Electro-optical element, light source module, optical engine, and xr glasses

Abstract

To provide an electro-optical element in which degradation in efficiency of an output light intensity with respect to an input light intensity while input light is monitored.SOLUTION: An electro-optical element 100 includes a substrate and an optical function layer. The optical function layer has: a light input port 21-1i; an optical branch portion 50-1 in which a light incident side waveguide 21-1 guiding visible light input through the light input port 21-1i is connected to one optical waveguide 41-m for monitoring and two optical modulation optical waveguides 41-1 and 41-2; a Mach-Zehnder optical modulation portion 40 that modulates visible light guided by the two optical modulation optical waveguides 41-1 and 41-2; a 2×1 type optical coupling portion 50-2 that couples two beams of visible light modulated by the Mach-Zehnder optical modulation portion 40; a light output side waveguide 22-1 that guides light coupled by the optical coupling portion 50-2 to a light output port 22-1o; the light output port 22-1o; and a monitoring light output port 41-mo.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electro-optical element, a light source module, an optical engine, and XR glasses. [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] Patent Document 1 discloses a signal generating section of an image display device that includes a light detecting section that detects the amount of the remaining light that is not incident on the optical fiber out of the light emitted from a light source to an optical fiber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6728596 Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration disclosed in Patent Document 1 requires an optical fiber between the light source and the optical modulator.

[0006] In PLC (Planar Lightwave Circuit) equipped with a light source such as LD (Laser Diode), the temperature dependency of the light source becomes an issue. Fluctuations in the light intensity of the emitted light occur due to fluctuations in the light intensity of the LD caused by temperature fluctuations in the LD. For this reason, it is necessary to branch the monitor light from the main waveguide, feed back the fluctuations in the light intensity of the monitor light to the control unit, and control the current given to the LD.

[0007] In addition, LN modulators used in communications have problems with DC drift and temperature drift, and from the viewpoint of long-term reliability, it is necessary to monitor the operating point fluctuation and provide feedback to the DC control unit. For this reason, it is necessary to split the light after passing through the interaction section in the Mach-Zehnder type optical modulator, where electrodes are formed to apply an electric field to the waveguide, into two and monitor the modulated light. For this reason, for example, a 2x2 multimode interferometer (MMI) is used to split the modulated light into two, and separate it into monitor light and output light. In this case, there is an issue that the output light is at most half the input light.

[0008] Since XR glass is used for a short period of time, the effects of DC drift and temperature drift of LN (lithium niobate (LiNbO3)) are small enough that they do not need to be taken into consideration. Therefore, it is sufficient to monitor only the temperature dependence of the LD. The inventor came up with a configuration in which the input light is split into three, two of which are provided with electrodes to form a Mach-Zehnder type optical modulator, and the remaining branch is output as monitor light. With this configuration, it is possible to make the output light a maximum of 2 / 3 of the input light.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an electro-optical element, a light source module, an optical engine, and XR glasses that are capable of suppressing a decrease in the efficiency of output light intensity relative to input light intensity while monitoring input light. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following means.

[0011] A first aspect of the present invention is an electro-optical element comprising a substrate and an optical functional layer formed on a main surface of the substrate, the optical functional layer having an optical input port capable of inputting visible light emitted from a visible light laser light source, a light incident side waveguide that guides the visible light input from the optical input port, an optical branching section in which one monitor optical waveguide and multiple optical modulation optical waveguides are connected, a Mach-Zehnder type optical modulation section that modulates the visible light guided through the multiple optical modulation optical waveguides, an optical combining section that combines two visible lights modulated by the Mach-Zehnder type optical modulation section, an optical output side waveguide that guides the light combined in the optical combining section to an optical output port, an optical output port through which light guided through the optical output side waveguide is output to the outside, and a monitor optical output port through which light guided through the monitor optical waveguide is output to a photodetector.

[0012] A second aspect of the present invention is the electro-optical element of the first aspect, wherein the plurality of optical waveguides for optical modulation are two optical waveguides for optical modulation.

[0013] A third aspect of the present invention is an electro-optical element according to the first or second aspect, wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

[0014] A fourth aspect of the present invention is the electro-optical element according to any one of the first to third aspects, wherein the optical branching section and the optical multiplexing section each constitute a multimode interferometer.

[0015] A fifth aspect of the present invention relates to an electro-optical element according to any one of the first to fourth aspects, the electro-optical element including three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, and three optical output ports that output the three visible light beams with different wavelengths to the outside.

[0016] A sixth aspect of the present invention relates to an electro-optical element according to any one of the first to fourth aspects, the electro-optical element including three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, an optical multiplexing section that multiplexes the three visible light beams with different wavelengths, and one optical output port that outputs the light multiplexed by the optical multiplexing section to the outside.

[0017] A seventh aspect of the present invention is an electro-optical element according to the first aspect, wherein the plurality of optical waveguides for optical modulation are (N1-1) (N1 is an integer equal to or greater than 3) optical waveguides for optical modulation, and an (N1-1)×2 type optical multiplexing and branching section is provided between the optical branching section and the Mach-Zehnder type optical modulation section, in which the (N1-1) optical waveguides for optical modulation are connected to the input side and two optical waveguides connected to the Mach-Zehnder type optical modulation section are connected to the output side.

[0018] An eighth aspect of the present invention is the electro-optical element of the seventh aspect, wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

[0019] A ninth aspect of the present invention is an electro-optical element according to the seventh or eighth aspect, wherein the optical branching section and the optical multiplexing section each constitute a multimode interferometer. The (N1-1)×2 type optical multiplexing / branching section may also constitute a multimode interferometer.

[0020] A tenth aspect of the present invention relates to an electro-optical element according to any one of aspects seven to ninth, comprising three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, respectively, and three optical output ports that output the three visible light beams with different wavelengths to the outside.

[0021] An eleventh aspect of the present invention relates to an electro-optical element according to any one of aspects seven to ninth, comprising three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, an optical multiplexing section that multiplexes the three visible light beams with different wavelengths, and one optical output port that outputs the light multiplexed by the optical multiplexing section to the outside.

[0022] A twelfth aspect of the present invention is an electro-optical element according to the first aspect, wherein the plurality of optical waveguides for optical modulation are 2N2 (N2 is an integer equal to or greater than 2) optical waveguides for optical modulation, and two N2×1 type optical branching sections are provided between the optical branching section and the Mach-Zehnder type optical modulation section, and each of the two N2×1 type optical branching sections has N2 of the 2N2 optical waveguides for optical modulation connected to it on the incident side, and has one optical waveguide connected to the Mach-Zehnder type optical modulation section connected to it on the exit side.

[0023] A thirteenth aspect of the present invention is the electro-optical element of the twelfth aspect, wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

[0024] A fourteenth aspect of the present invention is the electro-optical element of the twelfth or thirteenth aspect, wherein the two N2×1 type optical branching units constitute a multimode interferometer. The optical branching unit and the optical multiplexing unit may also constitute a multimode interferometer.

[0025] A fifteenth aspect of the present invention relates to an electro-optical element according to any one of aspects 12 to 14, comprising three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, respectively, and three optical output ports that output the three visible light beams with different wavelengths to the outside.

[0026] A sixteenth aspect of the present invention relates to an electro-optical element according to any one of aspects 12 to 14, comprising three optical input ports capable of inputting three visible light beams with different wavelengths output from three visible light laser light sources, an optical multiplexing section that multiplexes the three visible light beams with different wavelengths, and one optical output port that outputs the light multiplexed by the optical multiplexing section to the outside.

