Laser light synthesis device

Abstract

A laser light synthesis device (100) according to the present disclosure comprises: a first input-side optical waveguide (10), a second input-side optical waveguide (11), and a third input-side optical waveguide (12) each having one end located on an input side; an output-side optical waveguide (13) where the respective other ends of the input-side optical waveguides are joined together as one; a red laser light source (20), a green laser light source (21), and a blue laser light source (22) respectively disposed on the one end side of the input-side optical waveguides (10, 11, 12); and a first surface-emitting laser (31) provided on an upper surface side of the first input-side optical waveguide (10) and including a photonic crystal for emitting red laser light into the first input-side optical waveguide (10).

Description

Laser photosynthesizer

[0001] The present disclosure relates to laser light combiners.

[0002] In recent years, the metaverse market, which uses technologies such as virtual reality (VR) and augmented reality (AR) to create virtual spaces that are different from the real world, has grown rapidly, and significant market expansion is expected, especially in the gaming field. Advances in VR / AR technology have made it possible to create immersive virtual spaces, allowing users to act as their own avatars in the virtual space and enjoy interacting with other users and playing games.

[0003] VR / AR device technologies include several components, such as displaying a virtual space using a head-mounted display (HMD) technology, highly accurate tracking technology that reflects user detection and other data on an avatar in the virtual space using motion tracking technology, and low-latency data processing technology. In addition to 3D scanning and environmental mapping as spatial recognition technologies, lasers are used as light sources to three-dimensionally project spatial information into the real world.

[0004] International Publication No. 2020-095417 Japanese Patent Application Laid-Open No. 2009-252958 Japanese Patent Application Laid-Open No. 2019-168673

[0005] Makoto Yukawa, et. al., "638 nm Single Lateral Mode Laser Diode for Micro-Projector Application," ISLC2008 TuC6, pp. 73-74, 2008; Kanji Furuta, Ryuichiro Uemura, "Dry Etching Technology for Automotive 3D Sensors," ULVAC Technical Journal, No. 83, pp. 6-10, September 2019; Yang Gao, et. al. , "Study on angle detection capability of silicon waveguide grating coupler," SPIE 10848, Micro-Optics and MOEMS, 1084807 (12 December 2018) Kazuo Kuroda, "Laser speckle noise," Laser Research, June 2011, pp. 390-394 Wataru Kunishi, et al., "Wide temperature range (-40 to 100°C) operation of photonic crystal lasers," Proceedings of the 68th Spring Meeting of the Japan Society of Applied Physics, vol. 18a-Z10-6 Susumu Noda, et al. , “High-power and high-beam-quality photonic-crystal surface-emitting lasers: a tutorial”, Advances in Optics and Photonics Vol. 15, Issue 4, pp. 977-1032 (2023) Junichi Sakai, “Numerical electromagnetic field analysis method for optical waveguides”, Morikita Publishing, 2015, pp. 178.

[0006] One type of image display used for the above-mentioned applications is a method that takes advantage of the property that white light is produced by combining lasers of the three primary colors of light, red, green, and blue (RGB lasers), and projects an image onto a screen by scanning this combined light beam with a high-speed mirror such as a MEMS (Micro Electro Mechanical System).

[0007] In recent years, silicon photonics, an optical integrated circuit technology that applies the CMOS (Complementary Metal-Oxide-Semiconductor) process of silicon (Si) semiconductors, has made it possible to design optical systems that are smaller and less expensive than conventional spatial optical systems, and the application of silicon photonics to HMDs and small eyeglass-type devices is progressing.

[0008] Furthermore, as described in Patent Document 1, it is expected that new silicon photonics devices that reduce the losses that theoretically occur when laser light of different wavelengths is combined in the combining section of an optical waveguide will be installed in new compact VR / AR equipment.

[0009] However, it is known that the red laser among RGB lasers has a large temperature dependency, with a particularly significant decrease in light output at high temperatures, as described in Non-Patent Document 1. As devices become smaller, VR / AR devices have less room for heat dissipation, and the devices become hot during operations such as graphic processing, which often results in a decrease in the output of the red laser, of the three colors, causing colors to appear darker and, in some cases, causing the light source to malfunction.

[0010] Silicon photonics has the advantage that the refractive index of Si, the core material of the optical waveguide, is higher than that of the compound semiconductor that makes up the light source, so light can be tightly confined within the core layer. However, because Si has high optical absorption, the absorption loss per length of the optical waveguide occurs synergistically with the reduction in optical output of the red laser due to high-temperature operation, causing further problems in the operation of the device.

[0011] As a solution to the above-mentioned problem, for example, Patent Document 2 discloses a laser that uses a gain medium on the InP layer side by providing a resonant structure on one side of a surface-emitting laser made of InP material and laminating a laminated dielectric film on the other side, and mounting the resonant structure on a Si substrate.

[0012] While such surface-emitting lasers typically facilitate alignment with optical circuits in silicon photonics, they have the problem of making it difficult to obtain the required optical output due to structural constraints. According to Non-Patent Document 2, a surface-emitting laser (Vertical Cavity Surface Emitting Laser: VCSEL) has an optical output several tens of times smaller than an edge-emitting laser (Edge Emitting Laser: EEL). Therefore, when using a VCSEL to increase the optical output, it is necessary to array a large number of VCSELs. However, because chips incorporating optical integrated circuits using silicon photonics are miniaturized, there is a problem that it is not possible to secure an area for mounting a sufficient number of arrayed VCSELs to ensure the required optical output.

