Optical coupler, optical coupling member, visible light source module, and optical engine

Abstract

To provide an optical coupler that can be connected to or integrated with an optical modulator using a lithium niobate film and can cope with a high output.SOLUTION: An optical coupler 100 includes: three light input ports (21-1i, 21-2i, 21-3i) through which a plurality of laser beams having different wavelengths can be respectively incident; two light output ports (22-1o, 22-2o) through which three laser beams can be coupled and emitted; three light input side optical waveguide (21-1, 21-2, 21-3) that respectively extend from the three light input ports (21-1i, 21-2i, 21-3i); two light output side optical waveguides (22-1, 22-2) that respectively extend from the two light output ports (22-1o, 22-2o); and an optical coupling portion 50 to which the three light input side optical waveguides (21-1, 21-2, 21-3) and the two light output side optical waveguides (22-1, 22-2) are connected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical multiplexer, an optical multiplexing member, a visible light source module, and an optical engine. [Background technology]

[0002] Currently, glasses-type terminals are being considered for xR technologies such as VR (Virtual Reality) and AR (Augmented Reality). In particular, in recent years, retinal scanning displays that allow users to view images by forming an image on the user's retina with two-dimensionally scanned light have been attracting attention. In retinal scanning displays, three colors of visible light, generally emitted from light sources such as LEDs (Light Emitting Diodes) or LDs (Laser Diodes) corresponding to the colors R (red), G (green), and B (blue), are combined on one optical axis. The combined three colors of visible light are transmitted to an image display unit. The image display unit two-dimensionally scans the transmitted light and makes it enter the user's pupil. The user views the image as the incident light forms an image on the user's retina. In this case, the retina is the screen that displays the image.

[0003] For example, Patent Document 1 discloses the configuration of a retinal projection display using a Mach-Zehnder type optical modulator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6728596 [Patent Document 2] Patent No. 6787397 [Patent Document 3] Patent No. 6572377 [Patent Document 4] JP 2012-48071 A [Patent Document 5] JP 2020-27170 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the retinal projection display disclosed in Patent Document 1, multiple optical waveguides are arranged close to each other at the exit section, but they are not multiplexed, so the optical axis for each wavelength is different, making it difficult to control the exiting light.

[0006] Also, a visible light modulator using a lithium niobate film is disclosed in Patent Document 2. Although there is a demand for an RGB optical multiplexer that can be connected to or integrated with a visible light modulator using a lithium niobate film, this has not yet been studied.

[0007] Regarding multiplexing of visible light, directional couplers have generally been considered (for example, see Patent Document 3). These are made of glass-based materials and have excellent stability, but when using a lithium niobate substrate with a large Δn, the coupling length becomes long and miniaturization is not possible.

[0008] Patent Documents 4 and 5 disclose the configuration of an RGB multiplexer using an MMI (multimode interferometer), but in both cases the materials used are glass-based, and there is no disclosure at all about a configuration using a lithium niobate film. An MMI-type optical multiplexer uses multiple waveguide ports on the optical input side to input multiple input signals, and on the optical output side, a single waveguide port is used for the output signal, with all input signals being multiplexed and output as an output signal.

[0009] At present, no optical multiplexer capable of handling high output has been investigated.

[0010] The present invention aims to provide an optical multiplexer that can handle high output and can be connected to or integrated with an optical modulator using a lithium niobate film, and an optical multiplexing member, a visible light source module, and an optical engine that are equipped with the same. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides the following means.

[0012] A first aspect of the present invention is an optical multiplexer that multiplexes a plurality of laser beams having different wavelengths, comprising a plurality of optical input ports into which the plurality of laser beams can respectively be input, two or more optical output ports into which the plurality of laser beams can be multiplexed and output, the plurality of optical input side optical waveguides extending from each of the plurality of optical input ports, the two or more optical output side optical waveguides extending from each of the two or more optical output ports, and an optical multiplexing section in which the plurality of optical input side optical waveguides and the two or more optical output side optical waveguides are connected.

[0013] A second aspect of the present invention is an optical multiplexer according to the first aspect, wherein the plurality of optical input ports include two or more optical input ports for at least one laser beam.

[0014] A third aspect of the present invention is an optical multiplexer according to the second aspect, wherein the plurality of optical input ports include two or more optical input ports for each of all the laser beams.

[0015] A fourth aspect of the present invention is the optical multiplexer according to any one of the first to third aspects, wherein the distance between the most distant optical output ports among the two or more optical output ports is 25 μm or less.

[0016] A fifth aspect of the present invention is an optical multiplexer according to any one of the first to fourth aspects, wherein, of the two or more optical input ports provided for one laser beam, the interval between adjacent optical input ports is 0.5 μm or less.

[0017] A sixth aspect of the present invention is an optical multiplexer according to any one of the first to fifth aspects, wherein the thickness of the slab portion provided on the inner side of the optical input side waveguide is greater than the thickness of the slab portion provided on the outer side of the optical input side waveguide.

[0018] A seventh aspect of the present invention is the optical multiplexer according to any one of the first to sixth aspects, wherein the optical multiplexing section is a multi-mode interference type multiplexing section.

[0019] Aspect 8 of the present invention is an optical multiplexing member comprising a substrate made of a material other than lithium niobate, and an optical multiplexing function layer made of a lithium niobate film formed on a main surface of the substrate, in which any one of the optical multiplexers of aspects 1 to 7 is formed in the optical multiplexing function layer.

[0020] A ninth aspect of the present invention is a visible light source module including the optical multiplexing member of the eighth aspect and a plurality of visible laser light sources that emit visible lasers multiplexed by the optical multiplexing member.

[0021] A tenth aspect of the present invention is an optical multiplexing member with an optical modulation function, which comprises a Mach-Zehnder type optical modulator in the optical multiplexing functional layer of the optical multiplexing member of the eighth aspect.

[0022] An eleventh aspect of the present invention is a visible light source module including the optical multiplexing member with optical modulation function of the tenth aspect, and a plurality of visible laser light sources that emit visible lasers multiplexed by the optical multiplexing member with optical modulation function.

[0023] A twelfth aspect of the present invention is an optical engine including the visible light source module of the ninth aspect, and a light scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image.