[0027] A seventeenth aspect of the present invention is a light source module comprising an electro-optical element according to any one of aspects 1 to 16, a visible light laser light source that outputs visible light input from the optical input port, and a laser light intensity control unit that detects monitor light from the monitor light output port with a photodetector and adjusts the intensity of the laser light emitted from the visible light laser light source in accordance with the detected light intensity.

[0028] An eighteenth embodiment of the present invention is an optical engine having the light source module of the seventeenth embodiment mounted thereon.

[0029] A nineteenth aspect of the present invention is an XR glass equipped with the light source module of the seventeenth aspect. Effect of the Invention

[0030] According to the present invention, it is possible to provide an electro-optical element capable of suppressing a decrease in efficiency of output light intensity relative to input light intensity while monitoring input light. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a plan view illustrating an electro-optical element according to a first embodiment. [Diagram 2] 2 is a schematic cross-sectional view of the electro-optical element shown in FIG. 1 taken along the line XX'. [Diagram 3] FIG. 11 is a plan view illustrating an electro-optical element according to a second embodiment. [Figure 4] FIG. 11 is a plan view illustrating an electro-optical element according to a third embodiment. [Figure 5A] 5 is a schematic plan view showing a modified example of the electro-optical element according to the first embodiment. FIG. [Figure 5B] 5 is a schematic plan view showing another modified example of the electro-optical element according to the first embodiment. FIG. [Figure 6] FIG. 13 is a schematic plan view showing a light source module according to a fourth embodiment. [Figure 7] FIG. 13 is a schematic plan view showing a light source module according to a fifth embodiment. [Figure 8]FIG. 13 is a schematic plan view showing a light source module according to a sixth embodiment. [Figure 9A] FIG. 13 is a schematic plan view showing a modified example of the light source module according to the fourth embodiment. [Figure 9B] FIG. 13 is a schematic plan view showing another modified example of the light source module according to the fourth embodiment. [Figure 10] 1 is a conceptual diagram for explaining an optical engine and XR glasses according to an embodiment of the present invention. FIG. [Figure 11] 1 is a conceptual diagram showing how an image is directly projected onto a retina by laser light emitted from a light source module according to the present embodiment. FIG. [Figure 12A] 1 is a plan view of a model of an optical branching section and an optical waveguide connected thereto, which were used in the simulation of Experimental Example 1. FIG. [Figure 12B] FIG. 12B is a schematic cross-sectional view taken along line AA in FIG. 12A. [Figure 12C] FIG. 12B is a schematic cross-sectional view taken along line BB in FIG. 12A. [Figure 13A] FIG. 13 is a plan view of a model of an optical branching unit and an optical waveguide connected thereto, which were used in the simulation of Experimental Example 2. [Figure 13B] FIG. 13B is a schematic cross-sectional view taken along line AA in FIG. 13A. [Figure 13C] FIG. 13B is a schematic cross-sectional view of line BB in FIG. 13A. [Figure 14A] 13 is a plan view of a model of an optical branching unit and an optical waveguide connected thereto, which were used in the simulation of Experimental Example 3. FIG. [Figure 14B] FIG. 14B is a schematic cross-sectional view taken along line AA in FIG. 14A. [Figure 14C] FIG. 14B is a schematic cross-sectional view of line BB in FIG. 14A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] 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.

[0033] [Electro-optical element] Fig. 1 is a schematic plan view showing an electro-optical element according to a first embodiment of the present invention, Fig. 2 is a schematic cross-sectional view of the electro-optical element shown in Fig. 1 taken along line XX'.

[0034] The electro-optical element 100 shown in FIG. 1 includes a substrate 10 and an optical functional layer 20 formed on a main surface 10a of the substrate 10. The optical functional layer 20 includes an optical input port 21-1i to which visible light emitted from a visible light laser light source can be input, a light incident side waveguide 21-1 that guides the visible light input from the optical input port 21-1i, an optical branching section 50-1 to which one monitor optical waveguide 41-m and two optical modulation optical waveguides 41-1 and 41-2 are connected, and a light branching section 50-2 to which the visible light guided through the two optical modulation optical waveguides 41-1 and 41-2 is connected. the optical output port 22-1o through which the light guided through the optical output waveguide 22-1 is output to the outside; and a monitor optical output port 41-mo through which the light guided through the monitor optical waveguide 41-m is output to the photodetector.

[0035] In the electro-optical element 100 shown in Fig. 1, the laser light input from the visible light laser light source to the optical input port 21-1i is branched into three optical waveguides by a 1-input 3-output (1x3) optical branching section 50-1, and the light guided in one of the optical waveguides is used as monitor light. In this configuration, only 1 / 3 of the intensity (Pin) of the laser light input to the optical input port 21-1i is used for monitoring (Pmonitor=1 / 3Pin), and the remaining 2 / 3 can be used for optical output (Pout=2 / 3Pin). In other words, 2 / 3 of the intensity of the input light can be used for output light, and the efficiency of the output light relative to the input light is improved to 2 / 3.

[0036] 1 has four side surfaces 100A, 100B, 100C, and 100D, and the optical input port 21-1i is provided on the first side surface 100A, the optical output port 22-1o is provided on the third side surface 100C, and the monitor optical output port 41-mo is provided on the second side surface 100B, but is not limited thereto. The optical input port 21-1i, the optical output port 22-1o, and the monitor optical output port 41-mo may be provided on the upper surface of the electro-optical element 100 using structures such as grating couplers and mirrors. In this case, the optical input port 21-1i, the optical output port 122-1o, and the monitor optical output port 141-mo do not need to be provided on the four side surfaces 100A, 100B, 100C, and 100D, and may be provided anywhere on the upper surface of the electro-optical element 100.

[0037] The optical branching unit 50-1 and the optical multiplexing unit 50-2 can be any known optical branching unit and optical multiplexing unit, but both can be multimode interferometers (MMIs). By using a multimode interferometer, it is possible to reduce efficiency degradation due to manufacturing variations.

[0038] In the electro-optical element 100 shown in FIG. 1, there are two optical waveguides for optical modulation through which the light branched by the optical branching section 50-1 is guided; however, two is just an example and the number of optical waveguides is not limited to two, and there may be three or more optical waveguides.

[0039] The Mach-Zehnder type optical modulation section 40 can have a known configuration. The electrodes 26 and 27 are electrodes that apply a modulation voltage to the Mach-Zehnder type optical modulator 40. One end of the electrode 26 is connected to a power supply 131, and the other end is connected to a termination resistor 132. One end of the electrode 27 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 the Mach-Zehnder type optical modulator 40.

[0040] In the electro-optical element 100 shown in FIG. 1, the substrate 10 may be made of a material other than lithium niobate, and the optical function layer 20 may be made of lithium niobate. By using a lithium niobate film as the optical function layer 20 through which visible light propagates, it is possible to reduce the loss of visible light propagation.

[0041] In electro-optical element 100, 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 multi-mode interference type optical combining 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.

[0042] The optical functional layer 20 includes an optical input port 21-1i, an optical incident side waveguide 21-1, one monitor optical waveguide 41-m, two optical modulation optical waveguides 41-1 and 41-2, an optical branching section 50-1, a Mach-Zehnder type optical modulation section 40, an optical multiplexing section 50-2, an optical output side waveguide 22-1, an optical output port 22-1o, a waveguide core film 24 including a monitor optical output port 41-mo, and a waveguide clad (buffer) film 25 formed on the waveguide core film 24 so as to cover these. Hereinafter, the symbol 24 may be used to refer to the lithium niobate film.