[0013] Furthermore, Patent Document 3 discloses a technique for implementing an EEL on a silicon photonics optical circuit and transferring light from a laser light source to a silicon photonics optical circuit by an optical coupling method using a grating coupler that utilizes a diffraction grating. However, when single-mode light as described in Non-Patent Document 3 is optically coupled using a silicon photonics grating coupler, the coupling efficiency is about 40%, and the tolerance is narrow at the level of several μm, making alignment difficult and resulting in a problem of reduced coupling efficiency.

[0014] In particular, when the light source is multimode, alignment precision becomes even more stringent. For these reasons, the optical output becomes very small, and this, combined with the fact that the temperature characteristics of the optical output of red lasers deteriorate at high temperatures, poses a practical problem.

[0015] The above has described in detail the decrease in optical output of red lasers when they are operated at high temperatures. In addition to the above problems, when RGB lasers are combined and projected onto a screen, a problem unique to lasers called speckle noise can occur, causing the screen to appear visually glare (Non-Patent Document 4).

[0016] One solution to the speckle noise problem is wavelength multiplexing, which adds laser light sources with slightly shifted oscillation wavelengths. However, due to size constraints, it can be difficult to add new light sources with different oscillation wavelengths to the light source modules of VR / AR devices, especially eyeglass-type devices, even as silicon photonics miniaturizes optical integrated circuits.

[0017] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a laser light combining device that combines and uses multiple light sources in the visible light range, and that has stable light output characteristics even when operated at high temperatures.

[0018] a second input side optical waveguide formed on the substrate and one end located on the input side; a third input side optical waveguide formed on the substrate and one end located on the input side; an output side optical waveguide formed on the substrate and in which the other end of the first input side optical waveguide, the other end of the second input side optical waveguide, and the other end of the third input side optical waveguide are joined together; a red laser light source disposed on one end side of the first input side optical waveguide and emitting red laser light into the first input side optical waveguide; a green laser light source disposed on one end side of the second input side optical waveguide and emitting green laser light into the second input side optical waveguide; and a blue laser light source disposed on one end side of the third input side optical waveguide and emitting blue laser light into the third input side optical waveguide. a first surface-emitting laser provided on an upper surface side of the first input-side optical waveguide and including a photonic crystal that emits red laser light into the first input-side optical waveguide.

[0019] The laser light combining device of the present disclosure has the effect of providing a laser light combining device with stable light output characteristics even when operated at high temperatures.

[0020] FIG. 1 is a schematic view of a laser beam combiner according to embodiment 1. FIG. 2 is a cross-sectional view along the light waveguiding direction of the laser beam combiner according to embodiment 1. FIG. 3 is a schematic view of a laser beam combiner as a comparative example. FIG. 4 is a schematic view of a laser beam combiner according to embodiment 2. FIG. 5 is a schematic view of a laser beam combiner according to embodiment 3. FIG. 6 is a cross-sectional view along the light waveguiding direction of the laser beam combiner according to embodiment 3. FIG. 7 is a schematic view of a laser beam combiner according to embodiment 4. FIG. 8 is a schematic view of a laser beam combiner according to embodiment 5.

[0021] Embodiment 1 Fig. 1 is a schematic view of a laser beam combining device 100 according to embodiment 1. Fig. 2 is a cross-sectional view taken along the light guiding direction in the first input-side optical waveguide of the laser beam combining device 100 according to embodiment 1.

[0022] <Configuration of Laser Light Combiner According to First Embodiment> The laser light combiner 100 according to the first embodiment includes a Si substrate 1, a first input-side optical waveguide 10 having one end located on the input side, a second input-side optical waveguide 11 having one end located on the input side, a third input-side optical waveguide 12 having one end located on the input side, an output-side optical waveguide 13 in which the other end of the first input-side optical waveguide 10, the other end of the second input-side optical waveguide 11, and the other end of the third input-side optical waveguide 12 are coupled together, and an output-side optical waveguide 13 arranged on one end side of the first input-side optical waveguide 10 and arranged in the first input-side optical waveguide 10. a green laser light source 21 arranged on one end side of the second input side optical waveguide 11 and emitting green laser light into the second input side optical waveguide 11; a blue laser light source 22 arranged on one end side of the third input side optical waveguide 12 and emitting blue laser light into the third input side optical waveguide 12; and a first surface-emitting laser 31 provided on the upper surface side of the first input side optical waveguide 10 and equipped with a photonic crystal that emits red laser light into the first input side optical waveguide 10.

[0023] The first input side optical waveguide 10, the second input side optical waveguide 11, the third input side optical waveguide 12, and the output side optical waveguide 13 are each composed of, from the Si substrate 1 side, a lower cladding layer 2 made of SiO2, an optical waveguide layer 3 made of Si, and an upper cladding layer 4 made of SiO2.

[0024] 2 is a cross-sectional view taken along the light guiding direction in the first input-side optical waveguide 10 of the laser beam combining device 100 according to the first embodiment. A first surface-emitting laser 31 equipped with a photonic crystal is disposed on the upper surface side of the first input-side optical waveguide 10, i.e., on the upper clad layer 4. The first surface-emitting laser 31 emits red laser light into the first input-side optical waveguide 10 via a first optical waveguide 14 formed inside the upper clad layer 4 of the first input-side optical waveguide 10.