[0024] A thirteenth aspect of the present invention is an optical engine including the visible light source module of the eleventh aspect, and a light scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image. Effect of the Invention

[0025] According to the present invention, it is possible to provide an optical multiplexer that can be connected to or integrated with an optical modulator using a lithium niobate film and that can handle high output. [Brief description of the drawings]

[0026] [Figure 1]FIG. 1 is a schematic plan view showing an optical multiplexer according to a first embodiment. [Diagram 2] FIG. 11 is a schematic plan view showing an optical multiplexer according to a second embodiment. [Diagram 3] FIG. 11 is a schematic plan view showing an optical multiplexer according to a third embodiment. [Figure 4] 2 is a schematic cross-sectional view taken along line XX' in FIG. 1 of an optical multiplexing member in which the components shown in FIG. 1 are formed in an optical multiplexing function layer made of lithium niobate. [Diagram 5] 1 is a schematic cross-sectional view taken along the YZ plane when the cross section of an MMI type optical multiplexing unit has a trapezoidal shape. [Figure 6] FIG. 1 is a schematic cross-sectional view taken along the YZ plane when a slab portion is provided on the substrate side of an MMI type optical multiplexing portion. [Figure 7] 1 is a schematic cross-sectional view taken along the YZ plane when the cross section of an MMI type optical multiplexing section is trapezoidal and has a slab section on the substrate side. [Figure 8] 11 is a schematic plan view of a modified example of an optical multiplexing member according to an embodiment of the present invention. FIG. [Figure 9] FIG. 2 is a schematic plan view of the visible light source module according to the first embodiment. [Figure 10] FIG. 11 is a schematic plan view of a visible light source module according to a second embodiment. [Figure 11] FIG. 2 is a conceptual diagram for explaining an optical engine according to the present embodiment. [Figure 12A] FIG. 2 is a conceptual diagram for explaining an optical engine according to the present embodiment. [Figure 12B] FIG. 2 is a conceptual diagram for explaining an optical engine according to the present embodiment. [Figure 13] FIG. 13 is a diagram showing the relationship between the laser beam diameter and the distance Z from the laser emission surface corresponding to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and may be appropriately modified and implemented within the scope of the effects of the present invention.

[0028] [Optical multiplexer (first embodiment)] FIG. 1 is a schematic plan view showing an optical multiplexer according to the first embodiment. The optical multiplexer 100 shown in FIG. 1 is an optical multiplexer that multiplexes three laser beams with different wavelengths, and has three optical input ports (21-1i, 21-2i, 21-3i) into which the three laser beams can respectively enter, two optical output ports (22-1o, 22-2o) into which the three laser beams can be multiplexed and output, and three optical input ports (21-1i, 21-2i, 21-3i). The optical multiplexing section 50 includes three optical input side optical waveguides (21-1, 21-2, 21-3) extending therefrom, two optical output side optical waveguides (22-1, 22-2) extending from each of the two optical output ports (22-1o, 22-2o), and an optical multiplexing section 50 to which the three optical input side optical waveguides (21-1, 21-2, 21-3) and the two optical output side optical waveguides (22-1, 22-2) are connected.

[0029] In FIG. 1, the X direction is perpendicular to the side surface 100A on which the optical input port is located, the Y direction is perpendicular to the X direction, and the Z direction is perpendicular to the plane formed by the X and Y directions.

[0030] The optical multiplexer 100 is configured to include two optical output ports that output laser light, and two optical output-side optical waveguides that are connected to the two optical output ports, respectively. By including multiple optical output-side optical waveguides, the power density of the laser light that is guided through the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides. This is particularly an effective measure against damage to the optical waveguide of a high-power laser (e.g., laser light of 100 mW or more).

[0031] The dimensions of the optical input side optical waveguide and the optical output side optical waveguide can be, for example, 0.1 to 5 μm in width and 0.1 to 5 μm in height.

[0032] The optical multiplexer 100 is configured to be compatible with three laser beams having different wavelengths, but is not limited to three laser beams having different wavelengths, and may be configured for two laser beams having different wavelengths. The number of optical input ports and the number of optical input side optical waveguides connected to the optical input ports may be changed according to the number of laser beams. The input laser beams having different wavelengths can be visible light, but are not limited to visible light. A configuration may be used for visible laser beams and non-visible laser beams.

[0033] The optical multiplexer 100 has four sides 100A, 100B, 100C, and 100D, with three optical input ports provided on the first side 100A and two optical output ports provided on the third side 100C, but the two optical output ports can also be provided on the second side 100B or the fourth side 100D.

[0034] Distance d between the two optical output ports 22-1o and 22-2o o It is preferable that the distance d is 25 μm or less. In the case where the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams are seen as one beam, and a clear image is produced. o is the distance between the center of the optical output port 22-1o and the center of the optical output port 22-2o as shown in FIG.

[0035] The optical multiplexer 50 is a multi-mode interference (MMI) type multiplexer, but a directional coupler or a Y-shaped multiplexer may also be used. The optical multiplexer 50 is a 3-input 2-output MMI type optical multiplexer. In the optical multiplexer 100, the MMI type optical multiplexing section 50 has a one-stage configuration, but may have a two or more stages.

[0036] It is preferable that the optical input side optical waveguide and the optical output side optical waveguide connected to the optical multiplexing unit 50, which is an MMI type optical multiplexer, have a tapered section that is wider as it approaches the input / output port of the optical multiplexing unit 50. The optical input side optical waveguide and the optical output side optical waveguide connected to the optical multiplexing unit 50 are set to propagate single mode (zeroth mode, fundamental mode), and the optical multiplexing unit 50 is set to propagate multimode (zeroth mode to higher mode). Therefore, when the light is input from the optical input side optical waveguide to the optical multiplexing unit 50 and output from the optical multiplexing unit 50 to the optical output side optical waveguide, a coupling loss occurs due to mode mismatch between the input single mode and multimode. On the other hand, if a tapered section is provided at the input / output port, the mode mismatch between the input single mode and multimode is alleviated, and the coupling loss is reduced. The wider the width of the tapered section, the more the mode mismatch is alleviated, and the greater the effect of reducing the coupling loss.

[0037] Although the three optical input side optical waveguides (21-1, 21-2, 21-3) and the two optical output side optical waveguides (22-1, 22-2) shown in Fig. 1 are configured to extend linearly in the x direction, they are not limited to such a configuration. For example, they may have curved portions as in the optical output side optical waveguides (22-11, 22-12, 22-13) shown in Fig. 3.

[0038] [Optical multiplexer (second embodiment)] 2 is a schematic plan view showing an optical multiplexer according to the second embodiment. In the figure, L1, L2, and L3 conceptually show three laser beams. Explanations of members similar to those in the first embodiment may be omitted.

