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

Abstract

To provide an electro-optical element capable of forming a light source module that achieves a high ratio of an intensity of output light to an intensity of light incident from a light source to an optical waveguide.SOLUTION: An electro-optical element 100 includes a substrate and an optical function layer formed on a main surface of the substrate. The optical function layer has: a light incident side optical waveguide 21 that guides light emitted from a light source; an optical branch portion 51 that branches the light incident side optical waveguide 21 into two optical modulation optical waveguides 21a and 21b; a Mach-Zehnder optical modulation portion 40 that modulates light guided through the two optical modulation optical waveguides 21a and 21b; an optical coupling and branch portion 52 that branches the two optical modulation optical waveguides 21c and 21d guiding modulated light modulated by the Mach-Zehnder optical modulation portion 40 into one monitoring optical waveguide 3 and a plurality of light output side optical waveguides 21e and 21f; and an optical coupling portion 53 that makes the plurality of light output side optical waveguides 21e and 21f as one light output optical waveguide 22.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 technologies such as VR (Virtual Reality) and AR (Augmented Reality). In recent years, retinal scanning displays, which allow users to view images by focusing two-dimensionally scanned light on the user's retina, have been attracting particular attention as glasses-type terminals.

[0003] Generally, in a retinal scanning display, three colors of visible light emitted from a light source are combined onto 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 incident on the user's pupil. This incident light forms an image on the user's retina, allowing the user to view the image. In this case, the retina is the screen on which the image is displayed.

[0004] Some XR glasses, such as retinal scanning displays, are equipped with a light source module that includes a light source and an electro-optical element into which the light emitted from the light source is incident. The light source may be an LED (Light Emitting Diode) or an LD (Laser Diode) that emits light of wavelengths corresponding to the colors R (red), G (green), and B (blue). The electro-optical element may have an optical waveguide made of lithium niobate (LiNbO3).

[0005] Patent Document 1 describes an optical modulator having a substrate having an electro-optic effect, including a first optical waveguide into which a first light is incident, a second optical waveguide into which a second light having a longer wavelength than the first light is incident, and a third optical waveguide into which a third light having a longer wavelength than the second light is incident.

[0006] Patent Document 2 describes an optical waveguide element having a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a light receiving element disposed on the substrate for monitoring light waves propagating through the optical waveguide or light waves radiated from the optical waveguide. The optical waveguide element described in Patent Document 2 includes a monitoring optical waveguide extending from the optical waveguide to the light receiving element. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6728596 [Patent Document 2] Patent Publication No. 2021-162642 Summary of the Invention [Problem to be solved by the invention]

[0008] The amount of light emitted from a light source such as an LD (laser diode) varies with temperature. Therefore, in a light source module that includes a light source such as an LD and an electro-optical element to which the light emitted from the light source is incident, the intensity (amount of light) of the output light emitted from the electro-optical element varies with temperature. In addition, when the electro-optical element of the light source module has an optical waveguide made of lithium niobate (LiNbO3), the modulation waveform changes (DC drift) with the passage of time when a DC (direct current) voltage that changes the refractive index of the optical waveguide is applied.

[0009] For this reason, in conventional light source modules, modulated light produced by an electro-optic element is split into two, monitor light and output light, using a multimode interferometer (MMI), and the temperature-induced light intensity fluctuation and / or DC drift of the monitor light is detected by a photodetector. Then, depending on the result of the detection of the monitor light, a control unit controls the current supplied to the light source or the DC (direct current) voltage that changes the refractive index of the optical waveguide, thereby performing feedback control to control the fluctuation of the modulated light emitted from the electro-optic element.

[0010] Therefore, in conventional light source modules, in order to perform feedback control, light with half the intensity of the modulated light emitted from the electro-optic element is used as monitor light. For this reason, in conventional light source modules, the ratio of output light to light incident on the optical waveguide from the light source is low, and there has been a demand to increase the ratio of output light.

