Optical multiplexer, optical multiplexing member with optical modulation function, visible light light source module, optical engine, and xr glass

Abstract

To provide an optical multiplexer which is connectable to or can be integrated with an optical modulator using a lithium niobate film, and which can be more downsized than before.SOLUTION: An optical multiplexer 100 according to the present invention multiplexes a plurality of laser beams differing in wavelength, and comprises an optical multiplexing unit 50, a plurality of optical input-side optical waveguides 21-1, 21-2, 21-3 connecting thereto, and one optical output-side optical waveguide 22T connecting to the optical multiplexing unit 50, with the optical multiplexing unit 50 composed of one stage or multiple stages of MMI-type optical multiplexing units. The optical input-side optical waveguides 21-1, 21-2, 21-3 have a trapezoidal cross section, and the optical multiplexing unit 50 and the optical output-side optical waveguide 22T have a trapezoidal or a rectangular cross section. The lower side internal angles α21, α22 of the trapezoidal or a rectangular cross section of the optical multiplexing unit 50 and the optical output-side optical waveguide 22T are larger than at least one of the two lower side internal angles α11, α12 of the trapezoidal cross section of the optical input-side optical waveguides 21-1, 21-2, 21-3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Glasses-type devices are currently being considered for VR and AR. In particular, retinal scanning displays, which allow users to view images by focusing two-dimensionally scanned light on the user's retina, have been attracting attention in recent years. In retinal scanning displays, three colors of visible light, typically R (red), G (green), and B (blue), are emitted from light sources such as LEDs (Light Emitting Diodes) or LDs (Laser Diodes) and are combined on a single optical axis. The combined three colors of visible light are transmitted to an image display unit. The image display unit then two-dimensionally scans the transmitted light and makes it incident on the user's pupil. The user views the image when this incident light forms an image on the user's retina.

[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] Japanese Patent Application Laid-Open No. 2012-48071 [Patent Document 5] Japanese Patent Publication No. 2020-27170 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 placed close to each other at the exit section, but they are not combined, so the optical axis for each wavelength is different, making it difficult to control the emitted light.

[0006] Furthermore, there is a demand for an optical multiplexer that can be connected to or integrated with a visible light modulator and that can adjust the RGB color balance, but this has not yet been considered.

[0007] However, in Patent Document 1, the light beams are simply placed close to each other at the exit section, without being multiplexed. As a result, the optical axes of the light beams differ for each wavelength, making it difficult to control the emitted light.

[0008] Furthermore, Patent Document 2 discloses a visible light modulator using a lithium niobate film. 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.

[0009] Directional couplers are generally considered for combining visible light (see, for example, 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.

[0010] Patent Documents 4 and 5 disclose the configuration of an RGB multiplexer using an MMI (multimode interferometer), but both use glass-based materials, and do not disclose any configuration using a lithium niobate film. An MMI 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 multiplexed and output as the output signal. An MMI optical multiplexer is an optical multiplexer that utilizes the property that, for each wavelength, multiple modes generated within the wide optical multiplexer interfere with each other and form an image (converge) at a specific position.

[0011] The present invention has been made in view of the above-mentioned problems, and aims to provide an optical multiplexer, a visible light source module, and an optical engine that can be connected to or integrated with an optical modulator using a lithium niobate film, and that are smaller than conventional ones and have reduced optical loss. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides the following means.

[0013] A first aspect of the present invention is an optical multiplexer that multiplexes laser light of multiple different wavelengths, comprising an optical multiplexing section, a plurality of optical input side optical waveguides connected to the optical multiplexing section, and one optical output side optical waveguide connected to the optical multiplexing section, wherein the optical multiplexing section is made up of a single or multiple stage MMI type optical multiplexing section, the optical input side optical waveguide has a trapezoidal cross section, the optical multiplexing section and the optical output side optical waveguide have trapezoidal or rectangular cross sections, and a lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section and the optical output side optical waveguide is larger than at least one of two lower interior angles of the trapezoidal cross section of the optical input side optical waveguide.

[0014] A second aspect of the present invention is an optical multiplexer according to the first aspect, wherein the lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section and the optical output side optical waveguide is 80° or more and 90° or less, and the lower interior angle of the trapezoidal cross section of the optical input side optical waveguide is 65° or more and less than 80°.

[0015] A third aspect of the present invention is an optical multiplexer according to the first or second aspect, wherein the one-stage or multi-stage MMI optical multiplexing sections are each a 3×1 type MMI optical multiplexing section or a 2×1 type MMI optical multiplexing section.

[0016] A fourth aspect of the present invention is an optical multiplexer according to the first or second aspect, wherein at least one of the one-stage or multiple-stage MMI type optical multiplexing sections is an MMI-coupled optical multiplexing section formed by coupling a first MMI type optical multiplexing element and a second MMI type optical multiplexing element from the input side, and the width of the first MMI type optical multiplexing element is wider than the width of the second MMI type optical multiplexing element.

[0017] A fifth aspect of the present invention is the optical multiplexer according to any one of the first to fourth aspects, wherein the plurality of different wavelengths are all visible light wavelengths.

[0018] A sixth aspect of the present invention is an optical multiplexing element in which the optical multiplexer of any one of the first to fifth aspects comprises a substrate made of a material different from lithium niobate and a lithium niobate film formed on a main surface of the substrate, and the optical multiplexer of any one of the first to fifth aspects is formed on the lithium niobate film.

[0019] A seventh aspect of the present invention is a visible light source module including the optical multiplexing member of the sixth aspect and a plurality of visible laser light sources that emit visible light multiplexed by the optical multiplexing member.

[0020] An eighth aspect of the present invention is an optical multiplexing member with an optical modulation function, comprising the optical multiplexing member of the sixth aspect and a Mach-Zehnder optical modulator connected to the optical multiplexing member and guiding multiple visible light beams emitted from multiple visible light laser light sources to the optical multiplexer.

[0021] A ninth aspect of the present invention is a visible light source module including the optical multiplexer with optical modulation function of the eighth aspect, and a plurality of visible laser light sources that emit visible light to be multiplexed by the optical multiplexer with optical modulation function.

[0022] A tenth aspect of the present invention is an optical engine including the visible light source module of the seventh aspect, and a light scanning mirror that reflects light emitted from the visible light source module at different angles so as to display an image.

[0023] An eleventh 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 light emitted from the visible light source module at different angles so as to display an image.

[0024] A twelfth embodiment of the present invention is XR glasses equipped with the optical engine of the tenth embodiment.

[0025] A thirteenth aspect of the present invention is XR glasses equipped with the optical engine of the eleventh aspect. [Effects of the Invention]