[0039] The optical multiplexer 101 shown in FIG. 2 is an optical multiplexer that multiplexes three laser beams with different wavelengths, and has two optical input ports for each of the three laser beams (L1, L2, L3), for a total of six optical input ports (21-11i, 21-12i, 21-21i, 21-22i, 21-31i, 21-32i), two optical output ports (22-1o, 22-2o) from which the three laser beams can be multiplexed and output, and six optical input ports (21-11i, 21-12i, 21-21i, 21-22i, 21-32i). the six optical input side optical waveguides (21-11, 21-12, 21-21, 21-22, 21-31, 21-32) extending from each of the two optical output ports (22-1o, 22-2o), and an optical multiplexing section 51 to which the six optical input side optical waveguides (21-11, 21-12, 21-21, 21-22, 21-31, 21-32) and the two optical output side optical waveguides (22-1, 22-2) are connected.

[0040] The optical multiplexer 101 has two optical input ports for each laser light, through which the laser light is input. By providing a plurality of optical input ports for each laser light, the power density of the laser light guided through the optical waveguide on the optical input side is dispersed, making it possible to suppress damage to the optical waveguide on the optical input side. In other words, the optical multiplexer of the second embodiment is configured to include not only an optical output side optical waveguide but also multiple optical input side optical waveguides for each laser light, so that the power density of the laser light guided through the optical input side optical waveguides is distributed, and damage to the optical input side optical waveguides can be suppressed.

[0041] Distance d between optical input ports 21-11i and 21-12i i , the distance d between the optical input ports 21-21i and 21-22i i , and the distance d between the optical input ports 21-31i and 21-23i i is preferably 0.5 μm or less. Since the laser light spreads in a Gaussian shape, the power is stronger closer to the center. Therefore, as much power as possible of the laser light L1 is input to the optical waveguide on the optical input side. In addition, if the spacing between the optical input ports is 0.5 μm or less, the decrease in the coupling efficiency between the laser and the optical waveguide on the optical input side can be suppressed.

[0042] As in the first embodiment, the distance d between the two optical output ports 22-1o and 22-2o is o It is preferable that the distance d is 25 μm or less. In the case where the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams are seen as one beam, and a clear image is produced. o is the distance between the center of the optical output port 22-1o and the center of the optical output port 22-2o, as shown in FIG.

[0043] The optical multiplexing unit 51 is a 6-input, 2-output MMI type optical multiplexer.

[0044] [Optical multiplexer (third embodiment)] 3 is a schematic plan view showing an optical multiplexer according to the third embodiment. In the figure, L1, L2, and L3 conceptually show three laser beams. Descriptions of members similar to those in the above embodiments may be omitted.

[0045] The optical multiplexer 102 shown in FIG. 3 is an optical multiplexer that multiplexes three laser beams of different wavelengths, and has three optical input ports for each of the three laser beams (L1, L2, L3), for a total of nine optical input ports (21-111i, 21-112i, 21-113i, 21-121i, 21-122i, 21-123i, 21-131i, 21-132i, 21-133i). The optical multiplexer 102 has three optical output ports (22-11o, 22-12o, 22-13o) from which the three laser beams can be multiplexed and output, and nine optical input ports (21-111i, 21-112i, 21-113i, 21-121i, 21-122i, 21-123i, 21-131i, 21-132i, nine optical input side optical waveguides (21-111, 21-112, 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, 21-133) extending from each of the optical input ports (21-111, 21-112, 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, 21-133) and three optical output side optical waveguides (22-11o, 22-12o, 22-13o) extending from each of the optical output ports (22-11o, 22-12o, 22-13o). and an optical multiplexing section 52 to which nine optical input side optical waveguides (21-111, 21-112, 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, 21-133) and three optical output side optical waveguides (22-11, 22-12, 22-13) are connected.

[0046] The optical multiplexer 102 is configured to include three optical output ports that output laser light, and three optical output-side optical waveguides that are connected to the three optical output ports, respectively. By including multiple optical output-side optical waveguides, the power density of the laser light that is guided through the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides. The optical multiplexer of the third embodiment, like the optical multiplexer of the second embodiment, is configured to include not only an optical output side optical waveguide but also multiple optical input side optical waveguides for each laser light. This distributes the power density of the laser light guided through the optical input side optical waveguides, making it possible to suppress damage to the optical input side optical waveguides.

[0047] As in the first embodiment, of the three optical output ports 22-11o, 22-12o, and 22-13o, the distance d between the two optical output ports 22-11o and 22-12o at both ends is o The distance d between two adjacent optical output ports 22-11o and 22-13o is preferably 25 μm or less. o1 , and the distance d between the two optical output ports 22-12o and 22-13o o1 It is preferable that the thickness is 10 μm or less. This is because when the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams appear as one, resulting in a clear image. o is the distance between the center of the optical output port 22-1o and the center of the optical output port 22-2o, as shown in FIG.

[0048] As with the optical multiplexer 101 shown in FIG. 2, among the optical input ports L1, L2, and L3 for each laser light, the interval between adjacent optical input ports is preferably 0.5 μm or less. That is, the interval between the optical input ports 21-111i and 21-112i, the interval between the optical input ports 21-112i and 21-113i, the interval between the optical input ports 21-121i and 21-122i, the interval between the optical input ports 21-122i and 21-123i, the interval between the optical input ports 21-131i and 21-132i, and the interval between the optical input ports 21-132i and 21-133i are preferably 0.5 μm or less. Since the laser light spreads in a Gaussian shape, the power is stronger closer to the center. This is because the power of the laser light L1 is input to the optical waveguide on the optical input side as much as possible. In addition, when the interval between the optical input ports is 0.5 μm or less, the decrease in the coupling efficiency between the laser and the optical waveguide on the optical input side can be suppressed.

[0049] The optical multiplexing unit 52 is a 6-input, 3-output MMI type optical multiplexer.

[0050] [Optical multiplexing member] The optical multiplexing member according to the embodiment of the present invention includes a substrate made of a material different from lithium niobate, and an optical multiplexing functional layer made of a lithium niobate film formed on the main surface of the substrate, and the optical multiplexer according to the embodiment is formed in the optical multiplexing functional layer. In the components described below, components having the same functions as those in the above embodiment may be given the same reference numerals and their description may be omitted. In the optical multiplexing member 200 shown in FIG. 4, the optical multiplexer 100 shown in FIG. 1 is formed in the optical multiplexing functional layer.