[0011] The present invention has been made in consideration of the above problems, and aims to provide an electro-optical element that can form a light source module in which the ratio of the intensity of the output light to the intensity of the light incident from the light source to the optical waveguide is high. Another object of the present invention is to provide a light source module which includes the electro-optical element of the present invention and has a high ratio of the intensity of output light to the intensity of light incident from a light source to an optical waveguide. Another object of the present invention is to provide an optical engine and XR glasses equipped with a light source module having a high ratio of the intensity of output light to the intensity of light incident from the light source to the optical waveguide. [Means for solving the problem]

[0012] An electro-optical element according to one aspect of the present invention comprises a substrate and an optical functional layer formed on a main surface of the substrate, the optical functional layer having a light incident side optical waveguide that guides light emitted from a light source, an optical branching section that branches the light incident side optical waveguide into two optical modulation optical waveguides, a Mach-Zehnder type optical modulation section that modulates light guided through the two optical modulation optical waveguides, an optical multiplexing and branching section that branches the two optical modulation optical waveguides that guide modulated light modulated by the Mach-Zehnder type optical modulation section into one monitor optical waveguide and multiple optical output side optical waveguides, and an optical multiplexing section that combines the multiple optical output side optical waveguides into one optical output optical waveguide. Effect of the Invention

[0013] The electro-optical element of the present invention includes an optical functional layer having an optical multiplexing / branching section that branches two optical waveguides for optical modulation, which guide modulated light modulated by a Mach-Zehnder type optical modulator, into one optical waveguide for monitoring and a plurality of optical waveguides on the optical output side, and an optical multiplexing section that uses the plurality of optical waveguides on the optical output side as one optical waveguide for optical output. Therefore, in the electro-optical element of the present invention, only 1 / (the number of optical waveguides on the optical output side+1) of the modulated light output from the electro-optical element is used as monitor light. Therefore, a light source module including the electro-optical element of the present invention and a light source has a small amount of light used as monitor light, and the ratio of the intensity of the output light to the intensity of the light input from the light source to the optical waveguide is high.

[0014] The light source module of the present invention includes the electro-optical element and the light source of the present invention. Also, the optical engine and the XR glasses of the present invention are equipped with the light source module of the present invention. Therefore, the light source module, the optical engine and the XR glasses of the present invention can efficiently use the light emitted from the light source. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a plan view illustrating an electro-optical element according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the electro-optical element shown in FIG. 1 taken along line XX'. [Diagram 3] FIG. 3 is a schematic plan view showing an electro-optical element according to the second embodiment. [Figure 4] FIG. 4 is a plan view illustrating an electro-optical element according to the third embodiment. [Diagram 5] FIG. 5 is a schematic plan view illustrating a light source module according to a fourth embodiment including the electro-optical element 100 according to the first embodiment shown in FIG. [Figure 6] FIG. 6 is a schematic plan view illustrating a light source module according to a fifth embodiment including the electro-optical element 200 according to the second embodiment shown in FIG. [Figure 7]FIG. 7 is a schematic plan view illustrating a light source module according to a sixth embodiment including the electro-optical element 300 according to the third embodiment shown in FIG. [Figure 8] FIG. 8 is a conceptual diagram for explaining an example of the XR glasses of the present invention. [Figure 9] FIG. 9 is a conceptual diagram showing how an image is directly projected onto the retina by light emitted from the light source module in the XR glasses shown in FIG. [Figure 10] Fig. 10(a) is a plan view of an optical multiplexing / splitting unit 52 and an optical waveguide connected thereto, which were used in the simulation of Experimental Example 1. Fig. 10(b) is a cross-sectional view taken along line AA' in Fig. 10(a). Fig. 10(c) is a cross-sectional view taken along line BB' in Fig. 10(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In order to solve the above problems and provide an electro-optical element capable of forming a light source module having a high ratio of the intensity of output light to the intensity of light incident from a light source to an optical waveguide, the inventors have conducted extensive research, focusing on an optical multiplexing and branching section that branches an optical modulation optical waveguide, which guides modulated light modulated by a Mach-Zehnder type optical modulator, from an optical waveguide for monitoring.