[0026] 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 is smaller in size than conventional optical multiplexers and has reduced optical loss. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a plan view schematically illustrating a configuration including a three-input, one-output, one-stage MMI-coupled optical multiplexing section as an example of an optical multiplexer according to an embodiment. [Figure 2A] FIG. 2 is a schematic cross-sectional view showing a cross section of a light input side optical waveguide. [Figure 2B] 3 is a cross-sectional view schematically illustrating a cross section of an optical multiplexing section and an optical waveguide on a light output side. FIG. [Figure 3A] 2A and 2B are schematic cross-sectional views showing examples of cross sections of the light input side optical waveguides 21-1, 21-2, and 21-3. [Figure 3B] 2A and 2B are schematic cross-sectional views showing examples of cross sections of the light input side optical waveguides 21-1, 21-2, and 21-3. [Figure 4A] 3 is a schematic cross-sectional view showing an example of a cross section of an optical multiplexing section and an optical output-side optical waveguide. FIG. [Figure 4B] 3 is a schematic cross-sectional view showing an example of a cross section of an optical multiplexing section and an optical output-side optical waveguide. FIG. [Figure 4C] 3 is a schematic cross-sectional view showing an example of a cross section of an optical multiplexing section and an optical output-side optical waveguide. FIG. [Figure 5A]10 is a cross-sectional view schematically illustrating an example of a combination of cross sections of a plurality of optical input side optical waveguides. FIG. [Figure 5B] FIG. 2 is a cross-sectional view showing an example of a cross section of a first MMI type optical multiplexing element. [Figure 5C] FIG. 2 is a cross-sectional view showing an example of a cross section of a second MMI type optical multiplexing element. [Figure 5D] FIG. 2 is a schematic cross-sectional view showing an example of a cross section of a light output side optical waveguide. [Figure 6] FIG. 10 is a schematic plan view of a two-input type optical multiplexer as another example of the optical multiplexer according to the embodiment. [Figure 7A] FIG. 1 is a diagram for explaining the principle of an MMI optical multiplexer, and is a conceptual diagram showing the relationship between the width WM and effective width We of the optical multiplexer and the single mode and higher-order modes. [Figure 7B] FIG. 1 is a diagram for explaining the principle of an MMI optical multiplexer, and is a diagram showing simulation results of electromagnetic field distribution in the cross section of each waveguide for a single mode (TM0), a higher-order mode (TM1), and a higher-order mode (TM2). [Figure 8A] FIG. 1 is a diagram for explaining the principle of an MMI optical multiplexer, showing the results of a simulation of the electromagnetic field distribution of red (R) light. [Figure 8B] 1 is a diagram for explaining the principle of an MMI optical multiplexer, showing the results of a simulation of the electromagnetic field distribution of green (G) light. [Figure 9A] 10 is a graph showing the relationship between the lengths and beat length of the first MMI type optical multiplexing element and the second MMI type optical multiplexing element and the output intensity for each of red (R) laser beams. [Figure 9B] 10 is a graph showing the relationship between the lengths and beat length of the first MMI type optical multiplexing element and the second MMI type optical multiplexing element and the output intensity for each of green (G) laser beams. [Figure 10A] 1 is a conceptual diagram illustrating an MMI single-type optical multiplexing unit according to this embodiment. [Figure 10B] 1 is a conceptual diagram showing an MMI-coupled optical multiplexing section formed by coupling two optical multiplexing elements according to this embodiment. [Figure 11A] This is an example of a single-stage 3x1 MMI type optical multiplexing section provided in the optical multiplexer. [Figure 11B] This is an example of a single-stage 2x1 MMI type optical multiplexing section provided in the optical multiplexer. [Figure 11C] The MMI type optical multiplexing section included in the optical multiplexer is another example of a single-stage 2×1 MMI single type optical multiplexing section. [Figure 11D] The MMI type optical multiplexing section provided in the optical multiplexer is an example of a two-stage MMI-linked optical multiplexing section. [Figure 12A] 2 is a cross-sectional view of an optical multiplexer in which the components shown in FIG. 1 are formed on a lithium niobate film, taken along line XX' in FIG. 1. [Figure 12B] 7 is a cross-sectional view of an optical multiplexer in which the components shown in FIG. 6 are formed on a lithium niobate film, taken along line XX' in FIG. 2. [Figure 13] FIG. 10 is a schematic cross-sectional view taken along the YZ plane when the cross section of the MMI type optical multiplexing section is trapezoidal and has a slab section on the substrate side. [Figure 14] 1 is a schematic plan view of an optical multiplexing member with optical modulation function according to an embodiment of the present invention; [Figure 15] 1 is a schematic plan view of a visible light source module according to a first embodiment. [Figure 16] 16 is a schematic cross-sectional view of a part of the light source module shown in FIG. 15 cut along the XZ plane, depicting only a part near the joint. [Figure 17A] FIG. 10 is a diagram for explaining an example of a method for driving an optical modulator. [Figure 17B] 10A and 10B are diagrams for explaining another example of a method for driving an optical modulator. [Figure 17C] 10A and 10B are diagrams for explaining another example of a method for driving an optical modulator. [Figure 18] FIG. 10 is a schematic plan view of a visible light source module according to a second embodiment. [Figure 19] FIG. 1 is a conceptual diagram for explaining an example of the XR glasses of the present invention. [Figure 20]FIG. 20 is a conceptual diagram showing how an image is projected directly onto the retina by laser light emitted from a light source module in the XR glasses shown in FIG. 19. [Figure 21] FIG. 1 is a cross-sectional schematic diagram showing a model of a three-input, one-output, single-stage MMI-coupled optical multiplexer used in the simulation. [Figure 22] FIG. 1 is a cross-sectional schematic diagram showing a model of a two-input, one-output, single-stage MMI single-type optical multiplexer used in the simulation. DETAILED DESCRIPTION OF THE INVENTION

[0028] 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 portions enlarged for convenience in order to make the features 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. Appropriate changes can be made within the scope of the effects of the present invention.

[0029] [Optical multiplexer] Fig. 1 is a plan view showing a three-input type as an example of an optical multiplexer according to an embodiment. Fig. 2A is a cross-sectional view showing a cross section of an optical input waveguide, and Fig. 2B is a cross-sectional view showing a cross section of an optical multiplexing section and an optical output waveguide. Here, the cross sections of the optical input waveguide, the optical multiplexing section, and the optical output waveguide refer to cross sections perpendicular to the light propagation direction (X direction in Fig. 1).

[0030] The optical multiplexer according to this embodiment is a multi-mode interference (MMI) type optical multiplexer. In this specification, an optical multiplexing unit formed by coupling parts of different sizes (rectangular parts in plan view) as shown in Figure 1 may be referred to as an "MMI coupled optical multiplexing unit." The parts (rectangular parts in plan view) that constitute an MMI coupled optical multiplexing unit are referred to as "optical multiplexing elements." In contrast, an optical multiplexing unit consisting of a single rectangular part may be referred to as an "MMI single type optical multiplexing unit." An MMI single type optical multiplexing unit consists of a single optical multiplexing element. An MMI coupled optical multiplexing unit and an MMI single type optical multiplexing unit may be collectively referred to as an MMI type optical multiplexing unit. Furthermore, an optical multiplexer in which MMI single-type optical multiplexers or MMI coupled-type optical multiplexers are connected via optical waveguides may be referred to as an "MMI coupled-type optical multiplexer." Furthermore, with regard to the "MMI coupled-type optical multiplexer," depending on the number of optical waveguides connected, a configuration in which two MMI single-type optical multiplexers or MMI coupled-type optical multiplexers are connected may be referred to as a two-stage MMI coupled-type optical multiplexer (or simply, a two-stage MMI optical multiplexer), a configuration in which three are connected may be referred to as a three-stage coupled-type optical multiplexer (or simply, a three-stage MMI optical multiplexer), and a configuration in which multiple units are connected may be referred to as a multi-stage coupled-type optical multiplexer (or simply, a multi-stage MMI optical multiplexer). Configurations in which no coupling occurs may be referred to as a single-stage MMI single-type optical multiplexer or a single-stage MMI coupled-type optical multiplexer. The single-stage MMI single-type optical multiplexer and the single-stage MMI coupled-type optical multiplexer are sometimes collectively referred to as a single-stage MMI type optical multiplexer.

[0031] The optical multiplexer 100 shown in FIG. 1 has a configuration including a single-stage MMI-coupled optical multiplexing section of a three-input one-output type (3×1 type). The optical multiplexer 100 shown in FIG. 1 is an optical multiplexer that multiplexes laser light of three different wavelengths, and includes an optical multiplexing section 50, three optical input side optical waveguides 21-1, 21-2, and 21-3 connected to the optical multiplexing section 50, and one optical output side optical waveguide 22T connected to the optical multiplexing section 50. The optical multiplexing section 50 is connected from the optical input side to a first MMI type optical multiplexing element 50-1 and a second MMI type optical multiplexing element 50-2. a width W1 of the first MMI type optical multiplexing element 50-1 is wider than a width W2 of the second MMI type optical multiplexing element 50-2; the optical input side optical waveguides 21-1, 21-2, and 21-3 have trapezoidal cross sections; the optical multiplexing section 50 and the optical output side optical waveguide 22T have trapezoidal or rectangular cross sections; and a lower interior angle α of the trapezoidal or rectangular cross sections of the optical multiplexing section 50 and the optical output side optical waveguide 22T 21 , α 22 At least one of the two lower interior angles of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3 is a lower interior angle α 11 , α 12 is greater than. Here, when the cross section of the optical input side optical waveguide, the cross section of the optical multiplexing section, and the cross section of the optical output side optical waveguide are trapezoidal, this refers to a trapezoid whose upper base is shorter than its lower base, and the lower interior angle refers to the angle between the lower base and an inclined line extending from one end of the lower base to one end of the upper base. A rectangular cross section is a figure in which all interior angles are 90 degrees, and therefore the two lower interior angles are both 90 degrees. The optical waveguide may have a tapered shape in which the width increases continuously from a predetermined position of the optical waveguide to the point where the optical waveguide is connected to the MMI optical multiplexing element, allowing a defined inclination angle, as in the models employed in the examples described below. For example, if the width of the top surface of the optical waveguide where the laser light is incident is 0.3 to 1.2 μm, the tapered portion having this tapered shape may have a starting width of 0.3 to 1.2 μm, a width of the portion where the optical waveguide is connected to the MMI optical multiplexing element may be, for example, 0.5 to 2.5 μm, and a length of 10 to 500 μm.

[0032] In FIG. 1, A1-A1', A2-A2', A3-A3', and A4-A4' respectively indicate examples of the positions of the cross section of the optical input side optical waveguide, the cross section of the first MMI type optical multiplexing element, the cross section of the second MMI type optical multiplexing element, and the cross section of the optical output side optical waveguide.