[0043] Examples of the substrate 10 include a sapphire substrate, a Si substrate, and a thermally oxidized silicon substrate. Since the optical 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 since, for example, 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.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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. The cross-sectional shapes of the cross-sectional shape fixed portions of the monitor optical waveguide 41-m and the two optical modulation optical waveguides 41-1 and 41-2 are rectangular, but may be any shape that can guide light, such as trapezoid, triangle, semicircle, etc. The width Wa of the three ridges in the y direction is preferably 0.2 μm or more and 5.0 μm or less, and the height of the three ridges (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 the other optical waveguides.

[0050] By making the cross-sectional dimension of the optical waveguide approximately the wavelength of the laser light, it is possible to achieve single-mode propagation.

[0051] 3 is a plan view schematic diagram showing an electro-optical element according to the second embodiment. In the following, illustrations and descriptions of parts common to the electro-optical element according to the first embodiment may be omitted.

[0052] The electro-optical element 101 shown in FIG. 3 includes a substrate 10 (see FIG. 2) and an optical functional layer 20 (see FIG. 2) formed on a main surface 10a (see FIG. 2) of the substrate 10. The optical functional layer 20 includes an optical input port 121-1i to which visible light emitted from a visible light laser light source can be input, a light incident side waveguide 121-1 for guiding the visible light input from the optical input port 121-1i, an optical branching section 150-1 to which one monitor optical waveguide 141-m and three optical modulation optical waveguides 141-1, 141-2, and 141-3 are connected, and a Mach-Zehnder type optical modulation section 140 is connected between the optical branching section 150-1 and the Mach-Zehnder type optical modulation section 140. 1, a 3×2 type optical multiplexing / branching section 150-2 to which optical modulation optical waveguides 142-1 and 142-2 for connecting to each other are connected; a Mach-Zehnder type optical modulation section 140 that modulates visible light guided through the two optical modulation optical waveguides 142-1 and 142-2; a two-input, one-output (2×1 type) optical multiplexing section 150-3 that multiplexes the two visible light beams modulated by the Mach-Zehnder type optical modulation section 140; an optical output side waveguide 122-1 that guides the light multiplexed by the optical multiplexing section 150-3 to an optical output port 122-1o; an optical output port 122-1o through which the light guided through the optical output side waveguide 122-1 is output to the outside; and a monitor optical output port 141-mo through which the light guided through the monitor optical waveguide 141-m is output to a photodetector.

[0053] In the electro-optical element 101 shown in Fig. 3, the laser light input from the visible light laser light source to the optical input port 121-1i is branched into four optical waveguides by a 1-input 4-output (1x4) optical branching section 150-1, and the light guided in one of the optical waveguides is used as monitor light. In this configuration, only 1 / 4 of the intensity (Pin) of the laser light input to the optical input port 121-1i is used for monitoring (Pmonitor=1 / 4Pin), and the remaining 3 / 4 can be used for optical output (Pout=3 / 4Pin). In other words, 3 / 4 of the intensity of the input light can be used for output light, and the efficiency of the output light relative to the input light is improved to 3 / 4.

[0054] 3 has four side surfaces 101A, 101B, 101C, and 101D, and the optical input port 121-1i is provided on the first side surface 101A, the optical output port 122-1o is provided on the third side surface 101C, and the monitor optical output port 141-mo is provided on the second side surface 101B, but is not limited thereto. The optical input port 121-1i, the optical output port 122-1o, and the monitor optical output port 141-mo may be provided on the upper surface of the electro-optical element 101 using structures such as grating couplers and mirrors. In this case, the optical input port 121-1i, the optical output port 122-1o, and the monitor optical output port 141-mo do not need to be provided on the four side surfaces 101A, 101B, 101C, and 101D, and may be provided anywhere on the upper surface of the electro-optical element 101.

[0055] The optical branching unit 150-1, the 3×2 type optical multiplexing / branching unit 150-2, and the optical multiplexing unit 150-3 can be any known optical branching unit, optical multiplexing / branching unit, or optical multiplexing unit, but any of them can be a multimode interferometer (MMI). By using a multimode interferometer, it is possible to reduce efficiency degradation due to manufacturing variations.

[0056] In the electro-optical element 101 shown in FIG. 3, the light branched by the optical branching unit 150-1 is guided through three optical waveguides for optical modulation (optical waveguides 141-1, 141-2, and 141-3), but three is an example and the number is not limited to three, and the number can be more than (N1-1) (N1 is an integer of 3 or more). In this configuration, of the intensity (Pin) of the laser light input to the optical input port 121-1i, only 1 / N1 is used for monitoring (Pmonitor=1 / N1Pin), and the remaining (N1-1) / N1 can be used for optical output (Pout=(N1-1) / N1Pin). That is, the intensity (N1-1) / N1 of the input light can be used for output light, and the efficiency of the output light relative to the input light is improved to (N1-1) / N1.

[0057] 4 is a plan view schematic diagram showing an electro-optical element according to a third embodiment. In the following, illustrations and descriptions of parts common to the electro-optical elements according to the above embodiments may be omitted.

[0058] The electro-optical element 102 shown in FIG. 4 includes a substrate 10 (see FIG. 2) and an optical functional layer 20 (see FIG. 2) formed on the main surface 10a (see FIG. 2) of the substrate 10. The optical functional layer 20 includes an optical input port 221-1i to which visible light emitted from a visible laser light source can be input, a light incident side waveguide 221-1 that guides the visible light input from the optical input port 221-1i, and one monitor. an optical branching section 250-1 in which a switch optical waveguide 241-m and four optical modulation optical waveguides 241-11, 241-12, 241-21, and 241-22 are connected; and an optical branching section 250-1 in which optical modulation optical waveguides 241-11, 241-12, 241-21, and 241-22 are connected to the input side between the optical branching section 250-1 and the Mach-Zehnder type optical modulation section 240 and a Mach-Zehnder type optical modulation section 241-m and four optical modulation optical waveguides 241-11, 241-12, 241-21, and 241-22 are connected to the input side and The optical waveguides for optical modulation 242-1 and 242-2 are connected to the two 2×1 type optical multiplexing / branching units 250-21 and 250-22, a Mach-Zehnder type optical modulation unit 240 that modulates the visible light guided through the two optical waveguides for optical modulation 242-1 and 242-2, and a two-input, one-output type (2×1 type) optical multiplexing / branching unit 250-21 and 250-22 that multiplexes the two visible light modulated by the Mach-Zehnder type optical modulation unit 240. the optical output side waveguide 222-1 that guides the light multiplexed in the optical multiplexing section 250-3 to the optical output port 222-1o, the optical output port 222-1o from which the light that has been guided through the optical output side waveguide 222-1 is output to the outside, and a monitor optical output port 241-mo from which the light that has been guided through the monitor optical waveguide 241-m is output toward the photodetector.

[0059] In the electro-optical element 102 shown in Fig. 4, the laser light input from the visible light laser light source to the optical input port 221-1i is branched into five optical waveguides by a 1-input 5-output (1x5) optical branching section 250-1, and the light guided in one of the optical waveguides is used as monitor light. In this configuration, only 1 / 5 of the intensity (Pin) of the laser light input to the optical input port 221-1i is used for monitoring (Pmonitor=1 / 5Pin), and the remaining 4 / 5 can be used for optical output (Pout=4 / 5Pin). In other words, 4 / 5 of the intensity of the input light can be used for output light, and the efficiency of the output light relative to the input light is improved to 4 / 5.

