Light-emitting device

Abstract

To provide a light-emitting device that achieves a light emitting point pitch and a light-emitting position which a single LD cannot accomplish and that can attain a reduction in size.SOLUTION: A light-emitting device of the present disclosure comprises: a plurality of LDs arranged along a predetermined direction; a planar lightwave circuit having a plurality of optical waveguides; and a lens on which light beams emitted from the plurality of optical waveguides are incident. The plurality of optical waveguides include: a first optical waveguide that makes first light emitted from the first LD incident on a first light incidence end and emits that from a first light emission end; and a second optical waveguide that makes second light emitted from the second LD incident on a second light incidence end and emits that from a second light emission end. The first light emission end refracts and emits the first light toward a first direction which inclines relative to a direction normal to the first light emission end. The second light emission end refracts and emits the second light toward a second direction which inclines relative to a direction normal to the second light emission end. A first distance from the first light emission end to a lens surface in the first direction is shorter than a second distance from the second light emission end to the lens surface in the second direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The applications of light-emitting devices equipped with laser diodes (semiconductor laser elements) are expanding to various fields. Patent Document 1 describes an apparatus that modulates laser light emitted from multiple laser diodes using an optical waveguide array and records it on a photosensitive material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-189705 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a light emitting device that can be miniaturized and realizes a light emitting point pitch and light emitting position that cannot be achieved by a laser diode (LD) alone. [Means for solving the problem]

[0005] In an exemplary embodiment, the light emitting device of the present disclosure includes a plurality of laser diodes arranged along a predetermined direction, a planar lightwave circuit having a plurality of optical waveguides that respectively guide light emitted from the plurality of laser diodes, and a lens into which the light emitted from the plurality of optical waveguides is incident. The plurality of laser diodes include a first laser diode that oscillates at a first peak wavelength and a second laser diode that oscillates at a second peak wavelength longer than the first peak wavelength. The plurality of optical waveguides include a first optical waveguide that receives the first light emitted from the first laser diode from a first light input end and outputs it from a first light output end, and a second optical waveguide that receives the second light emitted from the second laser diode from a second light input end and outputs it from a second light output end. The center-to-center distance between the first light output end and the second light output end is shorter than the center-to-center distance between the first light input end and the second light input end. The first light emitting end refracts and emits the first light in a first direction inclined with respect to a normal direction of the first light emitting end. The second light emitting end refracts and emits the second light in a second direction inclined with respect to a normal direction of the second light emitting end. A first distance from the first light emitting end to a surface of the lens in the first direction is shorter than a second distance from the second light emitting end to the surface of the lens in the second direction. Effect of the Invention

[0006] According to the embodiments of the present disclosure, it is possible to provide a light emitting device that can be miniaturized and realizes a light emitting point pitch and light emitting position that cannot be achieved by a laser diode (LD) alone. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view illustrating a schematic configuration example of a light emitting device according to an embodiment of the present disclosure. [Figure 2A] FIG. 2A is a diagram showing a light incident surface of a Planar Lightwave Circuit (PLC) of the light emitting device of FIG. 1 as viewed from the negative side of the Y axis. [Figure 2B]FIG. 2B is a diagram showing the light exit surface of the PLC of the light emitting device of FIG. 1 as viewed from the positive side of the Y axis. [Diagram 3] FIG. 3 is a plan view that illustrates a state in which light is refracted and emitted from a plurality of light emitting ends of the PLC in the embodiment. [Figure 4] FIG. 4 is a plan view showing the relationship of distances from a plurality of light emitting ends of a PLC to the surface of a lens in the embodiment. [Diagram 5] FIG. 5 is a plan view showing another configuration example of the light emitting device according to the embodiment of the present disclosure. [Figure 6A] FIG. 6A is a diagram showing the light incident surface of the PLC of the light emitting device of FIG. 5 viewed from the negative side of the Y axis. [Figure 6B] FIG. 6B is a diagram showing the light exit surface of the PLC of the light emitting device of FIG. 5 as viewed from the positive side of the Y axis. [Figure 7] FIG. 7 is a plan view showing a portion of a modified example of a PLC according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a plan view showing a portion of another modified example of the PLC according to the embodiment of the present disclosure. [Figure 9] FIG. 9 is a plan view showing still another configuration example of the light emitting device according to the embodiment of the present disclosure. [Figure 10] FIG. 10 is a perspective view showing still another configuration example of the light emitting device according to the embodiment of the present disclosure. [Figure 11] FIG. 11 is a cross-sectional view that typically shows a cross section parallel to the YZ plane of the light emitting device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A basic configuration example of a light emitting device according to an embodiment of the present disclosure will be described with reference to Figures 1, 2A, 2B, and 3. For reference, the drawings show an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other.