[0033] It was found that in an optical multiplexer in which the cross sections of the optical input side optical waveguide, the optical multiplexing section, and the optical output side optical waveguide are designed to be trapezoidal with the same lower interior angle, the length in the direction of light propagation becomes long, and it is not easy to obtain a small optical multiplexer with reduced optical loss. Therefore, the optical multiplexer of this embodiment is configured so that the lower interior angles of the trapezoidal cross sections of the optical multiplexing section and the optical output side optical waveguide are larger than the lower interior angles of at least one of the trapezoidal cross sections of the optical input side optical waveguide, thereby suppressing optical loss and achieving miniaturization. In the optical multiplexer of this embodiment, even if the distance between adjacent optical input side optical waveguides is about 10 μm or less, an optical multiplexer in which optical loss is suppressed can be realized.

[0034] The lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T 21 , α 22 The angle can be set to 80° or more and 90° or less. This configuration makes it possible to reduce the size while suppressing optical loss. In addition, the lower interior angle α of the trapezoidal cross section of the optical multiplexing unit 50 21 , α 22 is preferably 80° or more and 85° or less, and the lower interior angle of the trapezoidal or rectangular cross section of the light output side optical waveguide 22T is preferably 85° or more and 90° or less.

[0035] At least one lower interior angle α of the trapezoidal cross section of the optical input side optical waveguides 21-1, 21-2, and 21-3 11 , α 12 can be greater than or equal to 65° and less than 80°. 11 , α 12 The angle may be 70° or more and less than 80°, or 70° or more and 78° or less. This configuration makes it possible to reduce the size while suppressing optical loss.

[0036] If the cross sections of the optical input side optical waveguide, the optical multiplexing section, and the optical output side optical waveguide are all rectangular, peeling or cracking is likely to occur from the substrate or slab, which may result in propagation loss and coupling loss in the optical multiplexing section due to light scattering, etc. In contrast, in the optical multiplexer of this embodiment, the cross sections of at least a portion of the optical input side optical waveguide, the optical multiplexing section, and the optical output side optical waveguide are trapezoidal, so peeling or cracking is less likely to occur, and as a result, propagation loss and coupling loss in the optical multiplexing section are suppressed.

[0037] In the optical multiplexer 100 shown in FIG. 1, the two lower interior angles α of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3 are 11 , α 12 are the same angle as shown in FIG. 2A, but may be different angles. FIG. 3A shows the two lower interior angles α of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3. 11 , α 12 are different, and α 11 >α 12 In the following, the two lower interior angles α of the trapezoidal cross section are 11 , α 12 When these are the same, it is called a symmetric trapezoid, and when they are different, it is called an asymmetric trapezoid. 3B shows the relationship between the two lower interior angles α of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3. 11 , α 12 are different, and α 11 >α 12 and α 12 is 90°. The two lower interior angles α of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3 11 , α 12 may be different from each other, or some lower interior angles may be the same and other lower interior angles may be different.

[0038] Similarly, in the optical multiplexer 100 shown in FIG. 1, the lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T is 21 , α 22are the same angle as shown in FIG. 2B, but may be different angles. 4A shows the lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T. 21 , α 22 are different, and α 21 >α 22 This is the case. 4B shows the lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T. 21 , α 22 are different, and α 21 >α 22 and α 22 is 90°. 4C shows the lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T. 21 , α 22 is the same, and α 21 and α 22 are both 90°. The lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T 21 , α 22 may be different from each other, or some lower interior angles may be the same and other lower interior angles may be different.

[0039] FIG. 5A is a cross-sectional view showing an example of a combination of cross sections of the light input side optical waveguides 21-1, 21-2, and 21-3 taken along the line A1-A1' in FIG. The optical input side optical waveguide 21-2 has two lower interior angles α 11 , α 12 In both cases, the lower interior angle α of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T is 21 , α 22 (see FIG. 2), and the optical input side optical waveguides 21-1 and 21-3 have two lower interior angles α 11 , α 12 In this case, the lower interior angle on the side farther from the light input side optical waveguide 21-2 is 90° (see FIG. 3B).

[0040] In the cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3 shown in FIG. 5, the optical input side optical waveguide 21-2 is a symmetric trapezoid, and the optical input side optical waveguide 21-1 and the optical input side optical waveguide 21-3 are asymmetric trapezoids. The lower interior angle of the optical input side optical waveguide 21-2 can be, for example, 76±3°, and the lower interior angle of the optical input side optical waveguide 21-1 and the optical input side optical waveguide 21-3 that is not 90° can be, for example, 70±3°. The optical input side optical waveguide, the optical multiplexing section, and the optical output side optical waveguide can be formed by ion milling, and the size of the lower interior angle of the cross section of the optical input side optical waveguides 21-1, 21-2, and 21-3 can be adjusted by adjusting the incident angle of ions (e.g., Ar ions) in the ion milling. The distance between adjacent optical input side optical waveguides can be set to about 0.5 to 3.0 μm.

[0041] 5B to 5D are schematic cross-sectional views showing an example of a cross section of the first MMI type optical multiplexing element 50-1 taken along the line A2-A2' in FIG. 1, a cross section of the second MMI type optical multiplexing element 50-2 taken along the line A3-A3', and a cross section of the optical output side optical waveguide 22T, respectively, and these cross sections can be used in combination.

[0042] The first MMI type optical multiplexing element 50-1 shown in FIG. 5B and the second MMI type optical multiplexing element 50-2 shown in FIG. 5C are both formed by the trapezoidal cross section with two lower interior angles α 21 , α 22 have the same symmetrical trapezoidal cross section, and in this example, both the first MMI type optical multiplexing element 50-1 and the second MMI type optical multiplexing element 50-2 have the same lower interior angle. The lower interior angle of the first MMI type optical multiplexing element 50-1 and the second MMI type optical multiplexing element 50-2 can be set to, for example, 83±3°.

[0043] In addition, the optical output side optical waveguide 22T shown in FIG. 5D has two lower interior angles α 21 , α 22 have the same symmetrical trapezoidal cross section. The lower interior angle of the light output side optical waveguide 22T can be set to, for example, 88±2°.

[0044] Furthermore, the combination of the cross sections of the optical input side optical waveguides 21-1, 21-2, and 21-3 shown in FIG. 5A may be further combined with the combination of the cross sections of the first MMI type optical multiplexing element 50-1, the second MMI type optical multiplexing element 50-2, and the optical output side optical waveguide 22T shown in FIGS. 5B to 5D.

[0045] 1 is a 3x1 multi-mode interference (MMI) type optical multiplexer formed by combining two optical multiplexing elements. The laser light multiplexed by the optical multiplexer 100 can be, for example, three different laser lights of RGB. In FIG. 1, the X direction is a direction perpendicular to the side surface on which the light entrance is located, the Y direction is a direction perpendicular to the X direction, and the Z direction is a direction perpendicular to the plane formed by the X and Y directions.

[0046] The first MMI type optical multiplexing element 50-1 has connected to its optical input side an optical waveguide 21-1, an optical input side optical waveguide 21-2, and an optical input side optical waveguide 21-3 that are connected to three optical input ports (first optical input port 21-1i, second optical input port 21-2i, third optical input port 21-3i) provided on the first side surface 100A, respectively. On the other hand, the second MMI type optical multiplexing element 50-2 has, on its optical output side, an optical output side optical waveguide 22T connected to one optical exit port 22To.

[0047] 1 has three input ports corresponding to the three different wavelengths of laser light to be input, but the number is not limited to three and may be two or four or more input ports. Accordingly, the two-stage optical multiplexing section 50 may be a 2×1 MMI type optical multiplexing section, a 4×1 MMI type optical multiplexing section, or an MMI type optical multiplexing section where the number of input ports is an integer greater than or equal to 5×1, in addition to a 3×1 MMI type optical multiplexing section.

[0048] The three wavelengths may be different wavelengths of visible light.

[0049] At least one lower interior angle of the trapezoidal cross section of each of the optical input side optical waveguides 21-1, 21-2, and 21-3 can be 65° or more and less than 80°. The lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section 50 and the optical output side optical waveguide 22T can be 80° or more and 90° or less.

[0050] FIG. 6 is a schematic plan view showing an optical multiplexer having a two-input one-output (2×1) type one-stage MMI coupling type optical multiplexing section, as another example of the optical multiplexer according to this embodiment. The optical multiplexer 110 shown in FIG. 6 is an optical multiplexer that multiplexes laser light of two different wavelengths, and includes an optical multiplexing section 150, two optical input side optical waveguides 121-1 and 121-2 connected to the optical multiplexing section 150, and one optical output side optical waveguide 122T connected to the optical multiplexing section 150. The optical multiplexing section 150 is an MMI coupled optical multiplexing section in which a first MMI type optical multiplexing element 150-1 and a second MMI type optical multiplexing element 150-2 are connected from the input side. a width W1 of the first MMI type optical multiplexing element 150-1 is wider than a width W2 of the second MMI type optical multiplexing element 150-2; the optical input side optical waveguides 121-1 and 121-2 have trapezoidal cross sections; the optical multiplexing section 150 (150-1 and 150-2) and the optical output side optical waveguide 122T have trapezoidal or rectangular cross sections; and a lower interior angle α of the trapezoidal or rectangular cross sections of the optical multiplexing section 150 (150-1 and 150-2) and the optical output side optical waveguide 122T 21 , α 22 is at least one of the two lower interior angles α of the trapezoidal cross sections of the optical input side optical waveguides 121-1 and 121-2. 11 , α 12 is greater than.

