Light source device

Abstract

To provide a light source device suitable for downsizing.SOLUTION: A light source device 100 comprises: a first substrate 10 including a first mounting surface 10a; a second substrate 11 including a second mounting surface 11a opposed to the first mounting surface; a first laser diode 30 supported on the first mounting surface; a first photodetector 40 supported on the second mounting surface; and a frame body 50 defining a space V in which the first laser diode and the first photodetector are accommodated. The frame body 50 includes a window part 50f, and the window part 50f includes an incidence plane 50c to which laser light 14 emitted from the first laser diode is incident, and an emission plane 50d from which the laser light emitted from the first laser diode is emitted. The laser light emitted from the first laser diode is partially transmitted, and the laser light emitted from the first laser diode is partially reflected. The first photodetector 40 detects light reflected by the window part in the laser light emitted from the first laser diode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a light source device. [Background technology]

[0002] Light source devices equipped with a photodetector for monitoring the intensity of laser light have been developed. Patent Document 1 discloses a light source device equipped with a photosensor that receives a portion of the laser light emitted from a surface-emitting laser array and detects the intensity of the laser light. In this light source device, the surface-emitting laser array and the photosensor are arranged in the same space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-114097 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a light source device suitable for miniaturization. [Means for solving the problem]

[0005] In a non-limiting exemplary embodiment, the light source device of the present disclosure comprises a first substrate having a first mounting surface, a second substrate having a second mounting surface opposite the first mounting surface, a first laser diode supported directly or indirectly on the first mounting surface, a first photodetector supported directly or indirectly on the second mounting surface, and a frame body defining a space to accommodate the first laser diode and the first photodetector, wherein the frame body has a window portion, and the window portion has an incident surface onto which laser light emitted from the first laser diode is incident and an exit surface from which the laser light emitted from the first laser diode exits, and transmits a portion of the laser light emitted from the first laser diode and reflects a portion of the laser light emitted from the first laser diode, and the first photodetector detects the light of the laser light emitted from the first laser diode reflected by the window portion. [Effects of the Invention]

[0006] According to an exemplary embodiment of the present disclosure, a light source device suitable for miniaturization is provided. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view parallel to the XY plane of a light source device according to an exemplary embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view parallel to the YZ plane of the light source device according to the exemplary embodiment of the present disclosure. [Figure 3] FIG. 3 is a perspective view schematically showing a laser diode bonded to a submount fixed to one of a pair of substrates. [Figure 4] FIG. 4 is a perspective view schematically showing a photodetector mounted on the other of the pair of substrates. [Figure 5] FIG. 5 is a cross-sectional view parallel to the YZ plane of another configuration example of a light source device according to an exemplary embodiment of the present disclosure. [Figure 6] FIG. 6 is a cross-sectional view parallel to the YZ plane of yet another configuration example of a light source device according to an exemplary embodiment of the present disclosure. [Figure 7]FIG. 7 is a cross-sectional view parallel to the YZ plane of a modified example of the light source device according to the exemplary embodiment of the present disclosure. [Figure 8] FIG. 8 is a cross-sectional view parallel to the YZ plane of a modified example of the light source device according to the exemplary embodiment of the present disclosure. [Figure 9] FIG. 9 is a cross-sectional view parallel to the YZ plane of a modified example of the light source device according to the exemplary embodiment of the present disclosure. [Figure 10] FIG. 10 is a cross-sectional view parallel to the YZ plane of a modified example of the light source device according to the exemplary embodiment of the present disclosure. [Figure 11] FIG. 11 is a cross-sectional view parallel to the XY plane of a light source device including multiple laser diodes and multiple photodetectors according to an exemplary embodiment of the present disclosure. [Figure 12] FIG. 12 is a perspective view schematically showing a plurality of laser diodes bonded to a submount fixed to one of a pair of substrates. [Figure 13A] FIG. 13A is a perspective view schematically showing a plurality of photodetectors mounted on the other of the pair of substrates. [Figure 13B] FIG. 13B is a perspective view that schematically shows a configuration in which a plurality of photodetectors are integrated and mounted on the other of the pair of substrates. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following embodiments are merely examples, and the light source device according to the present disclosure is not limited to the following embodiments. For example, the numerical values, shapes, materials, steps, and the order of the steps shown in the following embodiments are merely examples, and various modifications are possible as long as no technical contradictions occur. Furthermore, the various aspects described below are merely examples, and various combinations are possible as long as no technical contradictions occur.

[0009] The dimensions, shapes, etc. of components shown in the drawings may be exaggerated for clarity. Therefore, the dimensions, shapes, and size relationships between components of an actual light source device may not be reflected. Also, in order to avoid overly complicated drawings, some elements may be omitted from the illustration.

[0010] In the following description, components having substantially the same functions are denoted by common reference symbols, and their descriptions may be omitted. Terms indicating specific directions or positions (e.g., "upper," "lower," "right," "left," and other terms including these terms) may be used. However, these terms are used merely to facilitate understanding of relative directions or positions in the referenced drawings. As long as the relationship of relative directions or positions indicated by terms such as "upper" and "lower" in the referenced drawings is the same, drawings other than those disclosed in this disclosure, actual products, manufacturing equipment, etc. may not be arranged in the same manner as in the referenced drawings.

[0011] In this specification, terms such as "first," "second," and "third" are used as labels to distinguish the objects to be added, and are not intended to limit the number, order, sequence, etc.