[0009] First, refer to FIG. 1. FIG. 1 is a plan view showing a schematic configuration example of a light emitting device in this embodiment. The light emitting device 1000 shown in FIG. 1 includes a plurality of laser diodes 10 arranged along a predetermined direction (the X-axis direction in FIG. 1). In FIG. 1, the shapes and sizes of the plurality of laser diodes 10 are shown to be equal to each other, but the shapes or sizes may be different from each other. In the illustrated example, the plurality of laser diodes 10 include a first laser diode 10-1, a second laser diode 10-2, and a third laser diode 10-3. The number of laser diodes 10 is not limited to three, and may be two, or may be four or more. The first laser diode 10-1 oscillates at a first peak wavelength λ1. The second laser diode 10-2 oscillates at a second peak wavelength λ2 that is longer than the first peak wavelength λ1. The third laser diode 10-3 oscillates at a third peak wavelength λ3 that is longer than the second peak wavelength λ2. In this manner, in this embodiment, the laser diodes 10 each emit laser light having a different peak wavelength. Therefore, the light emitting device 1000 according to this embodiment can be called a "multi-wavelength light source." When such a multi-wavelength light source is used as a light source for a display device, the first peak wavelength λ1 can be in the range of, for example, 400 nm to 495 nm, the second peak wavelength λ2 can be in the range of, for example, 495 nm to 600 nm, and the third peak wavelength λ3 can be in the range of, for example, 600 nm to 750 nm.

[0010] The plurality of laser diodes 10 may include a fourth laser diode that oscillates at a fourth peak wavelength λ4 that is different from any of the first peak wavelength λ1, the second peak wavelength λ2, and the third peak wavelength λ3.

[0011] The first peak wavelength λ1, the second peak wavelength λ2, the third peak wavelength λ3, and the fourth peak wavelength λ4 may all be included in the visible light range, or any of the peak wavelengths may be outside the visible light range. For example, the fourth peak wavelength λ4 may be in the range of 780 nm to 2000 nm included in the infrared range. By setting the fourth peak wavelength λ4 in the infrared range, it can be used as a sensor and sensing can be performed without affecting the image.

[0012] The light emitting device 1000 further includes a planar lightwave circuit (PLC) 200 having a plurality of optical waveguides 20 that respectively guide the light emitted from the plurality of laser diodes 10, and a lens 30 into which the light emitted from the plurality of optical waveguides 20 is incident. A lens may be provided between the plurality of laser diodes 10 and the PLC 200. The configuration of each optical waveguide 20 is not particularly limited, and any configuration that functions as an optical waveguide may be adopted. For example, the PLC 200 includes a substrate, a waveguide core provided on the substrate, and a clad layer that covers the waveguide core. The substrate, the waveguide core, and the clad layer are formed of an inorganic material such as silicon or quartz, or an organic material such as plastic or resin. For example, when the substrate is formed of an inorganic material, the waveguide core and the clad layer are also formed of an inorganic material, and when the substrate is formed of a resin material, the waveguide core and the clad layer may also be formed of a resin material. When the waveguide core and cladding layers are formed from a polymer, examples of the polymer include PMMA (polymethyl methacrylate), polyimide resins, silicone resins, polystyrene resins, polycarbonate resins, polyamide resins, polyester resins, phenolic resins, polyquinoline resins, polyquinoxaline resins, polybenzoxazole resins, polybenzothiazole resins, and polybenzimidazole resins. Examples of the polyimide resins include polyimide resins, poly(imide-isoindoloquinazolinedionimide) resins, polyetherimide resins, polyetherketone resins, and polyesterimide resins.

[0013] The waveguide core is made of a material having a higher refractive index than the surrounding material, and can exhibit a light trapping effect. The light emitted from each of the optical waveguides 20 spreads at a predetermined angle and travels in the direction of the dashed lines shown in FIG.