[0051] The first MMI type optical multiplexing element 150-1 has, on its optical input side, an optical input side optical waveguide 121-1 and an optical input side optical waveguide 121-2 connected to two optical input ports (first optical input port 121-1i, second optical input port 21-2i) provided on the first side surface 110A. On the other hand, the second MMI type optical multiplexing element 150-2 has, on its optical output side, an optical output side optical waveguide 122 connected to one optical exit port 122o.

[0052] The principle of the MMI type optical multiplexer will be explained with reference to FIGS. 7A, 7B, 8A, and 8B. FIG. 7A shows the width W M Figure 7 shows the single mode (v = 0) and higher-order modes (v ≥ 1) generated in the waveguide. We is the effective width of the MMI optical multiplexer, and is approximated by the effective width of the MMI optical multiplexer taking into account the optical mode bleeding and Goos-Henschen shift in the zeroth-order mode (fundamental mode). Figure 7B shows the simulation results of the electromagnetic field distribution in the cross section of the waveguide for the single mode (TM0), higher-order mode (TM1), and higher-order mode (TM2).

[0053] In an MMI optical multiplexer, multiple modes from the zeroth-order mode to higher-order modes interfere with each other and are characterized by forming an image (converging) at a specific position (a specified distance from the input end) of the MMI optical multiplexer. It is known that the distance or period (beat length) Lπ between adjacent convergence points roughly follows equation (1). Equation (1) is the beat length Lπ between the two lower-order modes, the zeroth-order mode and the first-order mode.

[0054]

number

[0055] In equation (1), We is the effective width of the MMI optical multiplexer, n is the effective refractive index of the MMI, and λ is the wavelength of the input light. β0 and β1 are the propagation constants of the zeroth and first modes, respectively. From equation (1), we can see that the beat length depends on the width and wavelength of the MMI optical multiplexer.

[0056] When the electromagnetic field distribution undergoes a phase shift of 2π in all propagation modes generated within the MMI optical multiplexer, the optical intensity distribution coincides with the incident optical intensity distribution. The optical propagation distance required to achieve this coincidence (convergence) state is called the self-projection distance, and convergence is repeated at a period of Lπ after a certain propagation distance of 3Lπ / 4.

[0057] Figures 8A and 8B show the results of a simulation using simulation software (Photon Design's Fimmwave) of the electromagnetic field distribution at a cross section of a 2 × 1 MMI optical coupler (R / G coupler) along the light propagation direction (x direction). In the simulation model, the y-axis coordinate of the input waveguide where red (R) light with a wavelength of 638 nm enters the optical coupler is the same as the y-axis coordinate of the output waveguide of the optical coupler, while the y-axis coordinate of the input waveguide where green (G) light with a wavelength of 520 nm enters the optical coupler is separated by a predetermined distance. Lighter colors indicate areas where the modes interfere more strongly ("strong" in the figure), darker colors indicate areas where the modes do not interfere more strongly ("weak" in the figure), and intermediate colors indicate areas where the degree of interference between the modes is intermediate ("middle" in the figure).

[0058] FIG. 8A shows the results of a simulation of the electromagnetic field distribution of red (R) light, and FIG. 8B shows the results of a simulation of the electromagnetic field distribution of green (G) light. 8A and 8B, there is a strong interference portion near the output port of the optical multiplexer, and it is preferable to set the length (length in the X direction) of the MMI optical multiplexer so that this position coincides as closely as possible (i.e., so that it is as close as possible to an integer multiple (least common multiple) of the beat length of each input wavelength). However, because of the influence of the phase difference depending on the input position of each input wavelength to the optical multiplexer, the length of the MMI optical multiplexer cannot be determined solely by an integer multiple of the beat length of each input wavelength. Therefore, the length of the optical multiplexer should be set to an integer multiple (least common multiple) of the beat length of each input wavelength, and should be adjusted taking into account the phase effect of the input position of each input wavelength into the optical multiplexer.

[0059] 9A and 9B are graphs showing the relationship between the lengths and beat lengths of the first MMI optical multiplexing element (first stage) and the second MMI optical multiplexing element (second stage) and the output intensity for red (R) and green (G) laser light, respectively. The horizontal axis represents the length (L1, L2) of the MMI optical multiplexing section, and the vertical axis represents the optical intensity.

[0060] The beat lengths of red (R) and green (G) are different. If the lengths of the first MMI type optical multiplexing element and the second MMI type optical multiplexing element are approximately 700 μm, both red (R) and green (G) can be multiplexed with an output intensity of 0.3.

[0061] FIG. 10A conceptually shows an MMI single-type optical multiplexing unit, and FIG. 10B conceptually shows an MMI coupled-type optical multiplexing unit in which two optical multiplexing elements are coupled. FIG. 10A shows an MMI optical multiplexer equipped with one MMI optical multiplexing section A50, and FIG. 10B shows an MMI coupled optical multiplexing section 50 in which a wide first MMI optical multiplexing element 50-1 and a narrow second MMI optical multiplexing element 50-2 are connected from the input side. The waves in the optical multiplexer conceptually represent the interference period (beat length), and from equation (1) above, the interference period (beat length) is proportional to the square of the width of the optical multiplexer for each wavelength. Therefore, the waves in the optical multiplexer shown in Figure 6 conceptually represent the fact that, for each wavelength, the wider the width of the optical multiplexer, the longer the beat length (beat period), and the narrower the width, the shorter the beat length (beat period). The shorter the beat length of each wavelength, the shorter the distance that is an integer multiple (least common multiple) of the beat length, making it possible to shorten the length of the MMI-type optical multiplexer.

[0062] As shown in FIG. 10B, in the optical multiplexer according to this embodiment, by making the width (y direction) of the subsequent MMI type optical multiplexer in the MMI coupled optical multiplexer section narrower than the width (y direction) of the MMI type optical multiplexer on the input side, the beat length in the subsequent MMI type multiplexer section is shortened, and the overall size of the optical multiplexer can be reduced.

[0063] Here, the subsequent MMI type optical multiplexing unit only needs to have one output port, but the width of the input-side MMI type optical multiplexing unit needs to be provided with multiple input ports, so it cannot be made as narrow as the subsequent MMI type optical multiplexing unit. For example, when mounted on a glasses-type terminal, it is preferable that the width of the MMI type optical multiplexer on the input side is 1.9 μm or more, in view of current processing technology. In the optical multiplexer of the present invention, the length of the MMI type optical multiplexing section can be set to about 300 to 1000 μm, and the length of the entire optical multiplexer can be set to about 400 to 1100 μm.

[0064] The MMI type optical multiplexing sections included in the optical multiplexers shown in FIGS. 1 and 6 are both examples of single-stage MMI coupling type optical multiplexing sections. 11A to 11D are schematic plan views of examples of MMI-type optical multiplexing units having configurations other than a single-stage MMI coupling-type optical multiplexing unit. Note that in Fig. 11, only the optical multiplexing unit, the optical input-side optical waveguide, and the optical output-side optical waveguide are shown, and other configurations are omitted.

[0065] FIG. 11A shows an example of an optical multiplexer in which the MMI type optical multiplexing section is a single-stage 3×1 MMI type optical multiplexing section. The optical multiplexing section 51, which is an MMI single type optical multiplexing section, has three optical input side optical waveguides 21-1, 21-2, and 21-3 connected to the optical input side, and one optical output side optical waveguide 22T connected to the optical output side. The lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section 51 and the optical output side optical waveguide 22T is larger than at least one of the two lower interior angles of the trapezoidal cross sections of the optical input side optical waveguides 21-1, 21-2, 21-3.

[0066] FIG. 11B shows an example of an optical multiplexer in which the MMI type optical multiplexing section is a single-stage 2×1 type MMI type optical multiplexing section. The optical multiplexing section 52, which is an MMI single-type optical multiplexing section, has two optical input side optical waveguides 121-1 and 121-2 connected to the optical input side, and one optical output side optical waveguide 122T connected to the optical output side. The lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section 52 and the optical output side optical waveguide 122T is larger than at least one of the two lower interior angles of the trapezoidal cross sections of the optical input side optical waveguides 121-1 and 121-2.