[0012] An example of the configuration of a light source device 100 according to this embodiment will be described with reference to FIGS.

[0013] FIG. 1 is a cross-sectional view parallel to the XY plane of a light source device 100 according to this embodiment. In FIG. 1, an emission end face 30e of a laser diode 30 and a light receiving portion 40r of a photodetector 40 are shown. In the accompanying drawings, mutually orthogonal X-, Y-, and Z-axes are shown for reference. FIG. 2 is a cross-sectional view parallel to the YZ plane of a light source device 100 according to this embodiment. FIG. 3 is a perspective view schematically showing a laser diode 30 bonded to a submount 20 on a substrate 10. In FIG. 3, a frame 50 is shown in a see-through state so that the internal structure of the light source device 100 can be seen, and the central axis of the laser light 14 emitted from the laser diode 30 is indicated by a dashed line. FIG. 4 is a perspective view schematically showing a photodetector 40 mounted on a substrate 11. is.

[0014] The light source device 100 in this embodiment includes a first substrate 10, a second substrate 11, a submount 20, at least one laser diode 30, at least one photodetector 40, and a frame 50. In the example of FIG. 1, the light source device 100 includes one laser diode 30 and one photodetector 40. The light source device 100 may include a protective element 60, which will be described later, but the protective element is not shown in FIG. 1 to avoid complicating the drawing. The light source device 100 may further include a temperature sensor (not shown), such as a thermistor, for measuring the internal temperature.

[0015] An example of the shape of light source device 100 in this embodiment is a substantially rectangular parallelepiped, as shown in Fig. 3. For example, the size of light source device 100 in the X direction may be approximately 1.0 mm to 5.0 mm, the size in the Z direction may be approximately 2.0 mm to 5.0 mm, and the thickness in the Y direction may be approximately 1.0 mm to 3.0 mm. Light source device 100 may be suitably used as a light source for, for example, head-mounted displays, projectors, lighting devices, etc.

[0016] The first substrate 10 and the second substrate 11 form a pair of substrates. The first substrate 10 has a first mounting surface 10a that directly or indirectly supports the laser diode 30. The second substrate 11 has a second mounting surface 11a that directly or indirectly supports the photodetector 40. Hereinafter, each of the first and second substrates will be simply referred to as a "substrate," and each of the first and second mounting surfaces will be simply referred to as a "mounting surface." The substrates are plate-shaped members. The pair of substrates 10 and 11 are arranged so that the mounting surfaces 10a and 11a face each other. The pair of substrates 10 and 11 can be formed primarily from ceramic. However, they are not limited to ceramic and may also be formed from metal. For example, ceramics such as aluminum nitride, silicon nitride, aluminum oxide, and silicon carbide can be used as the primary material for the substrates; metals such as copper, aluminum, and iron can be used; and composites such as copper molybdenum, copper-diamond composites, and copper tungsten can be used as the primary material for the substrates. Other materials that can be used include silicon and resin. However, when metal is used, the mounting surfaces 10a and 11a must be insulated in order to provide a conductive wiring layer on the substrate.

[0017] The substrate 10 has a conductor wiring layer electrically connected to the laser diode 30. As shown in FIG. 3, a pair of electrode pads pd for mounting the protection element 60 is provided on the mounting surface 10a of the substrate 10 as part of the conductor wiring layer. The substrate 11 has a conductor wiring layer electrically connected to the photodetector 40. As shown in FIG. 4, a pair of electrode pads pd for mounting the photodetector 40 is provided on the mounting surface 11a of the substrate 11 as part of the conductor wiring layer. By electrically connecting the laser diode 30 to the conductor wiring layer of one of the pair of substrates 10 and 11 and electrically connecting the photodetector 40 to the conductor wiring layer of the other, wiring of the laser diode 30 and the photodetector 40 becomes easy. Furthermore, since the wiring can be provided separately on each of the substrates 10 and 11, the light source device 100 can be made smaller.

[0018] The conductor wiring layer may be formed from a metal material such as tungsten, molybdenum, nickel, gold, silver, platinum, titanium, copper, aluminum, ruthenium, etc. The conductor wiring layer may have a multi-layer structure in which each layer is electrically connected through vias.

[0019] The submount 20 is a heat dissipation member, and typically has a rectangular parallelepiped shape, but is not limited to this. The submount 20 plays a role in dissipating heat generated by the laser diode 30. From the viewpoint of further improving heat dissipation, the submount 20 is preferably made of a material with a higher thermal conductivity than the laser diode 30. Examples of such materials include ceramic materials such as aluminum nitride, silicon nitride, aluminum oxide, and silicon carbide, as well as copper, aluminum, silver, iron, nickel, molybdenum, tungsten, and copper molybdenum. A metal containing at least one selected from the group consisting of the above is used.

[0020] The submount 20 is bonded to the mounting surface 10a of the substrate 10. Such bonding can be achieved through a layer of inorganic material such as metal, or an organic material. However, when using a laser diode that emits blue or green light, it is preferable to avoid using organic materials, considering the effect of dust collection by the laser light.