[0025] The laser light combining device 100 using silicon photonics according to the first embodiment can be realized by applying a CMOS process for Si semiconductors. The substrate that forms the base of the laser light combining device 100 is an SOI (Silicon On Insulator) substrate. The SOI substrate is composed of a Si substrate 1 and a SiO2 layer formed on the Si substrate 1. The SiO2 layer, which is about 3 μm thick and located below the Si optical waveguide layer 3, is used as the lower cladding layer 2, enabling efficient light confinement in the Si optical waveguide layer 3.

[0026] <Method of Manufacturing a Laser Light Combiner According to the First Embodiment> First, in order to remove impurities and surface unevenness from the SOI substrate surface, the SOI substrate is cleaned by methods such as reactive ion etching and mechanical polishing. By smoothing and uniforming the surface of the SOI substrate, light scattering loss due to the influence of surface roughness is reduced.

[0027] After cleaning the SOI substrate, the optical waveguide layer 3 is formed using photolithography. Photoresist is applied to the surface of the SOI substrate, and then a pattern corresponding to the optical waveguide layer 3 is exposed using a photomask. At this time, the pattern is drawn so that each input-side optical waveguide has an appropriate waveguide width and layer thickness. The waveguide width and layer thickness of the optical waveguide layer 3 to be designed will vary depending on whether the laser light source used is single-mode or multi-mode.

[0028] In the first embodiment, a layer thickness of micrometers to submicrometers and a waveguide width of several tens of micrometers to several hundreds of micrometers are patterned by photolithography. Then, the Si layer is vertically processed by dry etching using a reactive ion etching apparatus or the like to form the optical waveguide layer 3 made of Si.

[0029] When light is incident from the incident end face direction, the optical waveguide width of the laser light source and the optical waveguide width of the silicon photonics are different. Therefore, when forming the optical waveguide layer 3, by providing a part at the tip of the optical waveguide layer that converts the spot size of the propagating light, the gap between the two can be eliminated, thereby improving the coupling efficiency.

[0030] Next, the optical waveguide layer 3 made of Si is buried with a thick SiO2 layer using a CVD (Chemical Vapor Deposition) device, etc. The buried SiO2 layer functions as the upper cladding layer 4 in the optical waveguide.

[0031] Finally, the laser light combining device 100 is cut into a desired size using a dicing device, completing the laser light combining device portion using silicon photonics.

[0032] Laser diodes corresponding to each wavelength are used as the laser light sources that make up the fabricated silicon photonics laser light combining device 100. The laser diodes that emit light from the incident end face have oscillation wavelengths corresponding to red, blue, and green, respectively. Note that the laser diode is an example of a laser light source.

[0033] A red laser light source 20 is arranged at one end located on the input side of the first input side optical waveguide 10, a green laser light source 21 is arranged at one end located on the input side of the second input side optical waveguide 11, and a blue laser light source 22 is arranged at one end located on the input side of the third input side optical waveguide 12. The end located on the input side of each input side optical waveguide is also referred to as the incident end face.

[0034] When optically coupling each input-side optical waveguide with each laser light source, it is necessary to precisely control the position and direction of each laser light source. Therefore, it is preferable to provide a power meter at the output of the laser light combining device 100 and fine-tune the mounting position of the optical waveguide while checking the actual optical output. This adjustment allows the light from each laser light source to be coupled to the input-side optical waveguide to the maximum extent possible.

[0035] <First Surface-Emitting Laser> The laser light combining device 100 according to the first embodiment is characterized in that it uses a first surface-emitting laser 31 equipped with a photonic crystal as a light source that emits light from the surface side. Unlike a VCSEL, the first surface-emitting laser 31 confines light two-dimensionally, making the manufacturing method somewhat complicated. However, it is possible to manufacture a laser equipped with a photonic crystal, i.e., a photonic crystal laser, based on design information disclosed in, for example, Non-Patent Document 6. The manufacturing method and element structure of the first surface-emitting laser 31, which is part of the configuration of the laser light combining device 100 according to the first embodiment, will be described below.

[0036] <First Method for Manufacturing Surface-Emitting Laser> An n-type cladding layer, an n-type guide layer, an i-type active layer, a p-type cladding layer, and a p-type contact layer are grown on a GaAs substrate in this order using metal organic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE), or the like.

[0037] The n-type cladding layer and the p-type cladding layer are made of materials such as AlGaAs, AlGaInP, etc. For the n-type guide layer, it is preferable to use a material such as AlGaAs, which has a refractive index as large as possible and allows easy crystal growth on a GaAs substrate.

[0038] The active layer is a periodic GaInP / AlGaInP structure with a thickness of several nanometers, and the light-emitting region corresponding to the oscillation wavelength is grown by crystal growth. On the active layer, a p-type AlGaInP cladding layer and a p-type GaAs contact layer are grown in this order, each having a thickness sufficient to confine light.

[0039] In order to operate the first surface-emitting laser 31 as a photonic crystal laser, it is necessary that materials with different refractive indices are arranged two-dimensionally alternately within the above-mentioned n-type guide layer. To achieve this, after crystal growth up to the n-type guide layer, photolithography technology is used to form a fine pattern in the n-type guide layer so that the period is about ¼ of the desired oscillation wavelength, and then new crystal growth is carried out so that the processed portion is filled with a material with a different refractive index difference.