[0051] FIG. 4 is a schematic cross-sectional view of the optical multiplexer 100 shown in FIG. 1 cut along the YZ plane (XX' in FIG. 1) of the optical multiplexing member 200 formed in an optical multiplexing functional layer made of lithium niobate. The optical multiplexing member 200 shown in FIG. 4 includes a substrate 10 made of a material different from lithium niobate, and an optical multiplexing functional layer 20 made of lithium niobate and formed on a main surface of the substrate 10. The optical input port, the optical output port, the optical multiplexing section, the input taper section, the output taper section, the optical input side optical waveguide, and the output side optical waveguide are formed in the optical multiplexing functional layer 20.

[0052] In the optical multiplexing member 200, when the refractive index difference between the waveguide core film and the waveguide clad film is Δn, if the waveguide core film is made of lithium niobate, Δn can be designed to be a larger value than when using materials such as glass, and the radius of curvature of the optical waveguide can be made smaller. Furthermore, by using a multimode interference type optical multiplexing section, an increase in coupling length can be prevented compared to when a directional coupler is used, thereby achieving both improved design freedom and miniaturization.

[0053] The optical multiplexing functional layer 20 comprises a waveguide core film 24 made of a lithium niobate film in which the optical input port, the optical output port, the optical multiplexing section, the optical input side optical waveguide, and the output side optical waveguide are formed, and a waveguide clad (buffer) film 25 formed on the waveguide core film 24 so as to cover these. Hereinafter, the reference symbol 24 may also be used to refer to the lithium niobate film.

[0054] Examples of the substrate 10 include a sapphire substrate, a Si substrate, and a thermally oxidized silicon substrate. Since the optical multiplexing functional layer 20 is made of a lithium niobate (LiNbO3) film, there is no particular limitation as long as the refractive index is lower than that of the lithium niobate film, but a sapphire single crystal substrate or a silicon single crystal substrate is preferred as a substrate on which the single crystal lithium niobate film can be formed as an epitaxial film. The crystal orientation of the single crystal substrate is not particularly limited, but for example, since a c-axis oriented lithium niobate film has three-fold symmetry, it is desirable that the underlying single crystal substrate also has the same symmetry, and in the case of a sapphire single crystal substrate, a c-plane substrate is preferred, and in the case of a silicon single crystal substrate, a (111) plane substrate is preferred.

[0055] The lithium niobate film is, for example, a c-axis oriented lithium niobate film. The lithium niobate film is, for example, an epitaxial film epitaxially grown on the substrate 10. The epitaxial film is a single crystal film whose crystal orientation is aligned by the underlying substrate. The epitaxial film is a film having a single crystal orientation in the z direction and the xy in-plane direction, and the crystals are aligned in the x-axis, y-axis, and z-axis directions. Whether the film formed on the substrate 10 is an epitaxial film can be proved by, for example, checking the peak intensity and pole at the orientation position in 2θ-θ X-ray diffraction.

[0056] Specifically, when measured by 2θ-θX-ray diffraction, all peak intensities other than the target plane are 10% or less, preferably 5% or less, of the maximum peak intensity of the target plane. For example, when the lithium niobate film is a c-axis oriented epitaxial film, the peak intensities other than the (00L) plane are 10% or less, preferably 5% or less, of the maximum peak intensity of the (00L) plane. Here, (00L) is a general designation for equivalent planes such as (001) and (002).

[0057] Moreover, the conditions for confirming the peak intensity at the orientation position described above only indicate the orientation in one direction. Therefore, even if the above conditions are obtained, if the crystal orientation is not uniform in the plane, the intensity of the X-rays will not increase at a specific angle position, and no poles will be observed. For example, in the case of a lithium niobate film, since LiNbO3 has a trigonal crystal structure, there are three poles of LiNbO3 (014) in the single crystal. In the case of lithium niobate, it is known that the epitaxial growth occurs in a so-called twin state in which crystals rotated 180° around the c-axis are symmetrically bonded. In this case, the three poles are symmetrically bonded to two, so there are six poles. In addition, when a lithium niobate film is formed on a silicon single crystal substrate with a (100) plane, the substrate is four-fold symmetric, so 4x3=12 poles are observed. In this disclosure, a lithium niobate film epitaxially grown in a twin state is also included in the epitaxial film.

[0058] The composition of lithium niobate is Li x NbA y O z A is an element other than Li, Nb, and O. x is 0.5 or more and 1.2 or less, and preferably 0.9 or more and 1.05 or less. y is 0 or more and 0.5 or less. z is 1.5 or more and 4.0 or less, and preferably 2.5 or more and 3.5 or less. The element A is, for example, K, Na, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Cr, Mo, W, Fe, Co, Ni, Zn, Sc, or Ce, and two or more of these elements may be combined. Furthermore, the lithium niobate film may be a lithium niobate single crystal thin film bonded onto a substrate.

[0059] The thickness of the lithium niobate film is, for example, 2 μm or less. The thickness of the lithium niobate film refers to the thickness of the portion other than the ridge. The thickness of the lithium niobate film can be optimally designed according to the wavelength and ridge shape to be used.

[0060] The waveguide is a ridge protruding from the first surface 24A of the lithium niobate film 24. The first surface 24A is the upper surface of the portion (slab layer) of the lithium niobate film 24 other than the ridge. As shown in FIG. 4, the cross-sectional shape of the cross-sectional shape-defining portion of the optical input-side optical waveguides 21-1, 21-2, and 21-3 is rectangular, but any shape that can guide light may be used, for example, a trapezoidal shape, a triangular shape, a semi-circular shape, etc. The width Wa in the y direction of the three ridges is preferably 0.2 μm or more and 5.0 μm or less, and the height of the three ridges (the protruding height Ha from the first surface 24A) is preferably, for example, 0.1 μm or more and 1.0 μm or less. The same applies to other optical waveguides.

[0061] The optical input-side optical waveguides 21-1, 21-2, 21-3 and the other optical waveguides shown in FIG. 1 can propagate in single mode by setting their sizes to about the wavelength of the laser light.