[0021] The submount 20 has a mounting surface 20a on which the laser diode 30 is disposed. In the example of FIG. 3, electrode pads pd electrically connecting to the laser diode 30 are formed on the mounting surface 20a of the submount 20. The laser diode 30 is indirectly mounted on the mounting surface 10a of the substrate 10 while being bonded to the submount 20. However, the laser diode 30 can also be bonded directly to the mounting surface 10a of the substrate 10 without the submount 20. Therefore, although the submount 20 is not an essential component in this embodiment, using the submount 20 can improve heat dissipation. Furthermore, it can also facilitate adjustment of the position of the light-emitting point of the laser diode 30 in the height direction.

[0022] The laser diode 30 has a p-side electrode, an n-side electrode, and a semiconductor stack (not shown) including a p-side semiconductor layer, an n-side semiconductor layer, and an active layer located between these layers. By applying a voltage to the p-side electrode and the n-side electrode to pass a current through the inside, laser light 14 is emitted from an emission facet 30e of the laser diode 30. In this embodiment, the laser diode 30 is an edge-emitting type having an end face from which the laser light is emitted, but it may also be a vertical cavity surface-emitting laser (VCSEL).

[0023] For example, a laser diode that emits blue light, a laser diode that emits green light, or a laser diode that emits red light can be used as the laser diode 30. Also, a laser diode that emits other light, such as near-infrared light or ultraviolet light, may be used.

[0024] In this specification, blue light is light having a peak emission wavelength in the range of 420 nm to 494 nm, green light is light having a peak emission wavelength in the range of 495 nm to 570 nm, and red light is light having a peak emission wavelength in the range of 605 nm to 750 nm.

[0025] Examples of laser diodes that emit blue light or green light include laser diodes that include nitride semiconductors. Examples of nitride semiconductors that can be used include GaN, InGaN, and AlGaN. Examples of laser diodes that emit red light include those that include InAlGaP, GaInP, GaAs, and AlGaAs semiconductors.

[0026] The laser beam emitted from a laser diode has a divergence and forms an elliptical far-field pattern (hereinafter referred to as "FFP") on a plane parallel to the output facet of the laser beam. The FFP is determined by the light intensity distribution of the laser beam at a position away from the output facet. In this light intensity distribution, the 1 / e 2 The portion having the above intensity may be called the beam cross section.

[0027] 2, the actual laser light 14 diverges and spreads after being emitted from the emission end face 30e of the laser diode 30. Therefore, the laser light 14 can be collimated or converged by an optical system including a lens (not shown). Such an optical system can be provided inside or outside the light source device 100.

[0028] The photodetector 40 monitors the intensity of the laser beam 14 emitted from the laser diode 30. More specifically, the photodetector 40 has a light receiving unit 40r, and receives at least a portion of the total area of ​​the beam cross section of the laser beam 14 emitted from the laser diode 30 or at least a portion of the total laser output of the laser beam 14 emitted from the laser diode 30 at the light receiving unit 40r to monitor the intensity of the laser beam 14. An example of the light receiving unit 40r is a photoelectric conversion element such as a photodiode, and it is preferably provided at a position facing an incident surface 50c of a window 50f provided in the frame 50, which will be described later. The intensity of the laser beam can also be referred to as optical power.

[0029] The photodetector 40 detects, as monitor light, light reflected by at least one of an entrance surface 50c and an exit surface 50d of a window portion 50f of the frame body 50, which will be described later. The photodetector 40 requires monitor light of, for example, about 5 mW to monitor the intensity of the laser light 14 emitted from the laser diode 30. In this embodiment, for example, about 5% of the laser light 14 emitted from the laser diode 30 is used as monitor light, and the remaining about 95% is extracted to the outside.

[0030] The photodetector 40 is directly or indirectly supported on the mounting surface 11a of the substrate 11. In the example of FIG. 4, the photodetector 40 is electrically connected to a pair of electrode pads pd formed on the mounting surface 11a. Note that, like the laser diode 30, the photodetector 40 may be indirectly supported on the substrate 11 via a submount. In this case, the height of the photodetector 40 in the Y direction can be easily adjusted. In the example of FIG. 1, the thickness of the laser diode 30 in the Y direction may be, for example, about 0.1 mm, and the thickness of the photodetector 40 in the Y direction may be, for example, about 0.4 mm. Furthermore, the laser diode 30 and the photodetector 40 may be disposed closely to each other in the Y direction, with a gap of, for example, about 0.05 mm between them.

[0031] As shown in FIG. 1 or 2, when viewed from a direction perpendicular to the mounting surface 10a (i.e., the Y-axis direction), the photodetector 40 at least partially overlaps the laser diode 30. In the example of FIG. 1, the photodetector 40 is disposed directly above the laser diode 30. This arrangement prevents the laser light 14 emitted from the laser diode 30 from directly entering the light-receiving portion 40r of the photodetector 40, allowing the intensity of the laser light 14 to be monitored accurately. Furthermore, as will be described later, a portion of the laser light 14 reflected by the window portion 50f of the frame 50 is more likely to be received by the light-receiving portion 40r of the photodetector 40. However, the relative positional relationship or size relationship of the photodetector 40 with respect to the laser diode 30 in the example of FIG. 1 is merely exemplary and is not limited thereto. For example, the width of the laser diode 30 may be longer than the width of the photodetector 40 in the X-direction. Alternatively, the first line segment that approximately bisects the light-emitting end face 30e of the laser diode 30 does not have to coincide with the second line segment that approximately bisects the light-receiving portion 40r of the photodetector 40. Furthermore, in the example of FIG. 2, the end face of the light-receiving portion 40r is located at the same position as the light-emitting end face 30e in the Z direction, but this is not limited to this. The photodetector 40 can be located farther from the window 50f than the light-emitting end face 30e of the laser diode 30, as long as the level of reflected light required for monitoring is obtained (see FIG. 5).