[0040] After the above-mentioned element structure is formed by crystal growth, the device portion is processed and film-formed by wafer processes such as reactive ion etching, CVD, and vapor deposition, and electrodes are formed to produce an element structure that can operate as a red laser.

[0041] A SiO2 film is formed on the wafer surface by CVD or other methods, and the wafer is processed using a circular pattern mask with a diameter of several hundred microns. Contacts and mounting electrodes are formed in the areas covered by the mask, while an insulating film is formed in the circular areas not covered by the mask to function as an anti-reflection film that also serves as a surface protection film, ensuring sufficiently high transmittance for the laser light extracted from the active layer.

[0042] When mounting a first surface-emitting laser 31 equipped with a photonic crystal on a silicon photonics laser light combining device 100, it is possible to use an ordinary die bonding device to mount the first surface-emitting laser 31 equipped with a photonic crystal on the front side by utilizing an electrode formed on the front side of the laser light combining device 100 and creating a recognition pattern on the back side. During mounting, it is desirable to form an electrode pattern on the front side of the laser light combining device 100 for injecting carriers into the first surface-emitting laser 31.

[0043] <Operation of First Surface-Emitting Laser> The operation of first surface-emitting laser 31 equipped with a photonic crystal produced through the above manufacturing process will be described below. In the following description, first surface-emitting laser 31 will also be simply referred to as a photonic crystal laser.

[0044] The basic structure of a photonic crystal laser is to form a photonic band structure by using two different refractive indexes n a , n b In this case, when l is an integer and a is a real number, and a<A, if the range of position x is expressed by the following formula (1), the refractive index distribution n(x) is expressed by the following formula (2):

[0045]

[0046] On the other hand, when the range of the position x is expressed by the following formula (3), the refractive index distribution n(x) is expressed by the following formula (4).

[0047]

[0048] The optical modes allowed by the periodic structure described above can be obtained by solving Maxwell's equations. The photonic band can be calculated by solving the eigenvalue equations, which are Maxwell's equations for each designed laser light source, using the plane wave expansion method. Let the speed of light be c and the central angular frequency of the photonic band be ω. c , the photonic band gap width is Δω, f a = a / A is the refractive index n a The ratio of the layer to one period is ω c , Δω are expressed by the following equations (5) and (6), respectively (Non-Patent Document 7).

[0049]

[0050] From equations (5) and (6), the photonic band gap width Δω is calculated by the refractive index difference n a and b The photonic band gap width Δω is an index that indicates the intensity of light that can be confined within the resonator of a photonic crystal laser.

[0051] The greater the difference between the two refractive indices, the greater the optical output that can be extracted. The n-type guide layer is made of a crystalline material that is lattice-matched to the substrate, and its refractive index is in the range of 3 to 4, so it can be fabricated by embedding a different material into the shape after micro-fabrication. Furthermore, if the device is fabricated in a processed shape that leaves air (n = 1), the element characteristics will be the best.

[0052] When the above-mentioned device structure is in a forward bias state, that is, when a voltage is applied so that the n-electrode side is negative (-) and the p-electrode side is positive (+), carriers consisting of electrons and holes injected from the front and back sides respectively combine and are amplified in the active layer region, and due to the effect of the photonic band formed by the microfabrication of the n-type guide layer, laser light with high output and excellent beam quality can be extracted from the front side. The oscillation wavelength at this time, λ L is the refractive index of the active layer material, n eff , where m is the order of Bragg reflection, it is expressed by the following equation (7).

[0053]

[0054] For example, the oscillation wavelength λ of the red laser light source 20 L is 635 nm, and the oscillation wavelength λ of the blue laser light source 22 L is 450 nm, and the oscillation wavelength λ of the green laser light source 21 L and 510 nm, respectively, the effective refractive index n eff and the period A of the refractive index distribution, a photonic crystal laser with a desired oscillation wavelength can be obtained.

[0055] <Function of the laser light combining device according to the first embodiment> When the RGB lasers consisting of three color laser lights of red, green, and blue are operated, each laser light is guided through the optical waveguide layer 3 made of Si formed by silicon photonics, and the three color laser lights are combined in the output side optical waveguide 13 to generate white light.

[0056] By separately placing a mirror such as an optical system or MEMS at the external output destination of the laser light combining device 100, it is possible to scan the output beam and draw a desired image on a screen.

[0057] When each laser light source is operated in single mode, the mutual interference of coherent light causes the laser light to scatter on the object, generating a speckle pattern, a random interference pattern. This is called the speckle phenomenon, and appears as a bright and dark speckled pattern, causing image noise that degrades image quality and appears glaring, which is unpleasant. There are several methods for reducing this speckle noise, but the wavelength multiplexing method, which overlaps light of different wavelengths, is often used.

[0058] However, in the laser light combining device 100 formed using silicon photonics, the chip itself is miniaturized, with the size of the elements being on the order of a few centimeters, so it is difficult to add an additional optical system in the direction of emission from the end face to overlap the light, as it is difficult to secure space to place the additional components.

[0059] On the other hand, in the present disclosure, red lasers with oscillation wavelengths differing by several nm are mounted on the incident direction of the end face, and a first surface-emitting laser 31 using a photonic crystal laser is mounted on the front surface side, and the two oscillation wavelengths are shifted by several nm, thereby enabling noise reduction by wavelength multiplexing against speckle noise. An example of this wavelength shift of several nm is a wavelength shift in the range of 1 nm to 10 nm.