[0014] The lens 30 is, for example, a collimator lens. The lens 30 has a lens surface that reduces the spread angle (divergence angle) of the light emitted from the multiple optical waveguides 20 of the PLC 200 by refraction. Such a lens surface is formed on at least one of the entrance side and exit side of the lens 30. The shape of the lens surface is not limited to a spherical surface, and may be aspherical. The light transmitted through the lens 30 does not need to form a strictly parallel beam, and may be configured to converge or diverge in combination with another optical system. In the example shown in the figure, the optical axis direction 32 of the lens 30 is inclined, for example, in a range of 25 degrees to 85 degrees with respect to a predetermined direction (X-axis direction) in which the laser diodes 10 are arranged. In addition, the lens 30 preferably has a numerical aperture (NA) of 0.1 to 0.7, preferably 0.2 to 0.6, and a focal length of 0.5 mm to 10 mm, preferably 1 mm to 5 mm.

[0015] Light beams with different peak wavelengths emitted from the multiple optical waveguides 20 overlap each other and enter the lens 30. When the focal length of the lens 30 (when the wavelength of the light is 455 nm) is, for example, 3 mm, the beam diameter (diameter) of the light entering the lens 30 can be, for example, 0.9 mm or more and 5 mm or less at the position of the surface 30S of the lens 30. The surface 30S of the lens 30 does not need to be a curved surface that functions as a lens surface, and may be a flat surface.

[0016] In this embodiment, the multiple optical waveguides 20 of the PLC 200 include a first optical waveguide 20-1, a second optical waveguide 20-2, and a third optical waveguide 20-3. The first optical waveguide 20-1 receives the first light emitted from the first laser diode 10-1 through a first light input end 22-1 and outputs it from a first light output end 24-1. The second optical waveguide 20-2 receives the second light emitted from the second laser diode 10-2 through a second light input end 22-2 and outputs it from a second light output end 24-2. The third optical waveguide 20-3 receives the third light emitted from the third laser diode 10-3 through a third light input end 22-3 and outputs it from a third light output end 24-3. When a fourth laser diode is further included, the multiple optical waveguides 20 may further include a fourth optical waveguide into which the fourth light emitted from the fourth laser diode is incident from a fourth light input end and which emits the fourth light from a fourth light output end. The first to fourth lights are preferably incident perpendicularly to the first to fourth light input ends, but do not have to be incident perpendicularly.

[0017] The PLC 200 has a light incident surface 220 including a first light incident end 22-1, a second light incident end 22-2, and a third light incident end 22-3. The PLC 200 also has a light exit surface 240 including a first light exit end 24-1, a second light exit end 24-2, and a third light exit end 24-3. In this embodiment, the light incident surface 220 and the light exit surface 240 of the PLC 200 both extend linearly in a plan view. As shown in FIG. 1, the normal direction N1 of the light exit surface 240 of the PLC 200 is inclined with respect to the optical axis direction 32 of the lens 30. In the illustrated example, the normal direction N1 of the light exit surface 240 in the PLC 200 is also inclined with respect to the normal direction N2 of the light incident surface 220. In other words, the light incident surface 220 and the light exit surface 240 of the PLC 200 are in a non-parallel relationship. In the present disclosure, two directions being "inclined" means that the angle between the two directions is in the range of 5 degrees or more and 85 degrees or less.

[0018] Next, reference is made to FIG. 2A and FIG. 2B. FIG. 2A is a diagram showing a light incident surface 220 of the PLC 200 viewed from the negative side of the Y axis. FIG. 2B is a diagram showing a light exit surface 240 of the PLC 200 viewed from the positive side of the Y axis. In the illustrated example, the PLC 200 has a substrate 25, a plurality of waveguide cores 26 provided on the substrate 25, and a clad layer 27 covering the plurality of waveguide cores 26. The substrate 25 may have an underclad layer on its surface. The clad layer 27 covering the waveguide cores 26 functions as an overclad layer. The thickness of each of the underclad layer and the overclad layer is, for example, in the range of 10 μm to 100 μm. The height (thickness) and width of the waveguide cores 26 are, for example, in the range of about 1 μm to 10 μm. The cross section of each of the waveguide cores 26 perpendicular to the waveguiding direction has a roughly rectangular shape. This cross section may have a circular or elliptical shape. The size of the waveguide core 26 is larger when waveguiding is performed in multimode than when waveguiding is performed in single mode. In this embodiment, the size of the waveguide core 26 is selected so that waveguiding is performed in single mode. For example, when the wavelength of light is 455 nm, the height and width of the waveguide core 26 can be both 1 μm or more and 3 μm or less.