[0032] As shown in FIG. 3, the frame 50 is bonded to the edge of the mounting surface 10a of the substrate 10 so as to surround the laser diode 30. The bottom end surface 50b of the frame 50 is bonded to the mounting surface 10a of the substrate 10. This bonding can be achieved through an inorganic material such as a metal, or a layer of an organic material. However, when using a laser diode that emits blue or green light, it is preferable to avoid using organic materials, considering the effect of dust collection by the laser light.

[0033] The upper end surface 50a of the frame 50 is bonded to the mounting surface 11a of the substrate 11, similar to the substrate 10. The frame 50 defines a space V that accommodates the laser diode 30 and the photodetector 40. The substrate 11 functions as a cap, and the laser diode 30 and the photodetector 40 are mounted on the frame 50. are airtightly sealed in the space V. By airtightly sealing, the influence of dust collection by the laser light can be suppressed. However, airtight sealing is not essential.

[0034] In this way, by mounting the laser diode 30 and the photodetector 40 on different mounting surfaces 10a, 11a of a pair of substrates 10, 11, respectively, and by arranging the laser diode 30 and the photodetector 40 inside the same space V, the wiring can be divided and provided on each of the substrates 10, 11, making it possible to miniaturize the light source device 100.

[0035] As shown in FIG. 2 , the frame 50 has a window 50f that transmits a portion of the laser beam 14 emitted from the laser diode 30 and reflects a portion of the laser beam 14. The window 50f is disposed on the substrate 10 at a position across the laser beam 14. The window 50f has an incident surface 50c onto which the laser beam 14 emitted from the laser diode 30 enters and an exit surface 50d from which the laser beam 14 emitted from the laser diode 30 exits. The window 50f may be formed from a light-transmitting material such as glass, sapphire, or a transparent ceramic material, and may contain a phosphor. The portions of the frame 50 other than the window 50f may be formed from, for example, silicon, glass, ceramic, or the same material as the substrate described above.

[0036] In this embodiment, a protective element 60 is provided on the substrate 10. An example of the protective element 60 is a Zener diode. The protective element 60 is electrically connected in parallel to the laser diode 30 and functions as a protective circuit that suppresses the reverse voltage that may be applied to the laser diode 30 to a predetermined level or less. The protective element 60 is mounted on a pair of electrode pads pd formed on the mounting surface 10a of the substrate 10. In the example of FIG. 3, the p-side electrode of the laser diode 30 is electrically connected to the electrode pad pd on the mounting surface 20a. The anode sides of the pair of electrode pads pd on the mounting surface 10a of the substrate 10 are electrically connected to the electrode pad pd on the mounting surface 20a via conductive wires w. The cathode sides of the pair of electrode pads pd are electrically connected to the n-side electrode of the laser diode 30 via conductive wires w. In this manner, the protective element 60 can be electrically connected in parallel to the laser diode 30.

[0037] The laser light 14 reflected by the window 50f will be described in detail with reference to Figure 2. Figure 2 shows how monitor light enters the photodetector 40. The laser light 14 reflected by the entrance surface 50c and the exit surface 50d of the window 50f is shown schematically by representative light rays. Although the actual light rays are refracted at the interface between the window 50f and the air, for simplicity, the refraction is not shown in Figure 2 and other accompanying drawings.

[0038] When the laser light 14 emitted from the laser diode 30 enters the incident surface 50c of the window portion 50f, it passes through a first interface between the gas and the solid. The first interface corresponds to the incident surface 50c. The "gas" refers to air or an inert gas present inside the space V. The "solid" refers to the glass constituting the window portion 50f, for example. The refractive index of a gas such as air is approximately 1.0, while the refractive index of glass is, for example, 1.4 or higher. Therefore, the first interface is an interface between a dielectric material with a relatively low refractive index (air) and a dielectric material with a relatively high refractive index (glass). As a result, a so-called "fixed-end reflection" occurs, and a portion of the laser light 14 is reflected.

[0039] When the laser light 14 passes through the interior of the window portion 50f and is emitted from the emission surface 50d, it passes through a second interface that exists between the solid and the gas. The second interface corresponds to the emission surface 50d. The second interface is an interface between a dielectric material with a relatively high refractive index (e.g., glass) and a dielectric material with a relatively low refractive index (e.g., air). At the second interface, so-called "free-end reflection" also occurs, and a portion of the laser light 14 is reflected.

[0040] Thus, the proportion of laser light 14 emitted from laser diode 30 that is reflected by window 50f is determined by the reflectance of entrance surface 50c and exit surface 50d of window 50f. The reflectance of entrance surface 50c and exit surface 50d, i.e., the reflectance at the first and second interfaces, can be adjusted by an optical film composed of, for example, a single dielectric layer or multiple laminated dielectric layers, as described below. Because reflectance depends on the wavelength of light, the term "reflectance" in this disclosure refers to the reflectance at the peak wavelength of laser light 14 emitted from laser diode 30.