[0060] Furthermore, the light output of the edge-emitting red laser light source 20 is highly temperature dependent, and the light output decreases particularly at high temperatures, but this decrease in light output can be compensated for by the photonic crystal laser, which is a surface-emitting laser.

[0061] In the first embodiment, the optical waveguide layer 3 of the silicon photonics laser beam combining device 100 is described as an example of an optical waveguide layer made of Si. However, the material making up the optical waveguide layer 3 may be any material containing Si, such as SiO or SiN.

[0062] The materials for the guide layer of a photonic crystal laser can be a combination of materials with different refractive index differences, and similar effects can be obtained by using GaAs, AlGaAs, GaInP, AlGaInP, AlInP, etc., which are lattice-matched to GaAs, as the guide layer material.

[0063] <Effects of First Embodiment> As described above, according to the laser beam combining device of the first embodiment, the laser beams from the laser light sources coupled to the input optical waveguides at their incident end faces are combined into one by the output optical waveguide, and the first surface-emitting laser equipped with a photonic crystal is provided on the upper surface of the first input optical waveguide that guides the red laser beam. This makes it possible to compensate for a decrease in the optical output of the red laser beam by the first surface-emitting laser, thereby achieving the effect of obtaining a laser beam combining device with stable optical output characteristics even when operated at high temperatures. As shown in Non-Patent Document 5, surface-emitting lasers equipped with photonic crystals have excellent temperature characteristics of optical output.

[0064] Furthermore, according to another aspect of the laser light combining device of embodiment 1, there is a wavelength difference of several nm between the wavelength of the red laser light emitted by the red laser light source and the wavelength of the red laser light emitted by the first surface-emitting laser, which has the effect of providing a laser light combining device with reduced speckle noise.

[0065] Comparative Example of First Embodiment Fig. 3 is a schematic diagram showing a comparative example of a laser beam combining device. The laser beam combining device 200 according to the comparative example has an element structure in which the first surface-emitting laser 31 is not provided in the laser beam combining device 100 according to the first embodiment.

[0066] In the laser light combining device 200 according to the comparative example, the red laser light source 20 is highly temperature-dependent, and the optical output is significantly reduced at high temperatures. As a result, the output of the red laser light source 20, out of the three colors, is reduced, making the color appear darker, and in some cases, the light source may even break down.

[0067] Furthermore, when the laser light sources are combined and projected onto a screen, speckle noise occurs, which can cause the screen to appear visually glaring.

[0068] Second Embodiment Fig. 4 is a schematic diagram of a laser beam combining device 110 according to a second embodiment.

[0069] <Configuration of Laser Light Combiner According to Second Embodiment> A laser light combiner 110 according to the second embodiment includes a Si substrate 1, a first input-side optical waveguide 10 having one end located on the input side, a second input-side optical waveguide 11 having one end located on the input side, a third input-side optical waveguide 12 having one end located on the input side, an output-side optical waveguide 13 in which the other end of the first input-side optical waveguide 10, the other end of the second input-side optical waveguide 11, and the other end of the third input-side optical waveguide 12 are coupled together, and a green laser light source 21 arranged at one end of the second input side optical waveguide 11 and emitting green laser light into the second input side optical waveguide 11; a blue laser light source 22 arranged at one end of the third input side optical waveguide 12 and emitting blue laser light into the third input side optical waveguide 12; and a first surface-emitting laser 31 provided on the upper surface of the first input side optical waveguide 10 and equipped with a photonic crystal that emits red laser light into the first input side optical waveguide 10.

[0070] The laser light combining device 110 of embodiment 2 differs from the laser light combining device 100 of embodiment 1 in that a red laser light source is not arranged at one end of the input side of the first input side optical waveguide 10.

[0071] In the laser beam combining device 110 according to the second embodiment, it is not necessary to use one end on the input side of the first input-side optical waveguide 10 as an incident end face for laser beams incident from outside. Therefore, in the laser beam combining device 110 according to the second embodiment, only the first surface-emitting laser 31 equipped with a photonic crystal generates red laser beams.

[0072] In the laser beam combining device 110 according to the second embodiment, similarly to the first embodiment, each laser beam can be independently controlled to operate as the laser beam combining device 110 .

[0073] <Operation of the Laser Beam Combiner According to the Second Embodiment> In single-mode, end-emitting lasers, the tolerance for optical axis alignment is extremely narrow, at a few micrometers or less, so alignment must be performed while the light source is being driven. Therefore, alignment takes several minutes per laser light source. In the laser beam combiner 110 according to the second embodiment, the number of laser light sources coupled to the incident end face can be reduced, thereby reducing the overall optical axis alignment time of the laser beam combiner 110, thereby improving work efficiency and enabling an increase in the production volume of laser beam combiners.

[0074] <Effects of Embodiment 2> As described above, according to the laser light combining device of embodiment 2, the number of laser light sources on the incident end face side can be reduced, thereby making it possible to shorten the work time required for optical axis alignment, and since a photonic crystal laser is used as the light source of the laser light, it is possible to obtain a laser light combining device with stable light output characteristics even when operated at high temperatures.

[0075] Embodiment 3 Fig. 5 is a schematic view of a laser beam combining device 120 according to embodiment 3. Fig. 6 is a cross-sectional view along the light guiding direction of the first input-side optical waveguide in the laser beam combining device according to embodiment 3.