[0019] As can be seen from Figures 2A and 2B, the center distance between the first light emitting end 24-1 and the second light emitting end 24-2 is shorter than the center distance between the first light input end 22-1 and the second light input end 22-2, and the center distance between the second light emitting end 24-2 and the third light emitting end 24-3 is shorter than the center distance between the second light input end 22-2 and the third light input end 22-3. The center distance between adjacent light emitting ends among the first light emitting end 24-1, the second light emitting end 24-2, and the third light emitting end 24-3 corresponds to the center distance between adjacent light emitting points on the light output surface 240 of the PLC 200. The center distance between the light emitting points may be, for example, in the range of 2 μm to 200 μm, and preferably in the range of 2 μm to 100 μm.

[0020] By using such a PLC200, the center-to-center distance of the light emitting points on the light emitting surface 240 of the PLC200 can be made smaller than the lower limit (e.g., 250 μm) of the center-to-center distance of the plurality of laser diodes 10, which is determined by the element size and the margin of mounting. By making the center-to-center distance of the light emitting points smaller, it is not necessary to use a plurality of lenses to collimate the light emitted from each light emitting point, and collimation by one lens is possible. This is because it is possible to arrange the plurality of light emitting points close to the optical axis of the lens. Also, in the example of FIG. 1, if no lens is provided between the plurality of laser diodes 10 and the light incident surface 220 of the PLC200, there is only a gap of, for example, 10 μm or less. For miniaturization, it is desirable to arrange the laser diode 10 close to the light incident surface 220 of the PLC200. Such a configuration is advantageous in that the head mounted display can be miniaturized when the light emitting device according to the present disclosure is used as a light source for a head mounted display or the like. The light emitting device according to the present disclosure can be mounted, for example, on the temple part of a glasses-like head mounted display. An optical element such as a microlens may be disposed between each laser diode 10 and the optical waveguide 20. Furthermore, when miniaturization of the light emitting device is not intended, the light emitted from each laser diode 10 may be coupled to the optical waveguide 20 by an optical fiber.

[0021] Next, FIG. 3 is referred to. FIG. 3 is a plan view showing a schematic view of the state in which light is refracted and emitted from the plurality of light emitting ends 24-1, 24-2, and 24-3 of the PLC 200 in this embodiment. In this embodiment, the first light emitting end 24-1 refracts the first light in a first direction 101 inclined with respect to the normal direction N11 of the first light emitting end 24-1 and emits it. The second light emitting end 24-2 refracts the second light in a second direction 102 inclined with respect to the normal direction N12 of the second light emitting end 24-2 and emits it. The third light emitting end 24-3 refracts the third light in a third direction 103 inclined with respect to the normal direction N13 of the third light emitting end 24-3 and emits it. In the example of FIG. 3, the normal directions N11, N12, and N13 are parallel to each other. Although it is desirable that the light exit surface 240 is a flat surface, the light exit surface 240 does not necessarily have to be a flat surface, and the normal directions N11, N12, and N13 may be at an angle of 10 degrees or less.

[0022] In the plan view of FIG. 3, the waveguiding direction of the first optical waveguide 20-1 is angled at a first angle θ i1 The waveguide direction of the second optical waveguide 20-2 intersects with the normal direction N12 of the second light emitting end 24-2 at a second angle θ i2 They intersect at the first angle θ i1 is the second angle θ i2 The waveguiding direction of the third optical waveguide 20-3 is angled at a third angle θ i3 and intersect at a second angle θ i2 is the third angle θ i3 The first angle θ i1 , second angle θ i2 , third angle θ i3 are all greater than 0 degrees and smaller than the angle of total reflection.

[0023] The light guided through the first optical waveguide 20-1 is refracted at the solid-air interface at the first light output end 24-1, thereby changing its propagation direction. Similarly, the light guided through the second optical waveguide 20-2 and the third optical waveguide 20-3 is refracted at the solid-air interface at the second light output end 24-2 and the third light output end 24-3, thereby changing its propagation direction.