[0062] <MMI-Type Optical Combiner> (1) MMI-Type Optical Combiner with a Trapezoidal Cross-Section The above-mentioned optical combiner is an MMI-type optical combiner (hereinafter sometimes referred to as an "MMI-type optical combiner"). As shown in FIG. 5, the cross-section of the MMI-type optical combiner cut in the direction perpendicular to the light propagation direction may preferably be trapezoidal. Also, the inclination angle θ of this trapezoidal shape may preferably be 40° to 85°. This is because the dimensional margin of the width W of the MMI-type optical combiner is improved, the optimal width of the MMI-type optical combiner becomes larger, and processing becomes easier. This result is obtained by comparing the propagation losses of RGB three-color light by simulation between the case where the cross-section of the MMI-type optical combiner cut in the direction perpendicular to the light propagation direction is trapezoidal and the case where it is rectangular. In the model used in this simulation, the height T of the MMI type optical multiplexing section (ridge) was set to 0.7 μm, and the width at 1 / 2 the height T of the MMI type optical multiplexing section was set to W. The center CC of the ridge was fixed and the inclination angle θ between the lower surface and the inclined section was either widened or narrowed on either side by dW / 2 (hence, dW in total) to simulate the propagation loss during RGB multiplexing. In a 2x1 MMI type optical multiplexer that multiplexes two colors of light, when θ is 85°, 70°, and 40°, the margin is 0.3 μm in all cases, and the optimal width W is 6.6 μm, 6.6 μm, and 6.9 μm, respectively.

[0063] (2) MMI-type optical multiplexer with slab section The MMI type optical multiplexer may have a slab section provided on the substrate side as shown in FIG. The MMI type optical multiplexing section 50A shown in FIG. 6 has a ridge 50A-1 and further has a slab section 50A-2 on the substrate side. By having a slab portion, the width dimension margin may be further expanded, making processing even easier. Also, the optimum width W may be further expanded, making processing even easier. When the MMI optical multiplexing section has the configuration of the model shown in Figure 6, a simulation was performed on the propagation loss (dB) of the fundamental mode (TM0) and higher order modes (TM1, TM2) of each of the three RGB colors when RGB is multiplexed. The height Tslab of the slab portion is set to 0.2 μm, and the height T of the MMI optical multiplexing section is the sum of the height of the ridge 50A-1 and the height of the slab portion 50A-2. The width W of the MMI optical multiplexing section is set to 6.5 μm. For comparison, the propagation loss of light in the case where there is a slab section was compared to that in the case where there is no slab section, and the difference in propagation loss in RGB was smaller in the case where there is a slab section than in the case where there is no slab section. In addition, the difference in propagation loss between the case where there is a slab section and the case where there is no slab section showed that the propagation loss of higher-order modes was large, and propagation was suppressed. Therefore, it was found that providing a slab section is effective in achieving single mode.

[0064] 7, an MMI-type optical multiplexer 50B having a trapezoidal cross section may have a ridge 50B-1 and a slab 50B-2 on the substrate side. By having a slab, the width dimension margin is further increased, and the optimum width W is further increased, which may facilitate processing.

[0065] FIG. 8 is a schematic plan view of a modified example of the optical multiplexing member according to the embodiment of the present invention. The optical multiplexing member 300 shown in Figure 8 is an optical multiplexing member with an optical modulation function, which includes a substrate 10 (see Figure 4) made of a material other than lithium niobate, and an optical multiplexing function layer 20 made of a lithium niobate film formed on the main surface of the substrate 10, and has an optical modulation function within the optical multiplexing function layer 20.

[0066] The optical multiplexing member 300 with an optical modulation function includes the optical multiplexing section 50 (see FIG. 1) according to the above embodiment, and a Mach-Zehnder type optical modulator 40. The Mach-Zehnder type optical modulator 40 includes three Mach-Zehnder type optical waveguides 40-1, 40-2, and 40-3.

[0067] A known Mach-Zehnder type optical modulator or an optical waveguide can be used as the Mach-Zehnder type optical modulator 40, which splits (demultiplexes) an optical beam with a uniform wavelength and phase into two paired beams, gives each beam a different phase, and then combines (combines) them. The intensity of the combined optical beam changes depending on the difference in phase.

[0068] Each of the Mach-Zehnder type optical waveguides 40 (40-1, 40-2, 40-3) shown in FIG. 8 includes a first optical waveguide 41, a second optical waveguide 42, an input path 43, an output path 44, a branching portion 45, and a coupling portion 46. The output path 44 of the Mach-Zehnder type optical waveguide 40-1 is connected to the optical input side optical waveguide 21-1 of the optical multiplexing section 50. In addition, the output path 44 of the Mach-Zehnder type optical waveguide 40-2 is connected to the optical input side optical waveguide 21-2 of the optical multiplexing section 50. In addition, the output path 44 of the Mach-Zehnder type optical waveguide 40-3 is connected to the optical input side optical waveguide 21-3 of the optical multiplexing section 50. The first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 8 are configured to extend linearly in the x direction except for the vicinity of the branching portion 45 and the vicinity of the coupling portion 46, but are not limited to such a configuration. The first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 8 have approximately the same length. The branching portion 45 is between the input path 43 and the first optical waveguide 41 and the second optical waveguide 42. The input path 43 is connected to the first optical waveguide 41 and the second optical waveguide 42 via the branching portion 45. The coupling portion 46 is between the first optical waveguide 41 and the second optical waveguide 42 and the output path 44. The first optical waveguide 41 and the second optical waveguide 42 are connected to the output path 44 via the coupling portion 46.

[0069] The electrodes 29 and 26 are electrodes that apply a modulation voltage to each of the Mach-Zehnder optical waveguides 40-1, 40-2, and 40-3 (hereinafter, sometimes simply referred to as "each Mach-Zehnder optical waveguide 40"). The electrode 29 is an example of a first electrode, and the electrode 26 is an example of a second electrode. One end of the electrode 29 is connected to a power source 131, and the other end is connected to a termination resistor 132. One end of the electrode 26 is connected to the power source 131, and the other end is connected to the termination resistor 132. The power source 131 is a part of a drive circuit that applies a modulation voltage to each of the Mach-Zehnder optical waveguides 40. For the sake of simplicity, the electrodes 29 and 26 are drawn only on the part of the Mach-Zehnder optical waveguide 40-3.

[0070] The electrodes 27 and 28 are electrodes that apply a DC bias voltage to each Mach-Zehnder type optical waveguide 40. One end of the electrode 27 and one end of the electrode 28 are connected to a power source 133. The power source 133 is a part of a DC bias application circuit that applies a DC bias voltage to each Mach-Zehnder type optical waveguide 40. When a DC bias voltage is superimposed on the electrodes 29, 26, the electrodes 27, 28 do not need to be provided. Also, ground electrodes may be provided around the electrodes 29, 26, 27, 28.