[0060] 4 has four side surfaces 102A, 102B, 102C, and 102D, and the optical input port 221-1i is provided on the first side surface 102A, the optical output port 222-1o is provided on the third side surface 102C, and the monitor optical output port 241-mo is provided on the second side surface 102B, but is not limited thereto. The optical input port 221-1i, the optical output port 222-1o, and the monitor optical output port 241-mo may be provided on the upper surface of the electro-optical element 102 using structures such as grating couplers and mirrors. In this case, the optical input port 221-1i, the optical output port 222-1o, and the monitor optical output port 241-mo do not need to be provided on the four side surfaces 102A, 102B, 102C, and 102D, and may be provided anywhere on the upper surface of the electro-optical element 102.

[0061] The optical branching unit 250-1, the two 2×1 type optical multiplexing / branching units 250-21 and 250-22, and the optical multiplexing unit 250-3 can be any known optical branching unit, optical multiplexing / branching unit, or optical multiplexing unit, but any of them can be a multimode interferometer (MMI). By using a multimode interferometer, it is possible to reduce efficiency degradation due to manufacturing variations.

[0062] Both of the two optical multiplexing / branching units 250-21 and 250-22 are 2×1 type optical multiplexing / branching units, but when the optical branching unit 250-1 is configured to output to (2N2×1) optical waveguides, there are two N2×1 type optical multiplexing / branching units.

[0063] 4, there are four optical waveguides for optical modulation (optical waveguides for optical modulation 241-11, 241-12, 241-21, 241-22) through which the light branched by the optical branching unit 250-1 is guided, but four is only an example and the number is not limited to four, and the number can be 2N2 or more (N2 is an integer equal to or greater than 2). In this configuration, of the intensity (Pin) of the laser light input to the optical input port 221-1i, only 1 / (2N2+1) is used for monitoring (Pmonitor=1 / (2N2+1)Pin), and the remaining 2N2 / (2N2+1) can be used for optical output (Pout=2N2 / (2N2+1)Pin). In other words, 2N2 / (2N2+1) of the intensity of the input light can be used for the output light, and the efficiency of the output light relative to the input light is improved to 2N2 / (2N2+1).

[0064] FIG. 5A is a schematic plan view showing a modified example of the electro-optical element according to the first embodiment. In the following, illustrations and descriptions of parts common to the electro-optical element according to the above embodiment may be omitted. The electro-optical element described with reference to FIGS. 1 and 2 has one optical input port and one optical output port, and is configured to modulate visible light output from one visible light laser light source. However, this modified example has three optical input ports capable of inputting three visible lights with different wavelengths output from three visible light laser light sources, and three optical output ports that output the three visible lights with different wavelengths to the outside. In the following, an example will be described in which the three visible lights with different wavelengths are visible lights output from a visible light laser light source of three colors, RGB.

[0065] Here, the red (R) laser light can be light with a peak wavelength of 600 nm to 830 nm, the green (G) laser light can be light with a peak wavelength of 500 nm to 600 nm, and the blue (R) laser light can be light with a peak wavelength of 380 nm to 500 nm.

[0066] The electro-optical element 200 shown in FIG. 5A includes a substrate 10 (see FIG. 2) and an optical function layer 20 (see FIG. 2) formed on a major surface 10a of the substrate 10 (see FIG. 2). The optical functional layer 20 includes an optical input port 21-1i to which visible light emitted from a red laser light source can be input, a light incident side waveguide 21-1 that guides the red laser light input from the optical input port 21-1i, an optical branching section 50-11 in which one monitor optical waveguide 41-m and two optical modulation optical waveguides 41-11 and 41-12 are connected, a Mach-Zehnder type optical modulation section 40-1 that modulates the red laser light guided through the two optical modulation optical waveguides 41-11 and 41-12, and a Mach-Zehnder type optical The optical multiplexer 50-21 has a two-input, one-output type (2×1 type) that multiplexes two red laser beams modulated by the modulator 40-1, an optical output side waveguide 22-1 that guides the red laser beam multiplexed by the optical multiplexer 50-21 to an optical output port 22-1o, an optical output port 22-1o through which the red laser beam that has been guided through the optical output side waveguide 22-1 is output to the outside, and a monitor optical output port 41-mo through which the red laser beam that has been guided through the monitor optical waveguide 41-m is output toward a photodetector. The optical functional layer 20 further includes an optical input port 21-2i capable of inputting visible light emitted from a green laser light source, a light incident side waveguide 21-2 for guiding the green laser light input from the optical input port 21-2i, an optical branching section 50-12 in which one monitor optical waveguide 42-m and two optical modulation optical waveguides 41-21 and 41-22 are connected, a Mach-Zehnder type optical modulation section 40-2 for modulating the green laser light guided through the two optical modulation optical waveguides 41-21 and 41-22, and a Mach-Zehnder type optical modulation section 40-2 for modulating the green laser light guided through the two optical modulation optical waveguides 41-21 and 41-22. the optical output side waveguide 22-2 for guiding the green laser light multiplexed by the optical multiplexing unit 50-22 to an optical output port 22-2o; and a monitor optical output port 42-mo for outputting the green laser light that has been guided through the monitor optical waveguide 42-m toward a photodetector. The optical functional layer 20 further includes an optical input port 21-3i to which visible light emitted from a blue laser light source can be input, a light incident side waveguide 21-3 for guiding the blue laser light input from the optical input port 21-3i, an optical branching section 50-13 in which one monitor optical waveguide 43-m and two optical modulation optical waveguides 41-31 and 41-32 are connected, a Mach-Zehnder type optical modulation section 40-3 for modulating the blue laser light guided through the two optical modulation optical waveguides 41-31 and 41-32, and a Mach-Zehnder type optical modulation section 40-2 for modulating the blue laser light guided through the two optical modulation optical waveguides 41-31 and 41-32. the optical output side waveguide 22-3 for guiding the blue laser light multiplexed by the optical multiplexing unit 50-23 to an optical output port 22-3o; the optical output port 22-3o from which the blue laser light guided through the optical output side waveguide 22-3 is output to the outside; and a monitor optical output port 43-mo from which the blue laser light guided through the monitor optical waveguide 43-m is output toward a photodetector.

[0067] In the electro-optical element 200 shown in Fig. 5A, the red laser light input from the red laser light source to the optical input port 21-1i is branched into three optical waveguides by a 1-input 3-output (1x3) optical branching unit 50-11, and the light guided in one of the optical waveguides is used as monitor light. In this configuration, only 1 / 3 of the intensity (Pin) of the red laser light input to the optical input port 21-1i is used for monitoring (Pmonitor=1 / 3Pin), and the remaining 2 / 3 can be used for optical output (Pout=2 / 3Pin). In other words, 2 / 3 of the intensity of the input light of the red laser can be used for output light, and the efficiency of the output light relative to the input light is improved to 2 / 3. Similarly, green laser light input from a green laser light source to optical input port 21-2i is branched into three optical waveguides by a 1-input, 3-output (1x3) optical branching unit 50-12, and the light guided through one of the optical waveguides is used as monitor light. In this configuration, only 1 / 3 of the intensity (Pin) of the green laser light input to optical input port 21-2i is used for monitoring (Pmonitor=1 / 3Pin), and the remaining 2 / 3 can be used for optical output (Pout=2 / 3Pin). In other words, 2 / 3 of the intensity of the input light of the green laser can be used for output light, and the efficiency of the output light relative to the input light is improved to 2 / 3. Similarly, the blue laser light input from the blue laser light source to the optical input port 21-3i is branched into three optical waveguides by a 1-input 3-output (1x3) optical branching unit 50-13, and the light guided in one of the optical waveguides is used as monitor light. In this configuration, only 1 / 3 of the intensity (Pin) of the blue laser light input to the optical input port 21-3i is used for monitoring (Pmonitor=1 / 3Pin), and the remaining 2 / 3 can be used for optical output (Pout=2 / 3Pin). In other words, 2 / 3 of the intensity of the input light of the blue laser can be used for output light, and the efficiency of the output light relative to the input light is improved to 2 / 3.