[0041] As described above, the laser beam 14 emitted from the laser diode 30 has a spreading property and forms an elliptical FFP on a plane parallel to the emission end surface 30e of the laser beam 14. The major axis of the ellipse is parallel to the stacking direction of the laser diode 30, and in the example of FIG. 2, the major axis of the ellipse is oriented in the Y-axis direction. Therefore, a portion of the laser beam emitted from the laser diode 30 and spreading upward (in the positive direction of the Y-axis) with respect to the central axis of the laser beam is reflected by the incident surface 50c of the window 50f, and a portion of the reflected light reaches the photodetector 40 without being blocked by the submount 20 and the laser diode 30. Similarly, a portion of the laser beam emitted from the laser diode 30 and spreading upward with respect to the central axis of the laser beam passes through the window 50f and is reflected by the emission surface 50d, and a portion of the reflected light reaches the photodetector 40 without being blocked by the submount 20 and the laser diode 30. A portion of the laser light 14 emitted from the laser diode 30 passes through the window 50f and is emitted to the outside. In this embodiment, by arranging the photodetector 40 directly above the laser diode 30, the laser light 14 emitted from the laser diode 30 is prevented from directly entering the light-receiving unit 40r. Instead, the light reflected by the window 50f can be made to enter the light-receiving unit 40r.

[0042] The higher the reflectance of the entrance surface 50c and the exit surface 50d of the window portion 50f, the higher the intensity of the laser light incident on the light-receiving portion 40r of the photodetector 40. However, the lower the reflectance of the entrance surface 50c and the exit surface 50d of the window portion 50f, the higher the light intensity of the laser light extracted from the light source device 100 and used. Therefore, the reflectance of the entrance surface 50c and the exit surface 50d of the window portion 50f can be adjusted so as to achieve a sufficiently high light intensity of the laser light 14 while enabling monitoring at a required level.

[0043] The reflectance of each of the entrance surface 50c and the exit surface 50d of the window portion 50f is preferably, for example, 1% to 10% with respect to the peak wavelength of the light to be reflected. In other words, the light transmittance of each of the entrance surface 50c and the exit surface 50d is preferably, for example, 90% to 99%.

[0044] Referring to Fig. 5, a configuration example of the light source device 100 in which the reflectances of the entrance surface 50c and the exit surface 50d of the window portion 50f are adjusted will be described. Fig. 5 is a cross-sectional view parallel to the YZ plane of another configuration example of the light source device 100 according to this embodiment. A reflectance adjustment portion can be formed on at least one of the entrance surface 50c and the exit surface 50d of the window portion 50f. The reflectance adjustment portion makes it possible to adjust the amount of laser light 14 emitted from the laser diode 30 and the amount of light required for monitoring by the photodetector 40.

[0045] In the example of FIG. 5, a reflectance adjusting section 55a is formed on the incident surface 50c, and a reflectance adjusting section 55b is formed on the exit surface 50d. Each of the reflectance adjusting sections 55a and 55b can be, for example, a single dielectric layer or a dielectric multilayer film composed of multiple laminated dielectric layers. The reflectance adjusting sections 55a and 55b each have a configuration similar to that of an optical film called an "anti-reflection film." However, a typical anti-reflection film has an extremely low reflectance, for example, a reflectance of 0.5% or less, so as to suppress reflection as much as possible. In contrast, in the embodiment of the present disclosure, it is necessary to obtain a level of reflected light required for monitoring from at least one of the first and second interfaces. This Therefore, the reflectance of the reflectance adjusting section 55a and the reflectance adjusting section 55b as a whole including both of them is determined to be in the range of, for example, 1% to 10%.

[0046] By changing the film thickness and material of the reflectance adjusting section, it is possible to control the reflectance of the reflective surface. This means that the amount of monitor light can be controlled. For example, when using a laser diode with an average output of 500 mW, setting the reflectance of the reflectance adjusting section to 1% will result in monitor light of 5 mW or less. Alternatively, when using a laser diode with an average output of 100 mW, setting the reflectance of the reflectance adjusting section to 5% will result in monitor light of 5 mW or less. In this way, by adjusting the reflectance of the reflectance adjusting section, it is possible to obtain monitor light of a desired intensity for laser light of any intensity. Furthermore, by reducing the amount of light reflected by the window portion 50f, it is possible to suppress a decrease in the amount of light output to the outside. As a result, it is possible to detect the monitor light with high accuracy while maintaining high output.

[0047] In one embodiment, the reflectance of the reflectance-adjusting portion 55a is higher than the reflectance of the reflectance-adjusting portion 55b. In this case, as long as the laser light 14s reflected by the reflectance-adjusting portion 55a can provide the light detector 40 with the amount of light required for monitoring, the reflectance of the reflectance-adjusting portion 55b may have a reflectance of 0.5% or less, like a general anti-reflection film. Therefore, the reflectance-adjusting portion 55b with such a low reflectance can be formed in the same manner as a general "anti-reflection film."