[0067] Like FIG. 11B, FIG. 11C shows an example of an optical multiplexer having a single-stage 2×1 MMI type optical multiplexing section, but the only difference is that the optical output side optical waveguide 122TT is arranged on an extension line of the optical input side optical waveguide 121-2, and the other points are the same. Therefore, the lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section 52 and the optical output side optical waveguide 122TT is larger than at least one of the two lower interior angles of the trapezoidal cross sections of the optical input side optical waveguides 121-1 and 121-2.

[0068] FIG. 11D shows an example of an MMI-coupling type optical multiplexing unit in which the optical multiplexer has two stages of MMI type optical multiplexing units. The two-stage MMI-coupled optical multiplexing section shown in FIG. 11D is an example in which two 2×1 type MMI single optical multiplexing sections 53-1 and 53-2 are coupled via an optical waveguide 223 (hereinafter sometimes referred to as a coupled optical waveguide 223). In the optical multiplexing unit 53, which is a two-stage MMI-coupled optical multiplexing unit, two optical input side optical waveguides 221-1 and 122-2 are connected to the optical input side of the front-stage MMI single-type optical multiplexing unit 53-1, and a coupled optical waveguide 223 is connected to the optical output side. In addition, the rear-stage MMI single-type optical multiplexing unit 53-2 has the coupled optical waveguide 223 and the optical input side optical waveguide 221-3 connected to the optical input side, and one optical output side optical waveguide 222T connected to the optical output side. The lower interior angle of the trapezoidal or rectangular cross section of the front-stage MMI single-type optical multiplexing unit 53-1 and the connecting optical waveguide 223 is larger than at least one of the two lower interior angles of the trapezoidal cross sections of the light input side optical waveguides 221-1 and 122-2. Also, the lower interior angle of the trapezoidal or rectangular cross section of the rear-stage MMI single-type optical multiplexing unit 53-2 and the light input side optical waveguide 221-3 is larger than at least one of the two lower interior angles of the trapezoidal cross sections of the connecting optical waveguide 223 and the light input side optical waveguide 221-3.

[0069] [Optical multiplexing member] The optical multiplexing member according to one embodiment includes a substrate made of a material different from lithium niobate and a lithium niobate film formed on a main surface of the substrate, and the optical multiplexer according to the above embodiment is formed on the lithium niobate film. Regarding the components described below, components having the same functions as those in the above embodiment will be assigned the same reference numerals, and their description may be omitted. The lithium niobate film included in the optical multiplexing member according to an embodiment may include any of the optical multiplexing portions shown in FIGS. 1, 6, and 11A to 11D.

[0070] Figure 12A is a schematic cross-sectional view of the optical multiplexer 100 shown in Figure 1 taken along the YZ plane (X-X' in Figure 1) of the optical multiplexing member 200 formed on a lithium niobate film, and Figure 12B is a schematic cross-sectional view of the optical multiplexer 110 shown in Figure 2 taken along the YZ plane (X-X' in Figure 2) of the optical multiplexing member 210 formed on a lithium niobate film.

[0071] The optical multiplexing member 200 shown in FIG. 12A includes a substrate 10 made of a material different from lithium niobate and a lithium niobate film 24 formed on the main surface of the substrate 10, and the optical multiplexer shown in FIG. 1 is formed in the lithium niobate film 24.

[0072] 13, the lithium niobate film 24 may be configured to include a ridge 24-1 protruding from the first surface 24A and a slab layer 24-2 other than the ridge. The ridge constitutes the optical input side optical waveguides 21-1, 21-2, and 21-3, the first MMI type optical multiplexing element 50-1, the second MMI type optical multiplexing element 50-2, and the optical output side optical waveguide 22T. The lithium niobate film 24 is covered with a buffer film 23. The lithium niobate film 24 and the buffer film 23 are collectively referred to as the optical multiplexing functional layer 20.

[0073] When the optical multiplexing member of this embodiment is used in an eyeglass-type image display device, the thickness (T slab ) is preferably 0.1 to 0.3 μm. When the optical multiplexing member of this embodiment is used in an eyeglass-type image display device, the thickness (T R The thickness (T R ) is small, light does not propagate, and if it is large, the propagating light becomes multimode. When the optical multiplexing member of this embodiment is used in an eyeglass-type image display device, the width (W R ) is preferably 0.3 to 1.2 μm. This is because if the waveguide width is small, light does not propagate, and if it is large, the propagating light becomes multimode. When the optical multiplexing member of this embodiment is used in an eyeglass-type image display device, the lower interior angle (α) of the ridge 24-1 having a trapezoidal cross section is 65° or more. This is because as the lower interior angle (inclination angle) becomes smaller, the propagating light becomes multimode. The lower interior angle of the trapezoidal or rectangular cross section of the first MMI optical multiplexing element and the optical output side optical waveguide is preferably 80° or more and 90° or less, and the lower interior angle of the trapezoidal cross section of the optical input side optical waveguide is preferably 65° or more and less than 80°.

[0074] Similar to FIG. 12A, the optical multiplexing member 210 shown in FIG. 12B includes a substrate 10 made of a material other than lithium niobate and a lithium niobate film 24 formed on the main surface of the substrate 10, and the optical multiplexer shown in FIG. 2 is formed in the lithium niobate film 24. 12A, the lithium niobate film 24 may be configured to include a ridge 24-1 protruding from the first surface 24A and a slab layer 24-2 other than the ridge. The ridge constitutes the optical input side optical waveguides 121-1 and 121-2, the first MMI type optical multiplexing element 150-1, the second MMI type optical multiplexing element 150-2, and the optical output side optical waveguide 122T. The lithium niobate film 24 is covered with a buffer film 23.

[0075] In the optical multiplexing member 200 and the optical multiplexing member 210, when the refractive index difference between the lithium niobate film and the buffer film is Δn, if the lithium niobate 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 optical multiplexing section, an increase in the coupling length can be prevented compared to when a directional coupler is used, thereby achieving both improved design freedom and miniaturization.

[0076] Examples of the substrate 10 include a sapphire substrate, a Si substrate, and a thermally oxidized silicon substrate. The substrate 10 is not particularly limited as long as it has a refractive index lower than that of a lithium niobate (LiNbO3) film, but a sapphire single crystal substrate or a silicon single crystal substrate is preferred as a substrate on which a 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 a c-plane substrate is preferred for a sapphire single crystal substrate, and a (111) plane substrate is preferred for a silicon single crystal substrate.

[0077] 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 a substrate 10. An epitaxial film is a single-crystal film whose crystal orientation is aligned by the underlying substrate. An epitaxial film is a film with 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 verified, for example, by checking the peak intensity and poles at the orientation position in 2θ-θ X-ray diffraction.

[0078] Specifically, when measured by 2θ-θ X-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 term for equivalent planes such as (001) and (002).

[0079] Furthermore, the conditions for confirming the peak intensity at the orientation position described above only indicate orientation in one direction. Therefore, even if the above conditions are met, if the crystal orientation is not uniform within the plane, the X-ray intensity will not increase at a specific angular position, and no pole points will be observed. For example, in the case of a lithium niobate film, because LiNbO3 has a trigonal crystal structure, there will be three pole points of LiNbO3 (014) in the single crystal. In the case of lithium niobate, it is known that epitaxial growth occurs in a so-called twin state, in which crystals rotated 180° around the c-axis are symmetrically bonded. In this case, three pole points are symmetrically bonded to two, resulting in six pole points. Furthermore, when a lithium niobate film is formed on a silicon single crystal substrate with a (100) plane, the substrate has four-fold symmetry, so 4 x 3 = 12 pole points are observed. Note that in this disclosure, lithium niobate films epitaxially grown in a twin state are also included in the term epitaxial film.

[0080] The composition of lithium niobate is Li x NbA y O z where 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. Examples of the element A include K, Na, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Cr, Mo, W, Fe, Co, Ni, Zn, Sc, and 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.

[0081] [Optical multiplexing component with optical modulation function] The optical multiplexing member with optical modulation function according to this embodiment includes a substrate made of a material different from lithium niobate and a lithium niobate film formed on the main surface of the substrate, and the lithium niobate film is integrated with the optical multiplexer according to the above embodiment and a Mach-Zehnder optical modulator connected to the optical multiplexer and guiding multiple visible light beams emitted from multiple visible light laser light sources to the optical multiplexer. Regarding the components described below, components having the same functions as those in the above embodiment will be assigned the same reference numerals, and their description may be omitted. The lithium niobate film included in the optical multiplexing member with optical modulation function according to this embodiment may include any of the optical multiplexing sections shown in FIGS. 1, 6, and 11A to 11D.

[0082] FIG. 14 is a schematic plan view of the optical multiplexing member with optical modulation function according to this embodiment. The optical multiplexing element 300 with optical modulation function shown in Figure 14 comprises a substrate 10 (see Figure 12A) made of a material other than lithium niobate, and a lithium niobate film 24 formed on the main surface of the substrate 10, and the optical multiplexing element 300 with optical modulation function is formed within the lithium niobate film 24.