[0068] 5A has four side surfaces 200A, 200B, 200C, and 200D, and the optical input ports 21-1i, 21-2i, and 21-3i are provided on the first side surface 200A, the optical output ports 22-1o, 22-2o, and 22-3o are provided on the third side surface 200C, and the monitor optical output ports 41-mo, 42-mo, and 43-mo are provided on the second side surface 200B, but are not limited thereto. The optical input ports 21-1i, 21-2i, and 21-3i, the optical output ports 22-1o, 22-2o, and 22-3o, and the monitor optical output ports 41-mo, 42-mo, and 43-mo may be provided with structures such as grating couplers or mirrors to input and output light to and from the upper surface of the electro-optical element 200. In this case, the optical input ports 21-1i, 21-2i, 21-3i, the optical output ports 22-1o, 22-2o, 22-3o and the monitor optical output ports 41-mo, 42-mo, 43-mo do not need to be provided on the four side surfaces 200A, 200B, 200C, 200D, and may be provided anywhere on the top surface of the electro-optical element 200.

[0069] The optical branching units 50-11, 50-12, and 50-13 and the optical multiplexing units 50-21, 50-22, and 50-23 can be any known optical branching unit and optical multiplexing unit, but any of them can be a multimode interferometer (MMI). By using a multimode interferometer, it is possible to reduce efficiency degradation due to manufacturing variations.

[0070] In the electro-optical element 200 shown in FIG. 5A, there are two optical waveguides for optical modulation that guide the light branched at the optical branching section 50-11, two optical waveguides for optical modulation that guide the light branched at the optical branching section 50-12, and two optical waveguides for optical modulation that guide the light branched at the optical branching section 50-13, but two is just an example and the number is not limited to two, and the number can be three or more.

[0071] The above describes an electro-optical element that enables modulation of three different wavelengths of visible light as a modified example of the electro-optical element according to the first embodiment. Similarly, for the electro-optical element according to the second embodiment and the electro-optical element according to the third embodiment, an electro-optical element that enables modulation of three different visible light can be fabricated based on an electro-optical element that enables modulation of visible light of one wavelength.

[0072] FIG. 5B is a schematic plan view showing another modified example of the electro-optical element according to the first embodiment. In the following, illustrations and descriptions of parts common to the electro-optical element may be omitted. In the example shown in FIG. 5A, three optical output ports for outputting three visible lights with different wavelengths to the outside are provided, and each visible light is output from the three optical output ports. On the other hand, the example shown in FIG. 5B is provided with a multiplexing section for multiplexing three visible lights with different wavelengths, and one optical output port for outputting the multiplexed light to the outside, and is configured to multiplex and then output three visible lights with different wavelengths. In the following, an example will be described in which the three visible lights with different wavelengths are visible lights output from a visible light laser light source of three colors of RGB.

[0073] The electro-optical element 201 shown in FIG. 5B includes a substrate 10 (see FIG. 2) and an optical function layer 20 (see FIG. 2) formed on the main surface 10a of the substrate 10 (see FIG. 2). In addition to the same configuration as the electro-optical element 200 shown in FIG. 5A, the optical functional layer 20 includes a three-input, one-output type optical multiplexing section 50-31 that uses as inputs an optical output side waveguide 22-1 that guides the red laser light multiplexed in the optical multiplexing section 50-21, an optical output side waveguide 22-2 that guides the green laser light multiplexed in the optical multiplexing section 50-22, and an optical output side waveguide 22-3 that guides the blue laser light multiplexed in the optical multiplexing section 50-23, and multiplexes these RGB laser lights and outputs them to the optical output side waveguide 23-1, and an optical output port 23-1o that outputs the combined RGB light that has been guided through the optical output side waveguide 23-1 to the outside.

[0074] 5B is the same as the electro-optical element 200 shown in Fig. 5A in that the light intensity branched as monitor light for each of the RGB laser lights is only 1 / 3 of the intensity (Pin) of each of the RGB laser lights input to each light input port (Pmonitor=1 / 3Pin). Therefore, like the electro-optical element 200 shown in Fig. 5A, 2 / 3 of the input light intensity of each of the RGB laser lights can be used as output light, and the efficiency of the output light relative to the input light is improved to 2 / 3.

[0075] 5B has four side surfaces 201A, 201B, 201C, and 201D, and optical input ports 21-1i, 21-2i, and 21-3i are provided on the first side surface 201A, optical output port 23-1o is provided on the third side surface 201C, and monitor optical output ports 41-mo, 42-mo, and 43-mo are provided on the second side surface 201B, but is not limited thereto. A structure such as a grating coupler or a mirror may be used for the optical input ports 21-1i, 21-2i, and 21-3i, the optical output port 23-1o, and the monitor optical output ports 41-mo, 42-mo, and 43-mo to input and output light to and from the upper surface of the electro-optical element 201. In this case, the optical input ports 21-1i, 21-2i, 21-3i, the optical output port 23-1o and the monitor optical output ports 41-mo, 42-mo, 43-mo do not need to be provided on the four side surfaces 201A, 201B, 201C, 201D, and may be provided anywhere on the top surface of the electro-optical element 201.

[0076] The optical multiplexer 50-31 can be a known optical branching unit and optical multiplexer, like the optical branching units 50-11, 50-12, and 50-13 and the optical multiplexers 50-21, 50-22, and 50-23, but any of them can be a multimode interferometer (MMI). By using a multimode interferometer, it is possible to reduce efficiency degradation due to manufacturing variations.

[0077] The above describes an electro-optical element that enables modulation of three different wavelengths of visible light as another variation of the electro-optical element of the first embodiment. Similarly, for the electro-optical element of the second embodiment and the electro-optical element of the third embodiment, electro-optical elements that enable modulation of three different visible light can be fabricated based on an electro-optical element that enables modulation of visible light of one wavelength.

[0078] [Light source module] 6 is a schematic plan view showing a light source module according to a fourth embodiment. In the following, illustrations and descriptions of parts common to the above-mentioned configurations may be omitted.

[0079] The light source module 300 shown in Figure 6 includes the electro-optical element 100 shown in Figure 1, a visible light laser light source 30 that outputs visible light input from an optical input port 21-1i, and a laser light intensity control unit 80 that detects monitor light from a monitor light output port 41-mo with a photodetector 70 and adjusts the intensity of the laser light emitted from the visible light laser light source 30 in accordance with the detected light intensity.

[0080] 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 830 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.

[0081] The photodetector 70 may be a known photodetector.

[0082] The laser light intensity control unit 80 can use a known control system that controls the driving current of the visible light laser source 30 to control the laser light intensity based on a signal of the light intensity of the monitor light detected by the photodetector 70.

[0083] In the light source module 300 shown in FIG. 6, it is possible to use both current modulation in the visible laser light source and voltage modulation in the Mach-Zehnder type optical modulation section.