[0048] In another embodiment, the reflectivity of the reflectivity-adjusting portion 55b is higher than that of the reflectivity-adjusting portion 55a. In this case, as long as the laser beam 14t reflected by the reflectivity-adjusting portion 55b can provide the photodetector 40 with the amount of light required for monitoring, the reflectivity of the reflectivity-adjusting portion 55a may have a reflectivity of 0.5% or less, as with a general anti-reflection film. Therefore, the reflectivity-adjusting portion 55a with such a low reflectivity can be formed in the same manner as a typical "anti-reflection film." Adjusting the reflectivity of the incident surface 50c, which is one of the incident surface 50c and the exit surface 50d, to a low reflectivity advantageously reduces the amount of light returning to the laser diode. Furthermore, the distance from the exit surface 50d to the photodetector 40 is longer by the width of the window portion 50f than the distance from the incident surface 50c to the photodetector 40. Therefore, the laser beam 14t reflected by the reflectivity-adjusting portion 55b, which has a relatively high reflectivity, is more likely to reach the photodetector 40.

[0049] In this way, one of the reflectance-adjusting portions 55a and 55b may have an extremely low reflectance, similar to a conventional anti-reflection coating. Also, if the sensitivity of the photodetector 40 is high or if the reflected light efficiently enters the light-receiving portion 40r of the photodetector 40, both the reflectance-adjusting portion 55a and the reflectance-adjusting portion 55b may have an extremely low reflectance, similar to a conventional anti-reflection coating.

[0050] Furthermore, the reflectance adjusting portions 55a and 55b do not necessarily have to be in the form of a film. A fine uneven structure with a size shorter than the wavelength, such as a nanoparticle powder layer or a moth-eye structure, may be formed on the incident surface 50c and / or the exit surface 50d. Alternatively, the reflectance can be adjusted by modifying the surface of the incident surface 50c and / or the exit surface 50d to form a region on the glass surface with a lower refractive index than the interior. The reflectance adjusting portions 55a and 55b can also be realized by the modified region formed on the glass surface in this way. Furthermore, various configurations capable of adjusting the reflectance described above may be combined. The reflectance adjusting portions 55a and 55b may be selectively formed in the region through which the laser light 14 passes, or may be formed to extend to other regions depending on the manufacturing process.

[0051] Hereinafter, with reference to FIG. 6, an example of a configuration for reducing noise in monitoring by the photodetector 40 will be described.

[0052] FIG. 6 is a cross-sectional view parallel to the YZ plane of yet another configuration example of the light source device 100 according to this embodiment. The light source device 100 may further include a polarizer 70. The polarizer 70 may be disposed on the optical path between the window 50f and the photodetector 40. In the example of FIG. 6, the polarizer 70 is disposed in front of the light-receiving unit 40r of the photodetector 40. Because the relatively weak non-laser light emitted in all directions from the laser diode 30 is unpolarized, the intensity can be halved using the polarizer 70. As a result, the amount of non-laser light incident on the light-receiving unit 40r can be reduced, thereby reducing monitoring noise by the photodetector 40. The polarization transmission axis of the polarizer 70 is aligned with the polarization direction of the laser light 14 emitted from the laser diode 30. The reflected light of the laser light 14 emitted from the laser diode 30 and reflected by the window 50f enters the polarizer 70 while maintaining its polarization state. Therefore, such reflected light passes through the polarizer 70 and is appropriately detected by the photodetector 40.

[0053] With reference to FIGS. 7 to 10, several representative modifications of the light source device 100 according to this embodiment will be described.

[0054] 7 to 10 are cross-sectional views parallel to the YZ plane of modified examples of the light source device 100 according to this embodiment. Each of the drawings schematically shows the central axis of the laser light emitted from the laser diode 30. In these modified examples, at least one of the entrance surface 50c and the exit surface 50d of the window portion 50f intersects with the optical axis (i.e., the central axis) of the laser light 14 emitted from the laser diode 30 at an angle other than 90°.

[0055] In the example of FIG. 7, the window portion 50f is inclined from the normal direction (direction parallel to the Y-axis) of the mounting surface 10a of the substrate 10. The rear surface portion 50h of the frame 50, which is located on the opposite side of the window portion 50f with respect to the laser diode 30, is not inclined. As shown in FIG. 7, the inclination angles of the incident surface 50c and the emitting surface 50d are defined as θ1 and θ2, respectively. θ1 and θ2 may be equal to or different from each other. In the example of FIG. 7, both θ1 and θ2 are smaller than 90°. Therefore, the incident surface 50c and the emitting surface 50d are not perpendicular to the optical axis of the laser light 14 emitted from the laser diode 30, i.e., they intersect at an angle other than 90°.

[0056] Since the incident surface 50c and the exit surface 50d are inclined, it is easy to direct the light reflected by the inclined surfaces toward the photodetector 40. As a result, the return light to the laser diode 30 can be appropriately reduced.

[0057] The central axis of the light reflected by the window 50f can also change depending on the inclination angles of the incident surface 50c and the exit surface 50d. By adjusting the inclination angles of the incident surface 50c and / or the exit surface 50d of the window 50f so that more light reflected by the incident surface 50c and / or the exit surface 50d reaches the photodetector 40, a sufficient amount of light required for monitoring can be obtained. As a result, the detection accuracy of the photodetector 40 can be improved. In this case, a decrease in the amount of received light can also be suppressed by adjusting the position and angle of the light-receiving portion 40r of the photodetector 40 as necessary.