[0024] The angle between the light emitted from the first light emitting end 24-1 and the normal direction N11 of the first light emitting end 24-1 is defined as θ o1 Similarly, the angle between the light emitted from the second light emitting end 24-2 and the normal direction N12 of the second light emitting end 24-2 is set as θ o2 The angle between the light emitted from the third light emitting end 24-3 and the normal direction N13 of the third light emitting end 24-3 is defined as θ o3 In this case, the following relationship holds according to Snell's law: Sin θ o1 = (sin θ i1 )n i(λ1) / n o Sin θ o2 = (sin θ i2 )n i(λ2) / n o Sin θ o3 = (sin θ i3 )n i(λ2) / n o where n i(λ) is the refractive index of the optical waveguide 20 at the wavelength λ (for example, 1.4 to 2.0), and n o is the refractive index of the material on the gas side (typically air). The optical waveguides 20 do not need to be made of the same material. If they are made of the same material, the wavelengths of light guided through each optical waveguide 20 are different, so the refractive index n i(λ) depends on the wavelength. If the material has normal dispersion, then λ1<λ2<λ3, so n i(λ1) >n i(λ2) >n i(λ3) In such a case, in this embodiment, θ i1 <θ i2 <θ i3 Therefore, θ o1 , θ o2 , θ o3 In addition, when the material of the optical waveguide 20 does not have wavelength dispersion or when the wavelength dispersion can be ignored, θ i1 , θ i2 , θ i3have equal magnitudes, then θ o1 , θ o2 , θ o3 will also have equal magnitude to each other.

[0025] In this way, θ i1 , θ i2 , θ i3 By adjusting θ o1 , θ o2 , θ o3 In other words, the directions of the light emitted from each of the first light emitting end 24-1, the second light emitting end 24-2, and the third light emitting end 24-3 can be controlled. In the example of Fig. 3, the first direction 101, the second direction 102, and the third direction are parallel to each other and point in the same direction.

[0026] Next, reference is made to Fig. 4. Fig. 4 is a plan view showing the relationship of distances from a plurality of light emitting ends of a PLC to a surface 30S of a lens 30 in the embodiment.

[0027] As shown in FIG. 4, according to the configuration of this embodiment, the first distance L1 from the first light emitting end 24-1 to the surface 30S of the lens 30 in the first direction 101 is shorter than the second distance L2 from the second light emitting end 24-2 to the surface 30S of the lens 30 in the second direction 102. Also, the second distance L2 from the second light emitting end 24-2 to the surface 30S of the lens 30 in the second direction 102 is shorter than the third distance L3 from the third light emitting end 24-3 to the surface 30S of the lens 30 in the third direction 103. In the illustrated example, the focal length of the lens 30 has different values ​​depending on the wavelength λ of light. In the illustrated example, the shorter the wavelength λ of light, the shorter the focal length of the lens 30. According to this embodiment, the optical axis direction 32 of the lens 30 is not parallel to the normal direction N1 of the light emitting surface 240, but is inclined. In other words, the optical axis direction 32 of the lens 30 is inclined with respect to the light emitting surface 240.

[0028] Here, the angle of the optical axis direction 32 of the lens 30 with respect to the light exit surface 240 is θ. If the first direction 101 and the second direction 102 are substantially parallel, L2-L1 is approximately equal to the distance obtained by multiplying the center-to-center distance between the first light exit end 24-1 and the second light exit end 24-2 by cos θ. Similarly, if the second direction 102 and the third direction 103 are substantially parallel, L3-L2 is approximately equal to the distance obtained by multiplying the center-to-center distance between the second light exit end 24-2 and the third light exit end 24-3 by cos θ.

[0029] As is clear from the above, by adjusting the center distance and the angle θ between the adjacent light emitting ends 24, it is possible to match the distances L1, L2, and L3 to the focal length suitable for the wavelength of each light. As described above, the light emitting point pitch of the PLC 200 can be reduced to 200 μm or less. However, in order to appropriately set the distances L1, L2, and L3 according to the focal length of the lens 30, it is necessary to appropriately adjust the distances indicated by L2-L1 and L3-L2, and the light emitting point pitch can also be adjusted. In some cases, the light emitting point pitch can be set to a value exceeding 200 μm.

[0030] In the above description, for simplicity, the number of laser diodes 10 is three. Below, an example in which the number of laser diodes 10 is six will be described.

[0031] 5 is a plan view showing another configuration example of the light emitting device 2000 according to an embodiment of the present disclosure. The basic configuration of the light emitting device 2000 is similar to the basic configuration of the light emitting device 1000 described above.