[0084] 7 is a schematic plan view showing a light source module according to embodiment 5. In the following, illustrations and descriptions of parts common to the above-mentioned configurations may be omitted.

[0085] The light source module 301 shown in Figure 7 includes the electro-optical element 101 shown in Figure 3, a visible light laser light source 30 that outputs visible light input from an optical input port 121-1i, and a laser light intensity control unit 80 that detects monitor light from a monitor light output port 141-mo using a photodetector 70 and adjusts the intensity of the laser light emitted from the visible light laser light source 30 in accordance with the detected light intensity.

[0086] 6, the light source module 301 shown in FIG. 7 can also use both current modulation in the visible laser light source and voltage modulation in the Mach-Zehnder type optical modulation section.

[0087] 8 is a schematic plan view showing a light source module according to embodiment 6. In the following, illustrations and descriptions of parts common to the above-mentioned configurations may be omitted.

[0088] The light source module 302 shown in Figure 8 includes the electro-optical element 102 shown in Figure 4, a visible light laser light source 30 that outputs visible light input from an optical input port 221-1i, and a laser light intensity control unit 80 that detects monitor light from a monitor light output port 241-mo using a photodetector 70 and adjusts the intensity of the laser light emitted from the visible light laser light source 30 in accordance with the detected light intensity.

[0089] As with the light source module 300 shown in FIG. 6 and the light source module 301 shown in FIG. 7, the light source module 302 shown in FIG. 8 can use both current modulation in the visible light laser light source and voltage modulation in the Mach-Zehnder type optical modulation section.

[0090] 9A is a schematic plan view showing a modified example of the light source module according to the fourth embodiment. In the following, illustrations and descriptions of parts common to the above-mentioned configurations may be omitted.

[0091] The light source module 400 shown in FIG. 9A includes the electro-optical element 200 shown in FIG. 5A, a red laser light source 30-1 that outputs red laser light input from the optical input port 21-1i, a green laser light source 30-2 that outputs green laser light input from the optical input port 21-2i, a blue laser light source 30-3 that outputs blue laser light input from the optical input port 21-3i, and a laser light intensity control unit 180 that detects monitor light from each of the monitor light output ports 41-mo, 42-mo, and 43-mo using a photodetector 170, and can independently adjust the light intensity of each laser light emitted from the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 according to the light intensity of each detected laser light. As described above, the light source module 400 shown in Fig. 9A includes the electro-optical element 200 shown in Fig. 5A as an electro-optical element. In Fig. 9A, components denoted by the reference symbols used in Fig. 5A are common, and description thereof will be omitted.

[0092] Various laser elements can be used as the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3. For example, commercially available laser diodes (LDs) emitting red light, green light, blue light, etc. can be used. In the light source module 400, the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 are arranged at intervals from each other in a direction approximately perpendicular to the emission direction of the light emitted from each laser light source, and are provided on the upper surface of the subcarrier 120.

[0093] When the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 are, for example, laser diodes, they can be mounted as bare chips on the subcarrier 120. The subcarrier 120 is made of, for example, aluminum nitride (AlN), aluminum oxide (Al2O3), silicon (Si), or the like.

[0094] The subcarrier 120 can be directly bonded to the substrate 10 via a metal bonding layer. This configuration allows further miniaturization by eliminating spatial coupling and fiber coupling. In FIG. 9A, the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 are mounted on one subcarrier 120, but each light source may be mounted on a separate subcarrier. 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 light source coincide with the axes of the light incident side waveguide 21-1, the light incident side waveguide 21-2, and the light incident side waveguide 21-3, respectively (active alignment).

[0095] The photodetector 170 may be a known photodetector.

[0096] The laser light intensity control unit 180 can use a known control system that controls the drive current of the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 to control the laser light intensity based on the light intensity signal of each monitor light detected by the photodetector 170.

[0097] The light emission surfaces of the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 (in FIG. 9A, the light emission surface of the red laser light source 30-1 is indicated by reference symbol 31) and the light incident surface (side surface) 200A of the electro-optical element 200 are disposed at a predetermined interval. The light incident surface 200A faces the light emission surface 31, and there is a gap S between the light emission surface 31 and the light incident surface 200A in the x direction. Since the light source module 400 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 red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 enter the incident path while satisfying a predetermined coupling efficiency. When the light source module 400 is used in XR glasses such as AR glasses and VR glasses, taking into account the amount of light required for the XR glasses such as AR glasses and VR glasses, the size of the gap (spacing) S in the x-direction is, for example, greater than 0 μm and less than 5 μm.

[0098] For example, in order to display an image in a desired color in a retinal projection display, it is necessary to independently modulate the intensity of each of the three colors (RGB) that represent visible light at high speed. If such modulation is performed only by the visible laser light source (current modulation), the load on the IC that controls the modulation becomes large, but in the light source module 400 shown in FIG. 9A, it is possible to use modulation (voltage modulation) by a Mach-Zehnder type optical modulation unit in combination. In this case, rough adjustment may be performed by current (visible laser light source) and fine adjustment may be performed by voltage (Mach-Zehnder type optical modulation unit), or rough adjustment may be performed by voltage (Mach-Zehnder type optical modulation unit) and fine adjustment may be performed by current (visible laser light source). Since fine adjustment by voltage has better responsiveness, the former is adopted when responsiveness is important, and since fine adjustment by current requires a lower current and thus reduces power consumption, it is preferable to adopt the latter when reducing power consumption is important. Furthermore, the Mach-Zehnder type optical modulation unit is capable of high-speed modulation at frequencies exceeding gigahertz, so it is possible to obtain images with high resolution.

[0099] Above, a light source module that enables modulation of three different wavelengths of visible light has been described as a modified example of the light source module of the fourth embodiment. Similarly, for the electro-optical element of the fifth embodiment and the light source module of the sixth embodiment, a light source module that enables modulation of three different visible lights can be fabricated based on a light source module that enables modulation of visible light of one wavelength.

[0100] FIG. 9B is a schematic plan view showing another modified example of the light source module according to the fourth embodiment. In the following, illustrations and descriptions of parts common to the above-mentioned configuration may be omitted. In the example shown in FIG. 9A, the electro-optical element 200 has three optical output ports that output three visible lights with different wavelengths to the outside, and outputs each visible light from the three optical output ports. On the other hand, in the example shown in FIG. 9B, the electro-optical element 201 has a multiplexing section that multiplexes three visible lights with different wavelengths, and one optical output port that outputs the multiplexed light to the outside, and multiplexes the three visible lights with different wavelengths before outputting them. In the following, an example will be described in which the three visible lights with different wavelengths are visible lights output from a visible light laser light source of three colors of RGB.

[0101] The light source module 500 shown in FIG. 9B includes the electro-optical element 201 shown in FIG. 5B, a red laser light source 30-1 that outputs red laser light input from the optical input port 21-1i, a green laser light source 30-2 that outputs green laser light input from the optical input port 21-2i, a blue laser light source 30-3 that outputs blue laser light input from the optical input port 21-3i, and a laser light intensity control unit 180 that detects monitor light from each of the monitor light output ports 41-mo, 42-mo, and 43-mo using a photodetector 170, and can independently adjust the light intensity of each laser light emitted from the red laser light source 30-1, the green laser light source 30-2, and the blue laser light source 30-3 according to the light intensity of each detected laser light.