[0071] The optical multiplexing member 300 has one optical input port 40-1i, 40-2i, 40-3i for each of the three laser beams, and has an optical input side optical waveguide for each optical input port. However, as illustrated in Figures 2 and 3, the optical multiplexing member 300 may have a plurality of optical input ports, such as two optical input ports or three optical input ports, for each of the three laser beams, and may have an optical input side optical waveguide for each optical input port. In this case, each of the optical input side optical waveguides may be a Mach-Zehnder type optical waveguide, or a part of the optical input side optical waveguides may be a Mach-Zehnder type optical waveguide.

[0072] Also, the optical output port may have three or more optical output ports, and each optical input port may have an optical output side optical waveguide.

[0073] [Visible Light Source Module (First Embodiment)] The visible light source module according to the first embodiment includes the optical multiplexing member according to the above embodiments, and a plurality of visible light laser light sources that emit visible light multiplexed in the optical multiplexing member. 9 is a schematic plan view of a visible light source module according to this embodiment, which illustrates an example of a visible light source module including the optical multiplexing member 200 illustrated in FIG.

[0074] 9 includes an optical multiplexing member 200 having an optical multiplexing section 50, and three visible laser light sources 30 (30-1, 30-2, 30-3) that emit visible light multiplexed by the optical multiplexing member 200. The optical multiplexing member 200 includes a substrate 10 (see FIG. 4) made of a material different from lithium niobate, and an optical multiplexing functional layer 20 (see FIG. 4) made of lithium niobate and formed on the main surface of the substrate 10, and has a side surface 200A as a light incident surface. Regarding the components shown in FIG. 9, components having the same functions as those described above are denoted by the same reference numerals, and the description thereof may be omitted.

[0075] Various laser elements can be used as the visible light laser light source 30. For example, commercially available laser diodes (LDs) for red light, green light, blue light, etc. can be used. For red light, light with a peak wavelength of 600 nm or more and 750 nm or less can be used, for green light, light with a peak wavelength of 500 nm or more and 600 nm or less can be used, and for blue light, light with a peak wavelength of 380 nm or more and 500 nm or less can be used. In the visible light source module 1000, for example, the visible light laser light sources 30-1, 30-2, and 30-3 are an LD that emits red light, an LD that emits green light, and an LD that emits blue light, respectively. The LDs 30-1, 30-2, and 30-3 are disposed at intervals from each other in a direction substantially perpendicular to the emission direction of the light emitted from each LD, and are provided on the upper surface of the subcarrier 120.

[0076] In the visible light source module 1000, the number of visible light laser light sources is 3, but the number is not limited to 3 as long as there is more than one, and may be 2, 4 or more. The multiple visible light laser light sources may all emit light with different wavelengths, or there may be visible light laser light sources that emit light with the same wavelength. In addition, light other than red (R), green (G), and blue (B) may be used as the emitted light, and the mounting order of red (R), green (G), and blue (B) explained using the drawings does not have to be in this order and can be changed as appropriate.

[0077] The LD 30 can be mounted as a bare chip on the subcarrier 120. The subcarrier 120 is made of, for example, aluminum nitride (AlN), aluminum oxide (Al2O3), silicon (Si), or the like.

[0078] The subcarrier 120 can be directly bonded to the substrate 10 via a metal bonding layer. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. By configuring the subcarrier 120 and the substrate 10 to be bonded via a metal bonding layer, the relative positions of the subcarrier 120 and the substrate 10 can be adjusted during manufacture to align the optical axis position of the laser light so that the optical axes of each visible light laser coincide with the respective axes of the first optical input side optical waveguide 21-1, the second optical input side optical waveguide 21-2, and the third optical input side optical waveguide 21-3 (active alignment).

[0079] In the visible light source module 1000, the three optical input ports 21-1i, 21-2i, and 21-3i of the optical multiplexing section 50 face the exits of the LDs 30 (30-1, 30-2, and 30-3), and are positioned so that the light emitted from the exit surface of each LD 30 can be incident on the optical input ports 21-1i, 21-2i, and 21-3i. Also, the axes of the optical input side optical waveguides 21-1, 21-2, and 21-3 are substantially overlapped with the optical axis of the laser light emitted from the exit of each LD 30. With this configuration and arrangement, the red light, green light, and blue light emitted from the LDs 30-1, 30-2, and 30-3 can be incident on the three optical input side optical waveguides 21-1, 21-2, and 21-3 of the optical multiplexing section 50.

[0080] In the visible light source module 1000, the light exit surface 31 of the LD 30 and the light entrance surface 200A of the light combining member 200 are disposed at a predetermined interval. The light entrance surface 200A faces the light exit surface 31, and there is a gap S between the light exit surface 31 and the light entrance surface 200A in the x direction. Since the visible light source module 1000 is exposed to the air, the gap S is filled with air. Since the gap S is filled with the same gas (air), it is easy to make each color light emitted from the LD 30 enter the entrance path while satisfying a predetermined coupling efficiency. When the visible light source module 1000 is used for AR glasses or VR glasses, the size of the gap (spacing) S in the x direction is, for example, larger than 0 μm and 5 μm or less, taking into account the amount of light required for the AR glasses or VR glasses.

[0081] [Visible Light Source Module (Second Embodiment)] FIG. 10 is a schematic plan view of the visible light source module according to the second embodiment. The visible light source module 2000 shown in Fig. 10 includes the optical multiplexing member 300 with optical modulation function shown in Fig. 8, and a plurality of visible light laser light sources 30 (30-1, 30-2, 30-3) that emit visible light that is multiplexed by the optical multiplexing member 300 with optical modulation function. The optical multiplexing member 300 includes a substrate 10 (see Fig. 4) made of a material different from lithium niobate, an optical multiplexing function layer 20 (see Fig. 4) made of lithium niobate and formed on the main surface of the substrate 10, and has a side surface 300A. Regarding the components shown in FIG. 10, components having the same functions as those described above are given the same reference numerals and the description thereof may be omitted.

[0082] The visible light source module 2000 has three Mach-Zehnder optical waveguides 40-1, 40-2, 40-3, the same number as the number of visible laser light sources 30-1, 30-2, 30-3. The visible laser light sources 30-1, 30-2, 30-3 and the optical input ports 40-1i, 40-2i, 40-3i (see FIG. 8) of the Mach-Zehnder optical waveguides 40-1, 40-2, 40-3 are positioned so that the light emitted from the visible laser light sources is incident on the corresponding Mach-Zehnder optical waveguide.