[0032] The light emitting device 2000 in this embodiment includes six laser diodes 10 arranged along a predetermined direction (X-axis direction). In the illustrated example, the six laser diodes 10 include a first laser diode 10-1, a second laser diode 10-2, a third laser diode 10-3, a fourth laser diode 10-4, a fifth laser diode 10-5, and a sixth laser diode 10-6. Hereinafter, the reference symbols of these laser diodes may be represented as "10-N", where "N" is an integer equal to or greater than 1. The peak wavelength of the oscillation of the laser diode 10-N is represented as "λN".

[0033] In the light emitting device 2000, the relationship of the peak oscillation wavelength is λ1<λ2<λ3<λ4<λ5<λ6. For example, a laser diode that emits blue light, a laser diode that emits green light, or a laser diode that emits red light may be used as the laser diode 10. A laser diode that emits light other than blue, green, and red, such as ultraviolet or infrared light, may also be used.

[0034] 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.

[0035] 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. Laser diodes that emit red light include those that include InAlGaP, GaInP, GaAs, and AlGaAs semiconductors.

[0036] In the light emitting device 2000 of this embodiment, for example, λ1 is in the range of 420 nm to 494 nm, λ2 and λ3 are in the range of 495 nm to 570 nm, and λ4, λ5 and λ6 are in the range of 605 nm to 750 nm. In other words, blue, green and red light containing two types of light components with different peak wavelengths may be emitted from the laser diode 10.

[0037] The light emitting device 2000 further includes a PLC 200 having a plurality of optical waveguides 20-N that guide the light emitted from the plurality of laser diodes 10-N, respectively, and a lens 30 into which the light emitted from the plurality of optical waveguides 20-N is incident. The configurations of the optical waveguides 20 and the lens 30 are as described above, and therefore will not be described here.

[0038] Fig. 6A is a diagram showing light incident surface 220 when PLC 200 is viewed from the negative side of the Y axis. Fig. 6B is a diagram showing light exit surface 240 when PLC 200 is viewed from the positive side of the Y axis. At least one of light incident surface 220 and light exit surface 240 may be provided with a protective film or an anti-reflection film.

[0039] In this example, the Nth optical waveguide 20-N receives the Nth light emitted from the Nth laser diode 10-N through the Nth light incident end 22-N and emits the Nth light from the Nth light emitting end 24-N. The light emitted from the N light emitting ends 24 is preferably directed in a direction parallel to the optical axis direction 32 of the lens 30.

[0040] According to this embodiment, even when laser light is emitted from six light emitting points, the light emitting points can be contained in a narrow range. In addition, for multi-wavelength laser light having different peak wavelengths over a wide range of the visible light region, each light emitting point can be collected near the focal position of the lens 30. In this embodiment, an offset of 5 μm to 100 μm can be provided between the distance from the first light emitting end 24-1 to the surface 30S of the lens 30 and the distance from the sixth light emitting end 24-6 to the surface 30S of the lens 30 according to the difference in focal length caused by the difference in peak wavelength. As a result, it is possible to suitably collimate laser beams of different colors by the same lens 30.

[0041] In this light emitting device 2000, the relationship of the oscillation peak wavelengths is λ1<λ2<λ3<λ4<λ5<λ6, but it is not necessary for all the laser diodes 10 to have different oscillation wavelengths. For example, the relationship of λ1<λ2=λ3<λ4=λ5=λ6 may be satisfied. In this case, the laser diodes 10-1 and 10-2 emit blue light. The laser diodes 10-3 and 10-4 emit green light, and the laser diodes 10-5 and 10-6 emit red light. The multiple laser diodes 10 may include a laser diode that emits infrared light.

[0042] FIG. 7 is a plan view showing a part of a modified example of the PLC 200. The light emitting surface 240 of the PLC 200 may have one or more steps in a plan view. In the example of FIG. 7, the light emitting surface 240 has a step S1 and a step S2 in the illustrated range. The steps S1 and S2 are formed by offsetting a part of the light emitting surface 240 in the optical axis direction 32 of the lens 30. Since the step S1 exists between the first light emitting end 24-1 and the second light emitting end 24-2, the distance from the second light emitting end 24-2 to the surface 30S of the lens 30 can be further longer than the distance from the first light emitting end 24-1 to the surface 30S of the lens 30. The offset amount in the optical axis direction 32 of the lens 30 formed by each of the steps S1 and S2 is, for example, in the range of 5 μm to 100 μm.