[0102] As described above, the light source module 500 shown in Fig. 9B includes the electro-optical element 200 shown in Fig. 5B as an electro-optical element. In Fig. 9B, components denoted by the reference symbols used in Fig. 5B are common, and description thereof will be omitted.

[0103] [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.

[0104] 10 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 glasses frame 10010. Reference character L denotes image display light.

[0105] 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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] The optical engine 5001 includes a laser driver 1100, an optical scanning mirror driver 1200, and a video controller 1300 that controls these drivers.

[0110] [XR Glasses] The XR glasses according to this embodiment are equipped with any of the light source modules according to the above embodiments. XR glasses are glasses-type devices, and XR is a general term for virtual reality (VR), augmented reality (AR), and mixed reality.

[0111] FIG. 10 is a conceptual diagram for explaining the XR glasses according to this embodiment. 10, the XR glasses 10000 have a visible light source module 1001 mounted on a frame 10010. Reference character L denotes an image display light.

[0112] 10, the visible light source module 1001, the optical scanning mirror 3001, and the optical system 2001 connecting the visible light source module 1001 and the optical scanning mirror 3001 may be collectively referred to as an optical engine 5001. As the visible light source module 1001, the light source module according to the above-described embodiment is used.

[0113] The light source in the visible light source module 1001 may be, for example, one having RGB laser light sources: a red laser light source 60-1, a green laser light source 60-2, and a blue laser light source 60-3. As shown in FIG. 11, laser light emitted from a visible light source module 1001 attached to an eyeglass frame is reflected by a light scanning mirror 3001 and enters a person's eyeball E, so that an image (video) can be directly projected onto a retina M. By providing an eye-tracking mechanism, an image is projected directly onto the retina while performing eye tracking. A known eye-tracking mechanism can be used.

[0114] 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).

[0115] A collimator lens 2001a, a slit 2001b, and an ND filter 2001c are included as an optical system 2001 that optically processes the laser light emitted from the visible light source module 1001. This optical system is just one example, and other configurations may be used.

[0116] 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

[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] (Experimental Example 1) For the 1-input 3-output type optical branching unit shown in Fig. 1, the efficiency (Pout / Pin) of the output optical intensity (Pout) relative to the input optical intensity (Pin) and the ratio (Pmonitor / Pin) of the monitor optical intensity relative to the input optical intensity (Pin) were calculated for each of RGB by simulation using the parameters shown in Figs. 12A to 12C. The output optical intensity is the sum of the optical intensities output from the two optical waveguides for optical modulation (corresponding to symbols 41-1 and 41-2 in Fig. 1), and the monitor optical intensity is the optical intensity output from the optical waveguide for monitoring (corresponding to symbol 41-m in Fig. 1). Fimmwave (Photon Design) was used as the simulation software. The wavelengths of RGB were set to 637 nm, 520 nm, and 455 nm, respectively.

[0119] As shown in FIG. 12A, the length of a 1-input, 3-output optical branching section (corresponding to reference symbol 50-1 in FIG. 1) is L and its width is W. By adjusting L and W, L and W were determined so that Pout / Pin and Pmonitor / Pin were approximately 2 / 3 and 1 / 3, respectively. 12B is a schematic cross-sectional view taken along line AA in FIG. 12A, and FIG. 12C is a schematic cross-sectional view taken along line BB in FIG. 12A.

[0120] The materials were sapphire for the substrate (corresponding to reference numeral 10 in FIG. 2), lithium niobate film for the waveguide core film (corresponding to reference numeral 24 in FIG. 2), and SiO2 film for the waveguide clad film (corresponding to reference numeral 25 in FIG. 2). The shapes and dimensions of the 1-input 3-output type optical branching section, the light incident side waveguide (corresponding to reference symbol 21-1 in FIG. 1), the monitor optical waveguide (corresponding to reference symbol 41-m in FIG. 1), and the optical modulation optical waveguide (corresponding to reference symbols 41-1 and 41-2 in FIG. 1) connected to the 1-input 3-output type optical branching section were set as shown in FIG. 12A to FIG. 12C. As for the shapes, the 1-input 3-output type optical branching section, the light incident side waveguide, the monitor optical waveguide, and the optical modulation optical waveguide all had a trapezoidal cross section and were configured to have a slab with a thickness of 0.15 μm. The width of the upper base of the light incident side waveguide, the monitor optical waveguide, and the optical modulation optical waveguide was 2 μm, the inclination angle of the side surface was 80°, and the thickness (height) from the main surface of the substrate 10 (corresponding to reference symbol 10A in FIG. 2) was 0.7 μm. The interval between the monitor optical waveguide and the two optical modulation optical waveguides was set to 4 μm. Table 1 shows the length and width of the obtained 1-input 3-output type optical branching section, as well as Pout / Pin and Pmonitor / Pin.

[0121] [Table 1]

[0122] As shown in Table 1, for any of the RGB visible lights, when the width W of the 1-input 3-output type optical branching section is 12 μm, the optical output efficiency (Pout / Pin) and the monitor light ratio (Pmonitor / Pin) can be set to 0.66 and 0.33 by setting the length L to 169 μm, 212 μm, and 246 μm. From the above results, it was found that by using the electro-optical element shown in FIG. 5A, it is possible to reduce Pout / Pin and Pmonitor / Pin to approximately 2 / 3 and 1 / 3, respectively, for all of the RGB visible light.

[0123] (Experimental Example 2) For the 1-input 4-output type optical branching section shown in FIG. 3, the efficiency (Pout / Pin) of the output light intensity (Pout) relative to the input light intensity (Pin) and the ratio (Pmonitor / Pin) of the monitor light intensity to the input light intensity (Pin) were calculated for R by simulation using the parameters shown in FIGS. 13A to 13C.

[0124] As shown in FIG. 13A, the length of a 1-input 4-output type optical branching section (corresponding to reference symbol 150-1 in FIG. 3) is L and its width is W. By adjusting L and W, L and W were determined so that Pout / Pin and Pmonitor / Pin were approximately 3 / 4 and 1 / 4, respectively. 13B is a schematic cross-sectional view taken along line AA in FIG. 13A, and FIG. 13C is a schematic cross-sectional view taken along line BB in FIG. 13A.

[0125] The shapes and dimensions of the 1-input 4-output type optical branching section, the light incident side waveguide (corresponding to reference numeral 121-1 in FIG. 3), the monitor optical waveguide (corresponding to reference numeral 141-m in FIG. 3), and the optical modulation optical waveguide (corresponding to reference numerals 141-1, 141-2, and 141-3 in FIG. 3) connected to the 1-input 4-output type optical branching section were set as shown in FIG. 13A to FIG. 13C. As for the shapes, the 1-input 4-output type optical branching section, the light incident side waveguide, the monitor optical waveguide, and the optical modulation optical waveguide all had a trapezoidal cross section and a 0.15 μm thick slab. The width of the upper base of the light incident side waveguide, the monitor optical waveguide, and the optical modulation optical waveguide was 2 μm, the inclination angle of the side surface was 80°, and the thickness (height) from the main surface of the substrate 10 (corresponding to reference numeral 10A in FIG. 2) was 0.7 μm. The intervals between the monitor optical waveguide and the three optical modulation optical waveguides were set to 4 μm. Table 2 shows the length and width of the obtained 1-input 4-output type optical branching section, as well as Pout / Pin and Pmonitor / Pin.

[0126] [Table 2]

[0127] As shown in Table 2, for R, when the width W of the 1-input 4-output type optical branching section is 16 μm, by setting the length L to 223 μm, the optical output efficiency (Pout / Pin) and the monitor light ratio (Pmonitor / Pin) can be set to 0.74 and 0.24.