[0076] <Configuration of laser light combining device according to embodiment 3> In addition to the configuration of the laser light combining device 110 according to embodiment 2, the laser light combining device 120 according to embodiment 3 further includes a second surface-emitting laser 32 equipped with a photonic crystal that emits red laser light, which is provided adjacent to the first surface-emitting laser 31 on the upper cladding layer 4 of the first input-side optical waveguide 10, and emits the red laser light into the first input-side optical waveguide 10 via a second optical waveguide 15 formed inside the upper cladding layer 4 of the first input-side optical waveguide 10.

[0077] That is, in the laser light combining device 120 according to the third embodiment, a first surface-emitting laser 31 equipped with a photonic crystal that emits red laser light and a second surface-emitting laser 32 equipped with a photonic crystal that also emits red laser light are provided adjacent to each other on the upper surface side of the first input side optical waveguide 10, and the first surface-emitting laser 31 emits red laser light to the first input side optical waveguide 10 via a first optical waveguide 14 formed inside the upper clad layer 4 of the first input side optical waveguide 10, and the second surface-emitting laser 32 emits red laser light to the first input side optical waveguide 10 via a second optical waveguide 15 formed inside the upper clad layer 4 of the first input side optical waveguide 10.

[0078] By using both the first surface-emitting laser 31 and the second surface-emitting laser 32, each equipped with two photonic crystals, as a source of red laser light, it is possible to stabilize the optical output characteristics of the red laser light even during high-temperature operation.

[0079] In the laser beam combining device 120 according to the third embodiment, the wavelength of the red laser light from the first surface-emitting laser 31 and the wavelength of the red laser light from the second surface-emitting laser 32 are set to be shifted by several nanometers. This makes it possible to reduce speckle noise by wavelength multiplexing. An example of this wavelength shift of several nanometers is a wavelength shift in the range of 1 nm to 10 nm.

[0080] <Effects of Third Embodiment> As described above, according to the laser light combining device of the third embodiment, the first surface-emitting laser and the second surface-emitting laser are provided adjacent to each other on the upper surface side of the first input-side optical waveguide, and red laser light is supplied by the two lasers, the first surface-emitting laser and the second surface-emitting laser. This makes it possible to reduce the number of laser light sources on the incident end face side, thereby shortening the work time required for optical axis alignment, and it is possible to obtain the effect of obtaining a laser light combining device with stable optical output characteristics even when operated at high temperatures.

[0081] Furthermore, according to another aspect of the laser light combining device of embodiment 3, there is a wavelength difference of several nanometers between the wavelength of the red laser light emitted by the first surface-emitting laser and the wavelength of the red laser light emitted by the second surface-emitting laser, which has the effect of providing a laser light combining device with reduced speckle noise.

[0082] Fourth Embodiment Fig. 7 is a schematic view of a laser beam combining device 130 according to a fourth embodiment.

[0083] <Configuration of Laser Light Combiner According to Fourth Embodiment> A laser light combiner 130 according to the fourth embodiment includes a Si substrate 1, a first input side optical waveguide 10 having one end located on the input side, a second input side optical waveguide 11 having one end located on the input side, a third input side optical waveguide 12 having one end located on the input side, each formed on the Si substrate 1, an output side optical waveguide 13 in which the other end of the first input side optical waveguide 10, the other end of the second input side optical waveguide 11, and the other end of the third input side optical waveguide 12 are coupled together, a red laser light source 20 arranged on one end side of the first input side optical waveguide 10 and emitting red laser light into the first input side optical waveguide 10, and a green laser light source 21 arranged on one end side of the second input side optical waveguide 11 and emitting green laser light into the second input side optical waveguide 11. a blue laser light source 22 disposed on one end of the third input side optical waveguide 12 and emitting blue laser light into the third input side optical waveguide 12; a first surface-emitting laser 31 disposed on the upper surface of the first input side optical waveguide 10 and equipped with a photonic crystal for emitting red laser light into the first input side optical waveguide 10; a third surface-emitting laser 33 disposed on the upper surface of the second input side optical waveguide 11 and equipped with a photonic crystal for emitting green laser light into the second input side optical waveguide 11; and a fourth surface-emitting laser 34 disposed on the upper surface of the third input side optical waveguide 12 and equipped with a photonic crystal for emitting blue laser light into the third input side optical waveguide 12.

[0084] That is, the laser light combining device 130 of embodiment 4 includes, in addition to the configuration of the laser light combining device 100 of embodiment 1, a third surface-emitting laser 33 provided on the upper surface side of the second input side optical waveguide 11, and a fourth surface-emitting laser 34 provided on the upper surface side of the third input side optical waveguide 12.

[0085] The first surface-emitting laser 31 emits red laser light into the first input-side optical waveguide 10 via a first optical waveguide 14 formed inside the upper cladding layer 4 of the first input-side optical waveguide 10. The third surface-emitting laser 33 emits green laser light into the second input-side optical waveguide 11 via a third optical waveguide 16 formed inside the upper cladding layer 4 of the second input-side optical waveguide 11. The fourth surface-emitting laser 34 emits blue laser light into the third input-side optical waveguide 12 via a fourth optical waveguide 17 formed inside the upper cladding layer 4 of the third input-side optical waveguide 12.