[0083] The subcarrier 120 on which the visible laser light sources 30-1, 30-2, and 30-3 are mounted and the substrate 10 on which the optical multiplexing function layer 20 having the optical multiplexing member 300 with optical modulation function is formed can be directly bonded via a metal bonding layer. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. In addition, by adjusting the relative positions of the subcarrier 120 and the substrate 10 during manufacturing, the optical axis position of the laser light can be aligned so that the optical axis of each visible light laser coincides with the axis of each input path 43 of the Mach-Zehnder type optical waveguides 40-1, 40-2, and 40-3 (active alignment).

[0084] The size of the optical multiplexing functional layer 20 is, for example, 100 mm 2The size of the optical multiplexing functional layer 20 is 100 mm 2 If it meets the following criteria, it is suitable for use with xR glasses such as AR glasses and VR glasses.

[0085] The optical multiplexing function layer 20 can be manufactured by a known method, for example, by using semiconductor processes such as epitaxial growth, photolithography, etching, vapor phase growth, and metallization.

[0086] When the visible light source module according to the present invention is applied to xR glasses such as AR glasses or VR glasses, the width of the first multimode interference type optical multiplexing section and the second multimode interference type optical multiplexing section constituting the optical multiplexer is preferably, for example, about 1 to 1000 μm, and the length thereof is preferably, for example, about 10 to 10000 μm.

[0087] For example, in a retinal projection display, in order to display an image in a desired color, it is necessary to independently modulate the intensity of each of the three colors of RGB that express visible light at high speed. If such modulation is performed only with a visible light laser light source (current modulation), the load on the IC that controls the modulation will be large, but it is possible to use modulation (voltage modulation) by a Mach-Zehnder type optical modulator 40 (optical multiplexing member 300 with optical modulation function) in combination. In this case, rough adjustment may be performed with a current (visible light laser light source) and fine adjustment with a voltage (Mach-Zehnder type optical modulator 40), or rough adjustment may be performed with a voltage (Mach-Zehnder type optical modulator 40) and fine adjustment with a current (visible light laser light source). Since fine adjustment with voltage has better responsiveness, the former is adopted when responsiveness is important, and since fine adjustment with current requires a lower current and thus reduces power consumption, it is preferable to adopt the latter when reducing power consumption is important.

[0088] [Optical engine] In this specification, an optical engine refers to a device that includes multiple light sources, an optical system including a multiplexing section that combines multiple light beams emitted from the multiple light sources into a single beam of light, an optical scanning mirror that reflects the light emitted from the optical system at a different angle so as to display an image, and a control element that controls the optical scanning mirror.

[0089] 11 is a conceptual diagram for explaining an optical engine 5001 according to this embodiment. The diagram shows a state in which the optical engine 5001 is mounted on a frame 10010 of glasses 10000. Symbol L denotes image display light.

[0090] The optical engine 5001 includes a visible light source module 1001 and a light scanning mirror 3001. As the visible light source module 1001 included in the optical engine 5001, the visible light source module according to the above-described embodiment is used.

[0091] Laser light emitted from a visible light source module 1001 attached to the eyeglass frame is reflected and scanned by a light scanning mirror, enters the human eye, and an image (video) is projected directly onto the retina.

[0092] The optical scanning mirror 3001 is, for example, a MEMS mirror. In order to project a 2D image, it is preferable that the optical scanning mirror 3001 is a two-axis MEMS mirror that vibrates so as to reflect the laser light by changing the angle in the horizontal direction (X direction) and the vertical direction (Y direction).

[0093] The optical engine 5001 has a collimator lens 2001a, a slit 2001b, and an ND filter 2001c as an optical system that optically processes the laser light emitted from the visible light source module 1001. This optical system is just an example, and other configurations may be used.

[0094] The optical engine 5001 includes a laser driver 1100, an optical scanning mirror driver 1200, and a video controller 1300 that controls these drivers. EXAMPLES

[0095] The present invention will be described in more detail below using examples, but the present invention is not limited to the examples shown below.

[0096] Example 1 uses an optical multiplexing member equipped with an MMI type optical multiplexer (three inputs, two outputs type) having the configuration shown in FIG. In Examples 2 and 4 to 8, an optical multiplexing member having an MMI type optical multiplexer (6 inputs, 2 outputs type) having the configuration shown in FIG. 2 is used. The third embodiment is an optical multiplexing member including an MMI type optical multiplexer (9 inputs, 3 outputs type) having the configuration shown in FIG. Comparative Example 1 uses an optical multiplexing member equipped with a 3-input 1-output type MMI optical multiplexer.

[0097] For Examples 1 to 8 and Comparative Example, a configuration was adopted in which the laser light sources were arranged to emit laser light L1, L2, and L3 (see Figs. 2 and 3) in the order of RGB. The laser coupling efficiency in Table 1 was the result of a simulation. Fimmwave (Photon Design) was used as the simulation software. The laser coupling efficiency indicates the proportion of the power of the laser light that was propagated to the optical waveguide on the light input side.

[0098] Each parameter in Table 1 will be described using Example 2 with reference to FIG. 2 and other figures. The number of optical output ports corresponds to the number of optical output ports 22-1o, 22-2o. The distance between the optical output ports at both ends corresponds to the distance indicated by symbol d0 in the figures. The number of optical input ports for one light source corresponds to the number of optical input ports for each of the laser beams L1, L2, and L3. The distance from the laser emission surface to the optical input port corresponds to the gap S shown in FIGS. 9 and 10. The distance between adjacent optical input ports corresponds to the distance indicated by symbol d i The thickness of the slab inside the waveguide was set to be the same as the thickness of the slab outside the waveguide in Examples 1 to 7 and Comparative Example 1 as shown in Fig. 12A, and the thickness of the slab in Example 8 was set to be thicker than the thickness of the slab outside the waveguide as shown in Fig. 12B.

[0099] [Table 1]

[0100] FIG. 13 is a diagram for explaining the relationship between the laser beam diameter corresponding to each embodiment and the distance Z from the laser emission surface (corresponding to the gap S in FIGS. 9 and 10) in the case of a Gaussian beam. The laser beam diameter is defined by the following equation (2).