[0128] (Experimental Example 3) For the 1-input 5-output type optical branching section shown in FIG. 4, the efficiency (Pout / Pin) of the output light intensity (Pout) relative to the input light intensity (Pin), and the ratio (Pmonitor / Pin) of the monitor light intensity to the input light intensity (Pin) were calculated for R by simulation using the parameters shown in FIGS. 14A to 14C.

[0129] As shown in FIG. 14A, the length of a 1-input 5-output optical branching section (corresponding to reference symbol 150-1 in FIG. 4) is L and its width is W. By adjusting L and W, L and W were determined so that Pout / Pin and Pmonitor / Pin were approximately 3 / 4 and 1 / 4, respectively. 14B is a schematic cross-sectional view taken along line AA in FIG. 14A, and FIG. 14C is a schematic cross-sectional view taken along line BB in FIG. 14A.

[0130] The shapes and dimensions of the 1-input 5-output type optical branching section, the light incident side waveguide (corresponding to reference numeral 221-1 in FIG. 4), the monitor optical waveguide (corresponding to reference numeral 41-m in FIG. 4), and the optical modulation optical waveguide (corresponding to reference numerals 241-11, 241-12, 241-21, 241-22 in FIG. 4) connected to the 1-input 5-output type optical branching section were set as shown in FIG. 14A to FIG. 14C. As for the shapes, the 1-input 5-output type optical branching section, the light incident side waveguide, the monitor optical waveguide, and the optical modulation optical waveguide all had a trapezoidal cross section and were configured to have a slab of 0.15 μm thickness. The width of the upper base of the light incident side waveguide, the monitoring optical waveguide, and the optical modulation optical waveguide was 2 μm, the inclination angle of the side was 80°, and the thickness (height) from the main surface of the substrate 10 (corresponding to the symbol 10A in FIG. 2) was 0.7 μm. The intervals between the monitoring optical waveguide and the four optical modulation optical waveguides were 4 μm. Table 2 shows the length and width of the obtained 1-input 5-output type optical branching section, as well as Pout / Pin and Pmonitor / Pin.

[0131] [Table 3]

[0132] As shown in Table 3, for R, when the width W of the 1-input 5-output type optical branching section is 20 μm, by setting the length L to 278 μm, the optical output efficiency (Pout / Pin) and the monitor light ratio (Pmonitor / Pin) can be set to 0.79 and 0.19. [Explanation of symbols]

[0133] 10 Substrate 20 Optical functional layer 30 Visible light laser source 40 Mach-Zehnder type optical modulator 50-1, 150-1, 250-1 Optical branching section 150-2, 250-2 Optical multiplexer / splitter 50-2, 150-3, 250-3 Optical multiplexer 100, 101, 102, 200 Electro-optical element 300, 301, 302, 400, 1001 Light Source Module 5001 Optical Engine 10000 XR Glasses

Claims

1. A substrate; An optical function layer formed on a main surface of the substrate, The optical functional layer is an optical input port capable of inputting visible light emitted from a visible light laser light source; a light input side waveguide for guiding visible light inputted from the light input port, and an optical branching section in which one monitoring optical waveguide and a plurality of optical modulation optical waveguides are connected; a Mach-Zehnder type optical modulation section that modulates visible light guided through the plurality of optical waveguides for optical modulation; an optical multiplexing unit that multiplexes two visible lights modulated by the Mach-Zehnder type optical modulation unit; an optical output side waveguide that guides the light multiplexed by the optical multiplexing unit to an optical output port; an optical output port through which the light guided through the optical output side waveguide is output to the outside; a monitor light output port through which the light guided through the monitor optical waveguide is output toward a photodetector.

2. 2. The electro-optical element according to claim 1, wherein the plurality of optical waveguides for optical modulation are two optical waveguides for optical modulation.

3. The electro-optical element according to claim 2 , wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

4. 4. The electro-optical element according to claim 3, wherein the optical branching section and the optical multiplexing section each constitute a multimode interferometer.

5. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; The electro-optical element according to claim 4 , further comprising: three optical output ports for outputting three visible light beams having different wavelengths to the outside.

6. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; an optical multiplexing unit that multiplexes three visible light beams having different wavelengths; The electro-optical element according to claim 4 , further comprising: one optical output port that outputs the light multiplexed in the optical multiplexing section to an outside.

7. The plurality of optical waveguides for optical modulation are (N １ -1) Book (N １ is an integer of 3 or more), Between the optical branching unit and the Mach-Zehnder type optical modulation unit, １ (N-1) optical waveguides for optical modulation are connected, and two optical waveguides connected to the Mach-Zehnder type optical modulation unit are connected to the output side. １ 2. The electro-optical element according to claim 1, further comprising a -1)×2 type optical multiplexer / split section.

8. The electro-optical element according to claim 7 , wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

9. 9. The electro-optic element according to claim 8, wherein the optical branching section and the optical multiplexing section each constitute a multimode interferometer.

10. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; The electro-optical element according to claim 9 , further comprising: three optical output ports for outputting three visible light beams having different wavelengths to the outside.

11. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; an optical multiplexing unit that multiplexes three visible light beams having different wavelengths; The electro-optical element according to claim 9 , further comprising: one optical output port that outputs the light multiplexed in the optical multiplexing section to the outside.

12. The plurality of optical waveguides for optical modulation are 2N ２ Book (N ２ is an integer of 2 or more), Between the optical branching unit and the Mach-Zehnder type optical modulation unit, two N ２ x1 type optical branching unit, The two N ２ Each of the ×1 type optical splitters has a 2N ２ Of the optical waveguides for optical modulation, N ２ 2. The electro-optic element according to claim 1, further comprising: an optical waveguide for optical modulation connected to said first optical waveguide; and an optical waveguide connected to said Mach-Zehnder type optical modulation section on the output side.

13. The electro-optical element according to claim 12 , wherein the substrate is made of a material different from lithium niobate, and the optical function layer is made of lithium niobate.

14. 14. The electro-optic element according to claim 13, wherein the optical branching section and the optical multiplexing section each constitute a multimode interferometer.

15. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; The electro-optical element according to claim 14 , further comprising: three optical output ports for outputting three visible light beams having different wavelengths to the outside.

16. Three optical input ports capable of receiving three visible light beams having different wavelengths output from three visible light laser light sources; an optical multiplexing unit that multiplexes three visible light beams having different wavelengths; The electro-optical element according to claim 14 , further comprising: one optical output port that outputs the light multiplexed in the optical multiplexing section to the outside.

17. 16. A light source module comprising: an electro-optical element according to claim 1; a visible light laser light source that outputs visible light input from the optical input port; and a laser light intensity control unit that detects monitor light from the monitor light output port with a photodetector and adjusts the intensity of the laser light emitted from the visible light laser light source in accordance with the detected light intensity.

18. 17. A light source module comprising: an electro-optical element according to claim 6; a visible light laser light source that outputs visible light input from the optical input port; and a laser light intensity control unit that detects monitor light from the monitor light output port with a photodetector and adjusts the intensity of the laser light emitted from the visible light laser light source in accordance with the detected light intensity.

19. An optical engine comprising the light source module according to claim 17 mounted thereon.

20. An optical engine comprising the light source module according to claim 18 mounted thereon.

21. XR glasses equipped with the light source module according to claim 17.

22. XR glasses equipped with the light source module according to claim 18.

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