[0086] There is a wavelength difference of several nm between the wavelength of the red laser light from the red laser light source 20 and the wavelength of the red laser light from the first surface-emitting laser 31, there is a wavelength difference of several nm between the wavelength of the green laser light from the green laser light source 21 and the wavelength of the green laser light from the third surface-emitting laser 33, and there is a wavelength difference of several nm between the wavelength of the blue laser light from the blue laser light source 22 and the wavelength of the blue laser light from the fourth surface-emitting laser 34.

[0087] <Function of the Laser Light Combining Device According to Embodiment 4> The subset of colors when viewing videos and photographs on a screen is called a color gamut, and is represented by the RGB colors commonly used on computer monitors and the like. In reality, the chromaticity that humans can perceive is defined by the CIE 1931 chromaticity diagram, with green being the color that humans perceive best. In addition to the effect of expanding the color gamut of the three primary colors, RGB, by using light sources with different oscillation wavelengths, as in embodiment 1, by using both edge-emitting and surface-emitting lasers, speckle noise is reduced and the light output characteristics are stable even when operating at high temperatures.

[0088] <Effects of Embodiment 4> As described above, the laser light combining device according to embodiment 4 has the effect of making it possible to widen the color gamut by using laser light of multiple oscillation wavelengths, and further making it possible to reduce speckle noise by superimposing different wavelengths in each laser light, and also making it possible to obtain a laser light combining device with stable light output characteristics even when operated at high temperatures.

[0089] Fifth Embodiment Fig. 8 is a schematic view of a laser beam combining device 140 according to a fifth embodiment.

[0090] <Configuration of Laser Light Combiner According to Fifth Embodiment> A laser light combiner 140 according to the fifth embodiment includes a Si substrate 1, a first input side optical waveguide 10 having one end located on the input side, a second input side optical waveguide 11 having one end located on the input side, a third input side optical waveguide 12 having one end located on the input side, an output side optical waveguide 13 in which the other end of the first input side optical waveguide 10, the other end of the second input side optical waveguide 11, and the other end of the third input side optical waveguide 12 are coupled together, and an output side optical waveguide 13 arranged on one end side of the first input side optical waveguide 10 and emitting red laser light into the first input side optical waveguide 10. a green laser light source 21 arranged on one end side of the second input side optical waveguide 11 and emitting green laser light into the second input side optical waveguide 11; a blue laser light source 22 arranged on one end side of the third input side optical waveguide 12 and emitting blue laser light into the third input side optical waveguide 12; and a fifth surface-emitting laser 35 provided on the upper surface side of the output side optical waveguide 13 and equipped with a photonic crystal that emits any one of red laser light, green laser light, and blue laser light into the output side optical waveguide 13.

[0091] The fifth surface-emitting laser 35 emits one of red laser light, green laser light, and blue laser light into the output-side optical waveguide 13 through the fifth optical waveguide 18 formed inside the upper clad layer 4 of the output-side optical waveguide 13.

[0092] <Operation of laser light combining device according to embodiment 5> The laser light combining device 140 according to embodiment 5 is configured such that each laser light source is arranged on the incident end face side, and a fifth surface-emitting laser 35, which is a photonic crystal laser that serves as a light source of a wavelength different from that of each laser light source, is arranged on the upper surface side of the output side optical waveguide 13, and by independently controlling each laser light source, it is possible to perform operations similar to those of the laser light combining device 100 according to embodiment 1.

[0093] <Function of the Laser Light Combiner According to Embodiment 5> When the laser light combiner is used as a light source for VR / AR applications, in the area where three-color single-mode, edge-emitting RGB lasers are combined, theoretically, due to mode competition between the zeroth and first-order light, half of the light is guided within the optical waveguide, while the other half becomes a radiation mode and propagates outside the optical waveguide. Of this, the radiation light radiated outside the optical waveguide no longer returns to the optical waveguide, so the radiation light radiated outside the optical waveguide is purely lost. Therefore, by mounting the laser light combiner 140 on the upper surface side of the output-side optical waveguide 13, which is closer to the output end face than the area where the RGB lasers are combined, it is possible to reduce the loss of light that occurs during combination.

[0094] <Effects of Embodiment 5> As described above, the laser light combining device according to embodiment 5 has the effect of being able to suppress speckle noise by superimposing different wavelengths, and to provide a laser light combining device that has stable light output characteristics even during high-temperature operation, and is further able to reduce the loss of light that occurs during combining.

[0095] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations.

[0096] Therefore, countless variations not illustrated are conceivable within the scope of the technology of the present disclosure, including, for example, cases in which at least one component is modified, added, or omitted, and cases in which at least one component is extracted and combined with a component of another embodiment.