[0058] As shown in the example of FIG. 2, when the window portion 50f is not tilted, the light passing through the central axis of the laser beam 14 passes through the window portion 50f and is emitted to the outside. In contrast, as shown in the example of FIG. 7, by tilting at least one of the entrance surface 50c and the exit surface 50d of the window portion 50f, a portion of the light passing through the central axis of the laser beam 14 can be reflected by the window portion 50f and reach the photodetector 40. Compared to the light passing through the central axis of the laser beam 14, the output of the light passing through the periphery of the beam cross section tends to change more easily depending on the laser output, etc., especially the closer to the base. Therefore, by tilting the window portion 50f, the light passing through the central axis of the laser beam 14 can be reflected by the window portion 50f and reach the photodetector 40. A part of the light can be directed to the photodetector 40. This is very advantageous in terms of improving the detection accuracy of the monitor light.

[0059] In the example of FIG. 8, the rear surface 50h, like the window 50f, is inclined from the normal to the mounting surface 10a of the substrate 10. In the example of FIG. 9, only the exit surface 50d of the entrance surface 50c and the exit surface 50d of the window 50f is inclined at a predetermined inclination angle. In the example of FIG. 10, only the entrance surface 50c of the entrance surface 50c and the exit surface 50d of the window 50f is inclined at a predetermined inclination angle. In either configuration, adjusting the inclination angle of the entrance surface 50c or the exit surface 50d can provide a sufficient amount of light required for monitoring. Furthermore, by combining the adjustment of the inclination angle of the entrance surface 50c and / or the exit surface 50d with the reflectance adjustment unit described above, a desired level of reflected light can be obtained.

[0060] The light source device 100 in the embodiment of the present disclosure may include a plurality of laser diodes 30 and a plurality of photodetectors 40 .

[0061] An example of the configuration of a light source device 100 including a plurality of laser diodes 30 and a plurality of photodetectors 40 will be described with reference to Figs. 11 to 13A. Fig. 11 is a cross-sectional view parallel to the XY plane of a light source device 100 including a plurality of laser diodes 30 and a plurality of photodetectors 40 according to this embodiment. Fig. 12 is a perspective view schematically showing a plurality of laser diodes 30 fixed to a submount 20 on a substrate 10. Fig. 13A is a perspective view schematically showing a plurality of photodetectors 40 mounted on a substrate 11. Below, differences from the configuration of the light source devices already described will be mainly described.

[0062] In the example of FIG. 11, the light source device 100 includes multiple laser diodes 30 and multiple photodetectors 40. The multiple laser diodes 30 include a first laser diode 30a, a second laser diode 30b, and a third laser diode 30c. The multiple photodetectors 40 include a first photodetector 40a, a second photodetector 40b, and a third photodetector 40c. Hereinafter, the first laser diode, the second laser diode, and the third laser diode will each be simply referred to as "laser diodes," and the first photodetector, the second photodetector, and the third photodetector will each be simply referred to as "photodetectors." The three laser diodes 30a, 30b, and 30c and the three photodetectors 40a, 40b, and 40c can be hermetically sealed inside a space V.

[0063] The three laser diodes 30a, 30b, and 30c are mounted on the mounting surface 10a of the substrate 10 while being bonded to the submount 20. The spacing between two adjacent laser diodes in the example of FIG. 11 can be, for example, 50 μm or more and 2000 μm or less. The laser beams 14a, 14b, and 14c emitted from the laser diodes 30a, 30b, and 30c, respectively, enter the incident surface 50c of the window 50f, partially pass through the window 50f, and exit from the exit surface 50d, while partially are reflected by the window 50f. The laser beams 14a, 14b, and 14c emitted from the laser diodes 30a, 30b, and 30c, respectively, have different emission peak wavelengths. In this embodiment, the laser diode 30a emits red light, the laser diode 30b emits green light, and the laser diode 30c emits blue light. However, this is not limiting. According to this configuration example, a light source device is realized in which laser diodes of the three primary colors of RGB are mounted in one package.

[0064] The substrate 10 has a conductor wiring layer electrically connected to the three laser diodes 30a, 30b, and 30c. A plurality of protection elements 60 are provided on the mounting surface 10a of the substrate 10. The plurality of protection elements 60 include three protection elements 60a, 60b, and 60c. Each of the three protection elements 60a, 60b, and 60c is electrically connected to a pair of electrode pads pd formed on the mounting surface 10a. The protection element 60a is electrically connected to the laser diode 30a. The protection element 60b is electrically connected in parallel with the laser diode 30b, and the protection element 60c is electrically connected in parallel with the laser diode 30c.

[0065] The substrate 11 has a conductor wiring layer electrically connected to the three photodetectors 40a, 40b, and 40c. As shown in Fig. 13A, the three photodetectors 40a, 40b, and 40c are directly or indirectly supported on the mounting surface 11a of the substrate 11. Each of the three photodetectors 40a, 40b, and 40c is electrically bonded to a pair of electrode pads pd on the mounting surface 11a.

[0066] In the example of Figure 11, photodetector 40a is located directly above laser diode 30a. Photodetector 40a has a light receiving portion 40ar, and monitors the intensity of laser light 14a by receiving, at light receiving portion 40ar, part of laser light 14a emitted from laser diode 30a and reflected by window portion 50f. Photodetector 40b is located directly above laser diode 30b. Photodetector 40b has a light receiving portion 40br, and monitors the intensity of laser light 14b by receiving, at light receiving portion 40br, part of laser light 14b emitted from laser diode 30b and reflected by window portion 50f. Photodetector 40c is located directly above laser diode 30c. Photodetector 40c has a light receiving portion 40cr, and monitors the intensity of laser light 14c by receiving, at light receiving portion 40cr, part of laser light 14c emitted from laser diode 30c and reflected by window portion 50f. Photodetectors 40a, 40b, and 40c are located directly above laser diodes 30a, 30b, and 30c, respectively, to prevent direct incidence of laser beams 14a, 14b, and 14c. Furthermore, each photodetector can monitor the intensity of the corresponding laser beam, improving monitoring accuracy.