[0043] In the example of FIG. 7, the normal direction N11 of the first light emitting end 24-1 and the normal direction N12 of the second light emitting end 24-2 are parallel to each other, but in the embodiment of the present disclosure, the normal directions N11 and N12 do not need to be parallel to each other. In addition, the directions 101 and 102 of the light emitted from each light emitting end 24-1 and 24-2 do not need to be parallel to the optical axis direction 32 of the lens 30. As long as each light emitting point (the center of the light emitting end 24-N) is located at a position close to the focal position of the lens 30, even if the directions of the light emitted from each light emitting point are different, the light emitted from each light emitting point can be appropriately collimated as long as it enters the range of the effective diameter of the lens 30. This is because the lens has a function of approximately parallelizing a bundle of light rays emanating from a light emitting point at the focal position. Therefore, as long as the center distance between the light emitting ends 24-1, 24-2, and 24-3 is shortened and each light emitting point is close to the focal position according to the respective color of the lens 30, the first direction 101, the second direction 102, and the third direction 103 do not need to be the same direction.

[0044] 8 is a plan view showing a part of another modified example of the PLC 200. The light emitting surface 240 of this PLC 200 is composed of a plurality of planar regions so that the normal direction N1n of the n-th light emitting end 24-n faces different directions. In the example of FIG. 8, since the second light emitting end 24-2 is inclined with respect to the first light emitting end 24-1, the distance from the second light emitting end 24-2 to the surface 30S of the lens 30 can be made longer than the distance from the first light emitting end 24-1 to the surface 30S of the lens 30. Similarly, since the third light emitting end 24-3 is inclined with respect to the second light emitting end 24-2, the distance from the third light emitting end 24-3 to the surface 30S of the lens 30 can be made longer than the distance from the second light emitting end 24-2 to the surface 30S of the lens 30.

[0045] Fig. 9 is a plan view showing yet another configuration example of a light emitting device according to an embodiment of the present disclosure. In the example of Fig. 9, a normal direction N1 of the light emitting surface 240 of the PLC 200 and a normal direction N2 of the light incident surface 220 are parallel to each other. In this embodiment, a rectangular substrate can be used as the substrate of the PLC 200. The shape and size of the PLC 200 in plan view are arbitrary.

[0046] The light emitting device according to any of the above embodiments may include a package that encapsulates the multiple laser diodes 10 and the PLC 200.

[0047] FIG. 10 is a perspective view showing an example of a light emitting device 4000 having a package structure that seals a plurality of laser diodes 10, a PLC 200, and a lens 30 inside. FIG. 11 is a diagram showing a schematic cross section parallel to the YZ plane of the light emitting device 4000 in FIG. 10. The light emitting device 4000 includes a support substrate 14 that supports a plurality of laser diodes 10, a PLC 200, and a lens 30, and a cap member 16 that covers the plurality of laser diodes 10, a PLC 200, and a lens 30. The support substrate 14 and the cap member 16 function as a package that hermetically seals the laser diodes 10, the PLC 200, and the lens 30 housed therein. More specifically, the cap member 16 has a wall surface portion 16W that is bonded to the support substrate 14, and a top surface portion 16T that faces the support substrate 14. The wall surface portion 16W of the cap member 16 surrounds the plurality of laser diodes 10, the PLC 200, and the lens 30 on the support substrate 14. A part or the whole of the wall portion 16W is formed from a light-transmitting material that transmits the light collimated or converged by the lens 30, and enables the light that has transmitted through the lens 30 to be emitted to the outside from the light-emitting device 4000.

[0048] 10 and 11, a plurality of laser diodes 10 are supported by a submount 18. The thickness of the submount 18 can be determined so that the light emitted from the laser diodes 10 can be appropriately incident on the light incident end of the PLC 200.