[0097] REFERENCE SIGNS LIST 1 Si substrate, 2 lower cladding layer, 3 optical waveguide layer, 4 upper cladding layer, 10 first input side optical waveguide, 11 second input side optical waveguide, 12 third input side optical waveguide, 13 output side optical waveguide, 14 first optical waveguide, 15 second optical waveguide, 16 third optical waveguide, 17 fourth optical waveguide, 18 fifth optical waveguide, 20 red laser light source, 21 green laser light source, 22 blue laser light source, 31 first surface-emitting laser, 32 second surface-emitting laser, 33 third surface-emitting laser, 34 fourth surface-emitting laser, 35 fifth surface-emitting laser, 100, 110, 120, 130, 140, 200 laser light combining device

Claims

a first input side optical waveguide formed on the substrate, one end located on the input side; a second input side optical waveguide formed on the substrate, one end located on the input side; a third input side optical waveguide formed on the substrate, one end located on the input side; an output side optical waveguide formed on the substrate, in which the other end of the first input side optical waveguide, the other end of the second input side optical waveguide, and the other end of the third input side optical waveguide are joined together; a red laser light source disposed on one end of the first input side optical waveguide, and emitting red laser light into the first input side optical waveguide; a green laser light source disposed on one end of the second input side optical waveguide, and emitting green laser light into the second input side optical waveguide; and a blue laser light source disposed on one end of the third input side optical waveguide, and emitting blue laser light into the third input side optical waveguide. a first surface-emitting laser provided on an upper surface side of the first input-side optical waveguide and including a photonic crystal that emits red laser light into the first input-side optical waveguide.

2. The laser light combining device described in claim 1, characterized in that the wavelength of the red laser light emitted by the red laser light source and the wavelength of the red laser light emitted by the first surface-emitting laser have a wavelength difference of 1 nm or more and 10 nm or less. a second input side optical waveguide formed on the substrate, one end of which is located on the input side; a third input side optical waveguide formed on the substrate, one end of which is located on the input side; an output side optical waveguide formed on the substrate, in which the other end of the first input side optical waveguide, the other end of the second input side optical waveguide, and the other end of the third input side optical waveguide are joined together; a green laser light source disposed on one end of the second input side optical waveguide, and emitting green laser light into the second input side optical waveguide; a blue laser light source disposed on one end of the third input side optical waveguide, and emitting blue laser light into the third input side optical waveguide; and a first surface-emitting laser provided on the upper surface of the first input side optical waveguide, and comprising a photonic crystal, and emitting red laser light into the first input side optical waveguide.

4. A laser light combining device as described in any one of claims 1 to 3, characterized in that the first input side optical waveguide, the second input side optical waveguide, the third input side optical waveguide, and the output side optical waveguide each consist of, from the substrate side, a lower clad layer, an optical waveguide layer, and an upper clad layer.

5. The laser light combining device described in claim 4, characterized in that the first surface-emitting laser is provided on the upper clad layer of the first input side optical waveguide, and emits the red laser light into the first input side optical waveguide via a first optical waveguide formed inside the upper clad layer of the first input side optical waveguide.

6. A laser light combining device as described in claim 5, characterized in that a second surface-emitting laser equipped with a photonic crystal that emits red laser light is provided adjacent to the first surface-emitting laser on the upper clad layer of the first input side optical waveguide, and the red laser light is emitted into the first input side optical waveguide via a second optical waveguide formed inside the upper clad layer of the first input side optical waveguide.

7. A laser light combining device as described in claim 6, characterized in that the wavelength of the red laser light emitted by the first surface-emitting laser and the wavelength of the red laser light emitted by the second surface-emitting laser have a wavelength difference of 1 nm or more and 10 nm or less.

8. A laser light combining device as described in claim 5, further comprising a third surface-emitting laser provided on the upper surface side of the second input side optical waveguide and having a photonic crystal that emits green laser light into the second input side optical waveguide via a third optical waveguide formed inside the upper clad layer of the second input side optical waveguide.

9. A laser light combining device as described in claim 5 or 8, further comprising a fourth surface-emitting laser provided on the upper surface side of the third input side optical waveguide and having a photonic crystal that emits blue laser light into the third input side optical waveguide via a fourth optical waveguide formed inside the upper clad layer of the third input side optical waveguide.

10. A substrate; a first input side optical waveguide formed on the substrate, one end located on the input side; a second input side optical waveguide formed on the substrate, one end located on the input side; a third input side optical waveguide formed on the substrate, one end located on the input side; an output side optical waveguide formed on the substrate, in which the other end of the first input side optical waveguide, the other end of the second input side optical waveguide, and the other end of the third input side optical waveguide are joined together; a red laser light source disposed at one end of the first input side optical waveguide, for emitting red laser light into the first input side optical waveguide; a green laser light source disposed at one end of the second input side optical waveguide, for emitting green laser light into the second input side optical waveguide; and a blue laser light source disposed at one end of the third input side optical waveguide, for emitting blue laser light into the third input side optical waveguide. a fifth surface-emitting laser provided on the upper surface side of the output-side optical waveguide and including a photonic crystal within the output-side optical waveguide that emits any one of red laser light, green laser light, and blue laser light.

11. A laser light combining device as described in claim 10, characterized in that the first input side optical waveguide, the second input side optical waveguide, the third input side optical waveguide, and the output side optical waveguide each consist of, from the substrate side, a lower clad layer, an optical waveguide layer, and an upper clad layer.

12. The laser light combining device of claim 11, wherein the fifth surface-emitting laser is provided on the upper clad layer of the output-side optical waveguide, and emits any one of the red laser light, the green laser light, and the blue laser light into the output-side optical waveguide through a fifth optical waveguide formed inside the upper clad layer of the output-side optical waveguide.

13. A laser light combining device according to any one of claims 1 to 12, wherein the substrate is a silicon substrate.

14. A laser light combining device according to any one of claims 4 to 9, 11 and 12, characterized in that the lower clad layer, the optical waveguide layer and the upper clad layer are made of a material containing silicon.

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