , and the third light  22   c , the photodetector  50  included in the light-emitting device  200  can be used, for example. Note that the light-emitting device  200  ( 300 ,  400 , or  500 ) may be disposed on the head-mounted display  600  such that the Y direction and the X direction in  FIG.  11    match the X direction and the Y direction in  FIG.  1   , respectively. 
     Although the embodiments according to the present invention have been described above, the light-emitting device according to the present invention is not strictly limited to the light-emitting devices of the embodiments. In other words, the present invention can be achieved without being limited to the external shape or structure of the light-emitting device disclosed by each of the embodiments. For example, a light-emitting device that does not include a protective element may be applicable. Furthermore, it can be applied without requiring all the components being sufficiently provided. For example, in a case in which some of the components of the light-emitting device disclosed by the embodiments are not stated in the scope of the claims, the degree of freedom in design by those skilled in the art such as substitutions, omissions, shape modifications, and material changes for those components is allowed, and then the invention stated in the scope of the claims being applied to those components is specified. 
     The light-emitting device according to each of the embodiments can be used for a head-mounted display, a projector, lighting, a display, and the like.