[0067] FIG. 13B is a perspective view that schematically illustrates a configuration in which multiple photodetectors are integrated and mounted on a substrate 11. As illustrated, instead of three independent photodetectors 40a, 40b, and 40c, a photodetector 41 can be used that implements the functions of those three independent photodetectors on a single chip. The photodetector 41 has light-receiving portions 40ar, 40br, and 40cr that receive laser beams 14a, 14b, and 14c, respectively. Compared to mounting individual photodetectors, using the photodetector 41 makes it possible to reduce the mounting space for the entire photodetector. This is advantageous for miniaturizing light source devices. [Industrial Applicability]

[0068] The light source device of the present disclosure can be suitably used as a light source for a head-mounted display, a projector, a lighting device, and the like. [Explanation of symbols]

[0069] 10: first substrate, 10a: first mounting surface, 11: second substrate, 11a: second mounting surface, 14a, 14b, 14c: laser light, 20: submount, 30, 30a: first laser diode, 30b: second laser diode, 30c: third laser diode, 40, 40a: first photodetector, 40b: second photodetector, 40c: third photodetector, 40ar, 40br, 40cr: light receiving section, 41: photodetector, 50: frame, 50c: incident surface, 50d: exit surface, 50f: window section, 55a, 55b: reflectance adjusting section, 60, 60a, 60b, 60c: protective element, 70: polarizer, 100: light source device, pd: electrode pad, w: conductive wire

Claims

1. a first substrate having a first mounting surface on which a first wiring layer is provided; a second substrate having a second mounting surface facing the first mounting surface and provided with a second wiring layer and an insulating portion; a first laser diode supported directly or indirectly on the first mounting surface and electrically connected to the first wiring layer; a first photodetector supported directly or indirectly on the second mounting surface and electrically connected to the second wiring layer; a frame defining a space for accommodating the first laser diode and the first photodetector; the first wiring layer is not exposed to the outside of the first substrate, and the second wiring layer is not exposed to the outside of the second substrate; the frame has a window portion and is joined to the first substrate and the second substrate; The window portion is tilted from a normal direction of the first mounting surface of the first substrate, a first laser diode having an incident surface on which the laser light emitted from the first laser diode is incident and an exit surface from which the laser light emitted from the first laser diode is exited, the first laser diode transmitting a portion of the laser light emitted from the first laser diode and reflecting a portion of the laser light emitted from the first laser diode; The first photodetector detects light reflected by the window portion out of the laser light emitted from the first laser diode.

2. The light source device according to claim 1 , wherein the first laser diode and the first photodetector are hermetically sealed within the space.

3. 3. The light source device according to claim 1, wherein the first photodetector at least partially overlaps the first laser diode when viewed in a direction perpendicular to the first mounting surface of the first substrate.

4. The light source device according to claim 1 , further comprising a submount bonded to the first mounting surface, the submount having the first laser diode disposed thereon.

5. The light source device according to claim 1 , wherein a reflectance adjusting portion is formed on at least one of the entrance surface and the exit surface of the window portion.

6. The light source device according to claim 1 , further comprising a polarizer disposed on an optical path between the window portion and the first photodetector.

7. 7. The light source device according to claim 6, wherein the polarization transmission axis of the polarizer is aligned with the polarization direction of the laser light emitted from the first laser diode.

8. 8. The light source device according to claim 1, wherein at least one of the entrance surface and the exit surface of the window portion intersects with the optical axis of the laser light emitted from the first laser diode at an angle other than 90°.

9. a second laser diode supported directly or indirectly on the first mounting surface; a third laser diode supported directly or indirectly on the first mounting surface; a second photodetector supported directly or indirectly on the second mounting surface; a third photodetector supported directly or indirectly on the second mounting surface; Furthermore, laser light emitted from the second laser diode and the third laser diode is incident on the incident surface, a part of the laser light passes through the window portion and is emitted from the exit surface, and a part of the laser light is reflected by the window portion, the second photodetector detects light reflected by the window portion out of the laser light emitted from the second laser diode; The light source device according to claim 1 , wherein the third photodetector detects light reflected by the window portion out of the laser light emitted from the third laser diode.

10. 10. The light source device according to claim 9, wherein the first laser diode, the second laser diode, the third laser diode, the first photodetector, the second photodetector, and the third photodetector are hermetically sealed within the space.

11. the first laser diode, the second laser diode, and the third laser diode are electrically connected to the first wiring layer; The light source device according to claim 9 , wherein the first photodetector, the second photodetector, and the third photodetector are electrically connected to the second wiring layer.

12. 12. The light source device according to claim 10, further comprising a submount bonded to the first mounting surface, on which the first laser diode, the second laser diode, and the third laser diode are arranged.

13. 13. The light source device according to claim 9, wherein the first laser diode, the second laser diode, and the third laser diode emit laser beams having emission peak wavelengths different from one another.

Images