[0083] The optical multiplexing member 300 with optical modulation function includes the 3×1 type optical multiplexing section 50 (see FIG. 1) according to the above embodiment, and a Mach-Zehnder type optical modulator 40. The Mach-Zehnder optical modulator 40 has three Mach-Zehnder optical waveguides 40-1, 40-2, and 40-3, but may have two or four or more depending on the number of input ports of the first MMI optical multiplexing element 50-1. The optical multiplexing element 300 with optical modulation function is configured to use a 3x1 type optical multiplexing section 50 as an optical multiplexer, but it can also be configured to use a 2x1 type optical multiplexing section 150 (see Figure 2) instead of the 3x1 type optical multiplexing section 50.

[0084] A known Mach-Zehnder optical modulator or an optical waveguide can be used as the Mach-Zehnder optical modulator 40. It splits (demultiplexes) an optical beam with a uniform wavelength and phase into two paired beams, gives each beam a different phase, and then combines them. The intensity of the combined optical beam changes depending on the phase difference.

[0085] Each of the Mach-Zehnder optical waveguides 40 (40-1, 40-2, 40-3) shown in FIG. 14 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 optical waveguide 40-1 is connected to the optical input side optical waveguide 21-1 of the first MMI optical multiplexing element 50-1. The output path 44 of the Mach-Zehnder optical waveguide 40-2 is connected to the optical input side optical waveguide 21-2 of the first MMI optical multiplexing element 50-1. The output path 44 of the Mach-Zehnder optical waveguide 40-3 is connected to the optical input side optical waveguide 21-3 of the first MMI optical multiplexing element 50-1. The first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 14 are configured to extend linearly in the x direction except near the branching portion 45 and the coupling portion 46, but are not limited to this configuration. The first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 14 have approximately the same length. The branching portion 45 is located 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 located 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.

[0086] The electrodes 25 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 25 is an example of a first electrode, and the electrode 26 is an example of a second electrode. One end of the electrode 25 is connected to a power supply 131, and the other end is connected to a termination resistor 132. One end of the electrode 26 is connected to the power supply 131, and the other end is connected to the termination resistor 132. The power supply 131 is a part of a drive circuit that applies a modulation voltage to each Mach-Zehnder optical waveguide 40. For simplicity of illustration, the electrodes 25 and 26 are only drawn in the area of ​​the Mach-Zehnder optical waveguide 40-3.

[0087] The electrodes 27 and 28 are electrodes that apply a DC bias voltage to each Mach-Zehnder optical waveguide 40. One end of the electrode 27 and one end of the electrode 28 are connected to a power supply 133. The power supply 133 is a part of a DC bias application circuit that applies a DC bias voltage to each Mach-Zehnder optical waveguide 40. When a DC bias voltage is superimposed on the electrodes 25 and 26, the electrodes 27 and 28 may not be provided. Also, ground electrodes may be provided around the electrodes 25, 26, 27, and 28.

[0088] Visible Light Source Module (First Embodiment) The visible light source module according to the first embodiment includes the optical multiplexer according to this embodiment and a plurality of visible light laser light sources that emit visible light that is multiplexed by the optical multiplexer. Fig. 15 is a plan view schematic diagram of a visible light source module according to the first embodiment. Fig. 15 shows an example of a visible light source module including the optical multiplexing member 200 (three-input type) shown in Fig. 12A. Fig. 16 is a plan view schematic diagram of a visible light source module including the optical multiplexing member 210 (two-input type) shown in Fig. 12B. The visible light source module according to the first embodiment may include any of the optical multiplexing sections shown in FIGS. 1, 6, and 11A to 11D.

[0089] 15 includes an optical multiplexer 200 having an MMI-coupled optical multiplexing section 50 in which a first MMI-type optical multiplexing element 50-1 and a second MMI-type optical multiplexing element 50-2 are connected, and three visible laser light sources 30 (30-1, 30-2, 30-3) that emit visible light multiplexed in the optical multiplexer 200. The optical multiplexer 200 includes a substrate 10 (see FIG. 12A) made of a material different from lithium niobate, and a lithium niobate film 24 (see FIG. 12A) formed on the main surface of the substrate 10, and has a side surface 200A. The optical multiplexer included in the visible light source module 1000 shown in FIG. 15 may be the optical multiplexer 100. Regarding the components shown in FIG. 15, components having the same functions as those described above are given the same reference numerals, and the description thereof may be omitted.

[0090] Various laser elements can be used as the visible light laser light source 30. For example, commercially available laser diodes (LDs) that emit red, green, blue, etc. can be used. For red light, light with a peak wavelength of 610 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 560 nm or less can be used, and for blue light, light with a peak wavelength of 435 nm or more and 480 nm or less can be used. In the visible light source module 1000, the visible light laser light sources 30-1, 30-2, and 30-3 are an LD that emits green light, an LD that emits blue light, and an LD that emits red light, respectively. The LDs 30-1, 30-2, and 30-3 are arranged 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 light source base 60 (see FIG. 16).

[0091] In the visible light source module 1000, two and three visible light laser light sources are exemplified, but the number is not limited to two or three, and may be four or more. The multiple visible light laser light sources may all emit light with different wavelengths, or some visible light laser light sources may emit light with the same wavelength. Furthermore, light other than red (R), green (G), and blue (B) can be used for the emitted light, and the mounting order of red (R), green (G), and blue (B) described using the drawings does not have to be this order and can be changed as appropriate.

[0092] Fig. 16 is a schematic cross-sectional view of a part of the light source module 1000 shown in Fig. 15 cut along the XZ plane, depicting only a part near the joint. The light source 7 is installed on the upper surface of a light source base 60. The light source base 60 may be common to all the light sources or may be individual for each light source. The light source base 60 is made of, for example, aluminum nitride (AlN), aluminum oxide (Al2O3), silicon (Si), or the like.

[0093] The light source base 60 and the optical waveguide substrate 10 on which the optical multiplexing function layer 20 is formed can be directly bonded via a metal layer 70. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. By configuring the bonding surface 60A of the light source base 60 and the bonding surface 10A of the optical waveguide substrate 10 to be bonded via the metal layer 70, the relative positions of the light source base 60 and the optical waveguide substrate 10 can be adjusted during manufacturing, and the optical axis position of the laser light can be aligned so that the optical axis of each light source 30 coincides with the axis of the input waveguide (active alignment).

[0094] Metal layer 70 may consist of multiple metal layers.

[0095] When the light source module of this embodiment is used in XR glasses, taking into consideration the amount of light required in the XR glasses, etc., it is preferable that the gap (spacing) S between the bonding surface 60A of the light source base 60 and the bonding surface 10A of the optical waveguide substrate 10 be, for example, greater than 0 μm and not greater than 5 μm.

[0096] (Drive method) An optical modulator can modulate input light into output light using a high-frequency modulation voltage and a DC bias voltage. The operating point Vd of the optical modulator is adjusted by controlling the DC bias voltage Vdc. The operating point Vd is the voltage at the center of the modulation voltage amplitude Vpp. The half-wave voltage of the high-frequency modulation voltage is defined as Vπ(RF).

[0097] 17A to 17C are diagrams for explaining three examples of a method for driving an optical modulator. 17A to 17C, the horizontal axis represents the DC bias voltage applied to the optical modulator, and the vertical axis represents the intensity of the optical output at the applied voltage. The applied voltage width Vpp is the difference between the minimum value (Vmin) and the maximum value (Vmax) of the applied voltage.

[0098] 17A shows an example in which the DC bias voltage can be set to approximately 0 V by setting the operating point Vd' so that the shift amount of the operating point voltage is (Vn-0.5Vπ). For example, if the applied voltage width Vpp of the modulation voltage Vm is the half-wave voltage Vπ(RF), then a modulation voltage Vm in the range of (-1 / 2)Vπ(RF) to (1 / 2)Vπ(RF) is applied to the optical modulator. As shown in FIG. 17A, the optical output from the optical modulator is maximum when the modulation voltage Vm is (-1 / 2)Vπ(RF), minimum when the modulation voltage Vm is (1 / 2)Vπ(RF), and the optical output when the modulation voltage Vm is 0 V is 50% of the maximum output.