[0049] In the illustrated example, the number of laser diodes 10 is three, but the light emitting device 4000 may include four or more laser diodes 10. [Industrial Applicability]

[0050] The light emitting device according to the present disclosure can be suitably used as a light source for a head mounted display, a projector, or the like. [Explanation of symbols]

[0051] 10...laser diode, 20...optical waveguide, 25...substrate, 26...waveguide core, 27...cladding layer, 30...lens, 30S...lens surface, 32...lens optical axis direction, 101...first direction, 102...second direction, 103...third direction, 200...PLC, 220...light incident surface, 240...light exit surface, N1...normal direction of light exit surface, N2...normal direction of light incident surface

Claims

1. A plurality of laser diodes arranged in a predetermined direction; a planar lightwave circuit having a plurality of optical waveguides for guiding light beams emitted from the plurality of laser diodes, respectively; a lens into which the light emitted from the plurality of optical waveguides is incident; Equipped with the plurality of laser diodes include a first laser diode that oscillates at a first peak wavelength and a second laser diode that oscillates at a second peak wavelength that is longer than the first peak wavelength, the plurality of optical waveguides include a first optical waveguide into which a first light emitted from the first laser diode is incident from a first light input end and which emits the first light from a first light output end, and a second optical waveguide into which a second light emitted from the second laser diode is incident from a second light input end and which emits the second light from a second light output end, a center-to-center distance between the first light emitting end and the second light emitting end is shorter than a center-to-center distance between the first light incident end and the second light incident end; the first light emitting end refracts the first light in a first direction inclined with respect to a normal direction of the first light emitting end and emits the first light; the second light emitting end refracts the second light in a second direction inclined with respect to a normal direction of the second light emitting end and emits the second light; a first distance from the first light emitting end to a surface of the lens in the first direction is shorter than a second distance from the second light emitting end to the surface of the lens in the second direction; In a plan view, a waveguiding direction of the first optical waveguide intersects with a normal direction of the first light emitting end at a first angle, and a waveguiding direction of the second optical waveguide intersects with a normal direction of the second light emitting end at a second angle, the first angle being smaller than the second angle; a portion of the first optical waveguide connected to the first light emitting end and a portion of the second optical waveguide connected to the second light emitting end are non-parallel to each other.

2. The light emitting device according to claim 1 , wherein the first direction and the second direction are the same direction.

3. The planar lightwave circuit comprises: a light incident surface including the first light incident end and the second light incident end; a light emitting surface including the first light emitting end and the second light emitting end; The light emitting device according to claim 1 , wherein a normal direction of the light exit surface is inclined with respect to an optical axis direction of the lens.

4. The optical axis direction of the lens is inclined with respect to the predetermined direction. The light emitting device according to claim 1 .

5. The light emitting device according to claim 3 , wherein the light emitting surface of the planar lightwave circuit has one or more steps in a plan view.

6. The light emitting device according to claim 1 , wherein a center-to-center distance between the first light emitting end and the second light emitting end is not less than 2 μm and not more than 200 μm.

7. the plurality of laser diodes includes a third laser diode oscillating at a third peak wavelength longer than the second peak wavelength, the plurality of optical waveguides include a third optical waveguide into which the third light emitted from the third laser diode is incident from a third light input end and which emits the third light from a third light output end; a center-to-center distance between the second light output end and the third light output end is shorter than a center-to-center distance between the second light input end and the third light input end; the third light emitting end refracts the third light in a third direction inclined with respect to a normal direction of the third light emitting end and emits the third light, The light emitting device according to claim 1 , wherein the second distance is shorter than a third distance from the third light emitting end to a surface of the lens in the third direction.

8. The light emitting device according to claim 7 , wherein the first direction, the second direction, and the third direction are the same direction.

9. The light emitting device according to claim 7 , wherein the first peak wavelength, the second peak wavelength, and the third peak wavelength are all included in a visible light range.

10. the plurality of laser diodes includes a fourth laser diode oscillating at a fourth peak wavelength different from any of the first peak wavelength, the second peak wavelength, and the third peak wavelength; The light emitting device according to claim 7 , wherein the plurality of optical waveguides include a fourth optical waveguide that receives the fourth light emitted from the fourth laser diode from a fourth light input end and outputs the fourth light from a fourth light output end.

11. The light emitting device according to claim 10 , wherein the first peak wavelength, the second peak wavelength, the third peak wavelength, and the fourth peak wavelength are all included in a visible light range.

12. The light emitting device of claim 10 , wherein the fourth peak wavelength is in the range of 780 nm to 2000 nm.

13. the first peak wavelength is in the range of 400 nm to 495 nm; the second peak wavelength is in the range of 495 nm to 600 nm; The light emitting device according to claim 7 , wherein the third peak wavelength is in the range of 600 nm to 750 nm.

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