[0101]

number

[0102] In equations (1) and (2), ω0 is the beam waist (the value at which the beam diameter becomes minimum after diffraction), Z is the distance from the laser light source (corresponding to the gap S in Figs. 9 and 10) (see Fig. 13), and λ is the wavelength of the laser light. Table 2 shows the laser beam diameters [μm] of the RGB laser lights when the beam waist ω0 is 0.2 μm and the distance Z from the laser emission surface is 1 μm, 2.5 μm, and 4 μm. Z=1 μm corresponds to Comparative Example 1 and Example 1, Z=2.5 μm corresponds to Examples 2 and Examples 4 to 8, and Z=4 μm corresponds to Example 3.

[0103] [Table 2]

[0104] From the results shown in Table 1, even when there were two or more optical input ports for each laser light, when the spacing between adjacent optical input ports was 0.5 μm or less (Examples 2 to 6, 8), the coupling efficiency with the laser was 40%, which was sufficiently high compared to 60% when there was one optical input port for each laser light (Example 1, Comparative Example 1). Moreover, Example 8 differs from Example 2 in that the thickness of the slab portion provided on the inside of the optical waveguide on the optical input side is thicker than the thickness of the slab portion provided on the outside of the optical waveguide on the optical input side. Example 8 had a higher coupling efficiency with the laser than Example 2. It was found that such a thickness configuration of the slab portion improves the coupling efficiency with the laser.

[0105] Example 1 has two optical output ports, and is configured to guide the light from the optical multiplexing unit to the optical output port using two optical output-side optical waveguides according to the number of optical output ports. Therefore, compared to the comparative example having one optical output port and one optical output-side optical waveguide guiding the light from the optical multiplexing unit to the optical output port, the power density of the laser light is distributed to two optical output-side optical waveguides while maintaining the same coupling efficiency with the laser (60%), making it possible to suppress deterioration of the optical output-side optical waveguide compared to the comparative example. Therefore, Example 1 is also suitable as an optical multiplexer for high-power lasers. Examples 2, 4 to 8 are configured to have two optical output ports, and guide the light from the optical multiplexing unit to the optical output port by two optical output side optical waveguides according to the number of the optical output ports. Therefore, compared to the comparative example having one optical output port and guiding the light from the optical multiplexing unit to the optical output port by one optical output side optical waveguide, the power density of the laser light is distributed to two optical output side optical waveguides without a significant decrease in coupling efficiency with the laser (60% in the comparative example, whereas 30% to 50% in Examples 2, 4 to 8). Furthermore, Examples 2, 4 to 8 are configured to have two optical input ports for each laser light source, and guide each laser light incident on the two optical input ports for each laser light source to the optical multiplexing unit by two optical input side optical waveguides, and the power density of each laser light is distributed to two optical input side optical waveguides, and therefore it is possible to suppress deterioration of the optical input side optical waveguide compared to the comparative example. Therefore, Examples 2 and 4 to 8 are also suitable as optical multiplexers for high-output lasers. Example 3 has three optical output ports, and is configured to guide the light from the optical multiplexing unit to the optical output port through three optical output side optical waveguides according to the number of optical output ports. Therefore, compared to the comparative example having one optical output port and one optical output side optical waveguide guiding the light from the optical multiplexing unit to the optical output port, the power density of the laser light is distributed to three optical output side optical waveguides without a significant decrease in coupling efficiency with the laser (60% in the comparative example and 40% in Example 3), and it is possible to suppress deterioration of the optical output side optical waveguide compared to the comparative example. Furthermore, Example 3 has three optical input ports for each laser light source, and each laser light incident on the three optical input ports for each laser light source is guided to the optical multiplexing unit through three optical input side optical waveguides, and the power density of each laser light is distributed to three optical input side optical waveguides, so it is possible to suppress deterioration of the optical input side optical waveguide compared to the comparative example. Therefore, Example 3 is also suitable as an optical multiplexer for high-power lasers. [Explanation of symbols]

[0106] 10 Substrate 20 Optical multiplexing functional layer 30 Visible light laser source 40 Mach-Zehnder type optical modulator 50, 51, 52 Optical multiplexing section 100, 101, 102 optical multiplexer 200, 300 Optical multiplexing member 1000 2000 Visible light source module

Claims

1. An optical multiplexer that multiplexes a plurality of laser beams having different wavelengths, a plurality of optical input ports into which the plurality of laser beams can respectively be input; two or more optical output ports capable of multiplexing and outputting the plurality of laser beams; a plurality of optical input side optical waveguides extending from the plurality of optical input ports, respectively; Two or more optical output side optical waveguides extending from the two or more optical output ports, respectively; an optical multiplexing section to which the plurality of optical input side optical waveguides and the two or more optical output side optical waveguides are connected.

2. 2. The optical multiplexer according to claim 1, wherein the plurality of optical input ports include two or more optical input ports for at least one laser light.

3. 3. The optical multiplexer according to claim 2, wherein said plurality of optical input ports comprises two or more optical input ports for each of all laser lights.

4. 2. The optical multiplexer according to claim 1, wherein the distance between the most distant optical output ports among said two or more optical output ports is 25 [mu]m or less.

5. 3. The optical multiplexer according to claim 2, wherein, of the two or more optical input ports provided for one laser beam, the interval between adjacent optical input ports is 0.5 [mu]m or less.

6. 2. The optical multiplexer according to claim 1, wherein a thickness of the slab portion provided on the inner side of said optical input side waveguide is greater than a thickness of a slab portion provided on the outer side of said optical input side waveguide.

7. 2. The optical multiplexer according to claim 1, wherein the optical multiplexer is a multimode interference type multiplexer.

8. a substrate made of a material different from lithium niobate; a light-multiplexing functional layer formed on a main surface of the substrate and made of a lithium niobate film; An optical multiplexing member, comprising an optical multiplexer according to any one of claims 1 to 7 formed in an optical multiplexing functional layer.

9. 9. A visible light source module comprising: the optical multiplexer according to claim 8; and a plurality of visible laser light sources that emit visible laser beams multiplexed by the optical multiplexer.

10. 9. An optical multiplexing member with an optical modulation function, comprising a Mach-Zehnder type optical modulator in the optical multiplexing functional layer of the optical multiplexing member according to claim 8.

11. 11. A visible light source module comprising: the optical multiplexer with optical modulation function according to claim 10; and a plurality of visible laser light sources that emit visible laser beams multiplexed by the optical multiplexer with optical modulation function.

12. A visible light source module according to claim 9 ; an optical scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image;

13. A visible light source module according to claim 11; an optical scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image;

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