[0099] Similarly, using Figure 17B, we will explain the optical modulation of an optical modulator in which the operating point Vd' is set so that the shift amount of the operating point voltage is (Vn-0.25Vπ) and the applied voltage width Vpp of the modulation voltage Vm is controlled as a (1 / 4) wavelength voltage (1 / 2)Vπ(RF). In this case, if the operating point voltage shift is set to (Vn-0.25Vπ), the operating point Vd' can be set to a DC bias voltage of approximately 0 (V). A modulation voltage Vm corresponding to the range from (-1 / 4)Vπ(RF) to (1 / 4)Vπ(RF) is applied to the optical modulator. As shown in Figure 17B, the optical output from the optical modulator is maximum when the modulation voltage Vm is (-1 / 4)Vπ(RF) and minimum when the modulation voltage Vm is (1 / 4)Vπ(RF). When the modulation voltage Vm is 0V(Vd'), the optical output is 15% of the maximum output.

[0100] Similarly, using Figure 17C, we will explain the optical modulation of an optical modulator in which the operating point Vd' is set so that the shift amount of the operating point voltage is (Vn-0.75Vπ) and the applied voltage width Vpp of the modulation voltage Vm is controlled as a (1 / 4) wavelength voltage (1 / 2)Vπ(RF). In this case, if the operating point voltage shift is set to (Vn-0.75Vπ), the operating point Vd' can be set to a DC bias voltage of approximately 0 (V). A modulation voltage Vm corresponding to the range from (-1 / 4)Vπ(RF) to (1 / 4)Vπ(RF) is applied to the optical modulator. As shown in Figure 17C, the optical output from the optical modulator is maximum when the modulation voltage Vm is (-1 / 4)Vπ(RF) and minimum when the modulation voltage Vm is (1 / 4)Vπ(RF). When the modulation voltage Vm is 0V(Vd'), the optical output is 85% of the maximum output.

[0101] [Visible Light Source Module (Second Embodiment)] FIG. 18 is a schematic plan view of the visible light source module according to the second embodiment. 18 includes the optical multiplexing member with optical modulation function 300 shown in Fig. 14, and a plurality of visible laser light sources 30 (30-1, 30-2, 30-3) that emit visible light that is multiplexed in the optical multiplexing member with optical modulation function 300. The optical multiplexing member 300 includes a substrate 10 (see Fig. 12A) made of a material different from lithium niobate, and a lithium niobate film 24 (see Fig. 12A) formed on the main surface of the substrate 10, and has a side surface 300A. Regarding the components shown in FIG. 18, components having the same functions as those described above are given the same reference numerals, and the description thereof may be omitted. Although the visible light source module 2000 is configured to use a 3x1 type optical multiplexing section 50 as an optical multiplexer, it can be configured to use a 2x1 type optical multiplexing section 150 (see Figure 6) instead of the 3x1 type optical multiplexing section 50. The visible light source module according to the second embodiment may include any of the optical multiplexing sections shown in FIGS. 1, 6, and 11A to 11D.

[0102] The visible light source module 2000 has three Mach-Zehnder optical waveguides 40-1, 40-2, 40-3, the same number as the visible light laser light sources 30-1, 30-2, 30-3. The visible light laser light sources 30-1, 30-2, 30-3 and the Mach-Zehnder optical waveguides 40-1, 40-2, 40-3 are positioned so that light emitted from the visible light laser light sources enters the corresponding Mach-Zehnder optical waveguide.

[0103] The light source base 60 on which the visible light laser light sources 30-1, 30-2, and 30-3 are mounted can be directly bonded via a metal bonding layer to the substrate 10 on which the optical multiplexing function layer 20 having the optical multiplexing member 300 with optical modulation function is formed. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. Furthermore, during manufacturing, the relative positions of the light source base 60 and the substrate 10 can be adjusted to align the optical axis position of the laser light so that the optical axis of each visible light laser coincides with the axis of the input path 43 of each of the Mach-Zehnder optical waveguides 40-1, 40-2, and 40-3 (active alignment).

[0104] The size of the optical multiplexing functional layer 20 is, for example, 100 mm 2 The size of the optical multiplexing functional layer 20 is 100 mm or less. 2 If it meets the following criteria, it is suitable for use with XR glasses such as AR glasses and VR glasses.

[0105] The optical multiplexing functional layer 20 can be fabricated by a known method, for example, by using semiconductor processes such as epitaxial growth, photolithography, etching, vapor phase growth, and metallization.

[0106] 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 MMI type optical multiplexing element and the second MMI type optical multiplexing element constituting the optical multiplexer is preferably, for example, about 5 to 15 μm, and the length thereof is preferably, for example, about 100 to 1000 μm.

[0107] For example, in a retinal projection display, to display an image in the desired color, it is necessary to independently and quickly modulate the intensity of each of the three colors (RGB) that represent visible light. Performing such modulation solely with a visible laser light source (current modulation) places a heavy load on the IC controlling the modulation. However, it is possible to also use modulation (voltage modulation) with a Mach-Zehnder optical modulator 40 (optical combining component 300 with optical modulation function). In this case, coarse adjustment can be performed with current (visible laser light source) and fine adjustment with voltage (Mach-Zehnder optical modulator 40). Alternatively, coarse adjustment can be performed with voltage (Mach-Zehnder optical modulator 40) and fine adjustment with current (visible laser light source). Since fine adjustment with voltage provides better responsiveness, the former is preferred when responsiveness is important. However, fine adjustment with current requires less current and therefore reduces power consumption, so the latter is preferred when power consumption reduction is important.

[0108] [Optical engine and XR glasses] In this specification, an optical engine is a device that includes a plurality of light sources, an optical system including a multiplexing unit that combines the plurality of light beams emitted from the plurality of 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.

[0109] Fig. 19 is a conceptual diagram for explaining an example of the XR glasses of the present invention. Fig. 20 is a conceptual diagram showing how an image is projected directly onto the retina by laser light emitted from the light source module in the XR glasses shown in Fig. 19. Symbol L is image display light.

[0110] The XR glasses (eyeglasses) 10000 of this embodiment are glasses-type terminals. XR is a general term for virtual reality (VR), augmented reality (AR), and mixed reality. The symbol L shown in FIG. 20 denotes image display light.

[0111] The XR glasses 10000 of this embodiment shown in FIG. 19 are configured such that the light source module 1000 according to the above-described embodiment is mounted on an optical engine 5001 installed in a frame 1010. As shown in FIG. 19, the optical engine 5001 includes a light source module 1000, an optical scanning mirror 3001, an optical system 2001 connecting the light source module 1000 and the optical scanning mirror 3001, a laser driver 1100, an optical scanning mirror driver 1200, and a video controller 1300 that controls these drivers.

[0112] For example, a MEMS mirror can be used as the optical scanning mirror 3001. In order to project a 2D image, it is preferable to use, as the optical scanning mirror 3001, a two-axis MEMS mirror that vibrates so as to reflect laser light while changing the angle in the horizontal direction (X direction) and the vertical direction (Y direction).

[0113] The optical system 2001 optically processes the laser light emitted from the light source module 1000. The optical system 2001 may include, for example, a collimator lens 2001a, a slit 2001b, and an ND filter 2001c. The optical system 2001 shown in Fig. 19 is an example, and other configurations may also be used.

[0114] In the XR glasses 10000 of this embodiment shown in Figure 19, as shown in Figure 20, laser light R emitted from the light source module 1000 attached to the frame 1010 is reflected by the optical scanning mirror 3001, and further reflected by the lens 4001 of the XR glasses 10000, enters the human eyeball E as image display light L, and an image (video) can be projected directly onto the retina M.

[0115] The XR glasses 10000 of this embodiment are equipped with the light source module 1000 of this embodiment, and therefore have reduced electric field efficiency.

[0116] The above describes the embodiments of the present invention in detail with reference to the drawings. However, each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications of the configurations are possible within the scope that does not deviate from the spirit of the present invention. [Example]

[0117] The present invention will be described in more detail below using examples, but the present invention is not limited to the examples shown below.

[0118] <3-input, 1-output MMI-coupled optical multiplexer> The coupling loss of the three RGB colors of light (loss of light intensity at output after the input light intensity passes through the MMI coupled optical combiner) of a model of an MMI coupled optical combiner in which a wide input-side MMI optical combiner and a narrow output-side MMI optical combiner are coupled as shown in Figure 1 was compared by simulation with that of a conventional MMI coupled optical combiner model. The simulation software used was Fimmwave (Photon Design).

[0119] Example 1 The parameters of the model of the MMI coupling type optical multiplexer according to the first embodiment were set as follows (see FIG. 21). (width and length) Width of the optical waveguide on the optical input side W in :2μm (common to RGB) Width of the MMI type optical multiplexer on the input side W1: 13 μm Width of the output MMI type optical multiplexer W2: 7 μm Length of the MMI type optical multiplexer on the input side L1: 328 μm Length of the output MMI type optical multiplexer L2: 690 μm Width of the optical waveguide on the optical output side W out :2μm The width W of the optical waveguide (ridge) on the optical input side in and the width W of the optical waveguide (ridge) on the optical output side outEach of these is the width of the part that connects to the MMI type optical multiplexer, and a model is adopted in which the width increases continuously in plan view from the Z direction from a predetermined position of the optical waveguide to the part that connects to the MMI type optical multiplexer, and the model has a tapered shape that allows the inclination angle to be defined. The length of the tapered part is 50 μm, and it gradually widens from a width of 0.8 μm, and the width of the part that connects to the MMI type optical multiplexer is 2 μm (W in , W out ) In FIG. 21, the shape of the tapered portion is not shown. (lower interior angle) Two lower internal angles of the optical input waveguide: 70° (common to RG) The two lower internal angles of the optical input waveguide: 76° (B) The two lower inner angles of the MMI type optical multiplexer on the input side: 83° The two lower inner angles of the output MMI type optical multiplexer: 83° Two lower inner angles of the optical output waveguide: 88° (common to RGB) (wavelength of optical waveguide on the optical input side) Wavelength of the optical input side optical waveguide 21-1: 637 μm (red R) Wavelength of the optical input side optical waveguide 21-2: 455 μm (blue B) Wavelength of the optical input side optical waveguide 21-3: 520 μm (green G) (distance between adjacent optical input waveguides) Distance d1 between the top surfaces of adjacent optical input waveguides: 1.5 μm Distance d2 between the top surfaces of adjacent optical input waveguides: 1.5 μm As shown in the figure, the distances d1 and d2 between the upper surfaces are the distances between the upper surfaces of the portions of the adjacent optical input side optical waveguides that are connected to the MMI type optical multiplexing portion.

[0120] Comparative Example 1 The parameters of the model of the MMI coupling type optical multiplexer according to Comparative Example 1 were as follows: The model was the same as that of Example 1, except that the lower interior angle was set as follows: (lower interior angle) Two lower internal angles of the optical input waveguide: 70° (common to RG) The two lower internal angles of the optical input waveguide: 76° (B) The two lower internal angles of the MMI type optical multiplexer on the input side: 88° The two lower inner angles of the output MMI type optical multiplexer: 88° Two lower inner angles of the optical output waveguide: 88° (common to RGB)

[0121] The coupling losses of Example 1 were 4.7 dB, 4.5 dB, and 3.9 dB for R, G, and B, respectively. The coupling losses of Comparative Example 1 were 5.6 dB, 5.4 dB, and 4.1 dB for R, G, and B, respectively. As described above, the coupling loss in Example 1 was smaller than the coupling loss in Comparative Example 1 for light of any of the RGB wavelengths.

[0122] <2-input, 1-output MMI single-type optical multiplexer> The coupling loss of the R, B, and C colors of the MMI-only optical multiplexer model shown in Figure 11C (loss of optical intensity at output after passing through the MMI-only optical multiplexer from the input) was compared with that of a conventional MMI-only optical multiplexer model by simulation. Fimmwave (Photon Design) was used as the simulation software.

[0123] Example 2 The parameters of the model of the MMI single-type optical multiplexing unit according to the second embodiment were set as follows (see FIG. 22). (width and length) Width of the optical waveguide on the optical input side W in : 1.6 μm (common to RB) MMI single type optical multiplexer width W1: 6μm MMI single type optical multiplexer length L1: 515 μm Width of the optical waveguide on the optical output side W out :2μm The width W of the optical waveguide (ridge) on the optical input side in and the width W of the optical waveguide (ridge) on the optical output side outEach of these is the width of the part that connects to the MMI type optical multiplexer. When viewed from above in the Z direction, the width increases continuously from a predetermined position on the optical waveguide to the part that connects to the MMI type optical multiplexer, and a model with a tapered shape that allows the inclination angle to be defined is used. The length of the tapered part is 50 μm, and it gradually widens from a width of 0.8 μm, until the width of the part that connects to the MMI type optical multiplexer is 1.6 μm (W in ), 2 μm (2 μm). In FIG. 22, the shape of the tapered portion is not shown. (lower interior angle) Two lower internal angles of the optical input waveguide: 70° (common to RB) Two lower interior angles of the MMI single-type optical multiplexer: 83° Two lower internal angles of the optical output waveguide: 88° (common to RB) (wavelength of optical waveguide on the optical input side) Wavelength of the optical input side optical waveguide 21-1: 637 μm (red R) Wavelength of the optical input side optical waveguide 21-2: 455 μm (blue B) (distance between adjacent optical input waveguides) Distance d1 between the top surfaces of adjacent optical input waveguides: 1.4 μm As shown in the figure, the distance d1 between the upper surfaces is the distance between the upper surfaces of the portions of the adjacent optical input side optical waveguides that are connected to the MMI type optical multiplexing portions.

[0124] Comparative Example 2 The parameters of the model of the MMI single-type optical multiplexing unit according to Comparative Example 2 were as follows: The model was the same as that of Example 1, except that the lower interior angle was set as follows: (lower interior angle) Two lower internal angles of the optical input waveguide: 88° (common to RB) The two lower interior angles of the MMI single-type optical multiplexer: 88° Two lower internal angles of the optical output waveguide: 88° (common to RB)

[0125] The coupling losses of Example 2 were 2 dB and 2.8 dB for R and B, respectively. The coupling losses of Comparative Example 2 were 3.1 dB and 3 dB for R and B, respectively. As described above, the coupling loss in Example 2 was smaller than the coupling loss in Comparative Example 2 for all wavelengths of RB light. [Explanation of symbols]

[0126] 10 Substrate 20 Optical multiplexing functional layer 24 Lithium niobate film 30, 130 Visible light laser light source 40 Mach-Zehnder optical modulator 50, 150 MMI type optical multiplexer (MMI type optical multiplexer) 50-1, 150-1 First MMI type optical multiplexing element 50-2, 150-2 Second MMI type optical multiplexing element 51, 52 MMI single type optical multiplexer (MMI type optical multiplexer) 53 MMI connected type optical multiplexer (MMI type optical multiplexer) 100, 110 optical multiplexer 200, 210 Optical multiplexing member 300 Optical multiplexer with optical modulation function 1000, 2000 Visible Light Source Module 10000 XR Glasses

Claims

1. An optical multiplexer that multiplexes laser beams of different wavelengths, an optical multiplexing unit; a plurality of optical input side optical waveguides connected to the optical multiplexing unit; one optical output side optical waveguide connected to the optical multiplexing unit, the optical multiplexing unit is composed of a single-stage or multi-stage MMI type optical multiplexing unit, the optical input side optical waveguide has a trapezoidal cross section; the optical multiplexing section and the optical output side optical waveguide have trapezoidal or rectangular cross sections, an optical multiplexer in which a lower interior angle of the trapezoidal or rectangular cross section of the optical multiplexing section and the optical output side optical waveguide is larger than at least one of two lower interior angles of the trapezoidal cross section of the optical input side optical waveguide.

2. 2. The optical multiplexer according to claim 1, wherein the lower interior angles of the trapezoidal or rectangular cross sections of the optical multiplexing section and the optical output side optical waveguide are 80° or more and 90° or less, and the lower interior angle of the trapezoidal cross section of the optical input side optical waveguide is 65° or more and less than 80°.

3. 2. The optical multiplexer according to claim 1, wherein each of said one-stage or multiple-stage MMI type optical multiplexing sections is a 3.times.1 type MMI type optical multiplexing section or a 2.times.1 type MMI type optical multiplexing section.

4. At least one of the one-stage or multiple-stage MMI type optical multiplexing units is an MMI-coupled optical multiplexing unit in which a first MMI type optical multiplexing element and a second MMI type optical multiplexing element are coupled from the input side, 2. The optical multiplexer according to claim 1, wherein the width of said first MMI type optical multiplexing element is wider than the width of said second MMI type optical multiplexing element.

5. 2. The optical multiplexer according to claim 1, wherein the plurality of different wavelengths are all visible light wavelengths.

6. a substrate made of a material different from lithium niobate; a lithium niobate film formed on a main surface of the substrate, 6. An optical multiplexing member, wherein the optical multiplexer according to claim 1 is formed on the lithium niobate film.

7. A visible light source module comprising: the optical multiplexing member according to claim 6; and a plurality of visible laser light sources that emit visible light that is multiplexed by the optical multiplexing member.

8. 7. An optical multiplexing member with an optical modulation function, comprising: the optical multiplexing member according to claim 6; and a Mach-Zehnder optical modulator connected to the optical multiplexing member, which guides a plurality of visible light beams emitted from a plurality of visible light laser light sources to the optical multiplexer.

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

10. The visible light source module according to claim 7 ; an optical scanning mirror that reflects the light emitted from the visible light source module at different angles so as to display an image;

11. The visible light source module according to claim 9 ; an optical scanning mirror that reflects the light emitted from the visible light source module at different angles so as to display an image;

12. XR glasses equipped with the optical engine according to claim 10.

13. XR glasses equipped with the optical engine according to claim 11.

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