[0017] As a result, the inventors discovered that in an optical multiplexing / branching section of an electro-optical element, two optical waveguides for optical modulation, which guide modulated light modulated by a Mach-Zehnder type optical modulator, can be branched into three or more waveguides, with only one of them being a monitor optical waveguide and the others being optical output side optical waveguides, and thus arrived at the present invention. In an electro-optical element equipped with such an optical multiplexing / splitting section, only 1 / (the number of optical waveguides on the optical output side + 1) of the modulated light emitted from the electro-optical element is used as monitor light. Therefore, the amount of light used as monitor light is small, and the ratio of the intensity of the output light to the intensity of the light incident from the light source to the optical waveguide is high, allowing efficient use of the light emitted from the light source.

[0018] The present invention includes the following aspects. [1] A substrate; An optical function layer formed on a main surface of the substrate, The optical functional layer is a light incident side optical waveguide that guides light emitted from a light source; an optical branching unit that branches the light incident side optical waveguide into two optical modulation optical waveguides; a Mach-Zehnder type optical modulation unit that modulates light guided through two optical waveguides for optical modulation; an optical multiplexing / splitting section for splitting two optical modulation optical waveguides, which guide modulated light modulated by the Mach-Zehnder type optical modulation section, into one monitor optical waveguide and a plurality of optical output side optical waveguides; an optical multiplexing section that combines the plurality of optical output side optical waveguides into one optical output waveguide,

[0019] [2] The electro-optical element according to [1], wherein the light incident side optical waveguide, the light modulation optical waveguide, the monitor optical waveguide, the light output side optical waveguide, and the light output optical waveguide are all made of lithium niobate. [3] The electro-optical element according to [1], wherein the optical branching section, the optical multiplexing / branching section, and the optical multiplexing section are all multi-mode interferometers. [4] The electro-optical element according to [1], wherein the number of the optical output side optical waveguides is two.

[0020] [5] a photodetector for detecting a fluctuation in the amount of monitor light guided through the monitor optical waveguide; and a control unit that corrects the intensity of light guided through the optical waveguide for optical modulation in accordance with a detection result of the monitor light by the optical detector. [6] The optical function layer further comprises: an optical input port for inputting the light emitted from the light source into the light incident side optical waveguide; The electro-optical element according to [1], wherein the light incident side optical waveguide guides light input from the light input port.

[0021] [7] The optical functional layer further comprises: a bias electrode provided on each of the two optical waveguides for optical modulation arranged between the optical branching unit and the Mach-Zehnder type optical modulation unit; The electro-optical element according to [5], wherein the control unit controls a DC voltage applied from a bias electrode to the optical waveguide for optical modulation.

[0022] [8] The optical functional layer is the optical modulator includes three optical modulators each including the light incident side optical waveguide, the optical branching unit, the Mach-Zehnder type optical modulator, the optical multiplexing / branching unit, and the optical multiplexing unit; The electro-optical element according to [1], wherein the light incident side optical waveguides of each optical modulation section guide light having different wavelengths.

[0023] [9] A light source; A light source module comprising the electro-optical element according to any one of [1] to [8].

[10] A light source and the electro-optical element according to [5], The control unit controls a current supplied to the light source.

[0024]

[11] An optical engine comprising the light source module according to [9].

[12] XR glasses equipped with the light source module described in [9].

[0025] The electro-optical element, light source module, optical engine, and XR glasses of the present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand. Therefore, 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. They can be appropriately modified and implemented within the scope of the effects of the present invention.

[0026] [Electro-optical element] [First embodiment] 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'. The electro-optical element 100 shown in Fig. 1 includes a substrate 10 and an optical function layer 20 formed on a main surface 10a of the substrate 10, as shown in Fig. 2. The optical function layer 20 includes an optical waveguide core film 24 and an optical waveguide clad (buffer) film 25 formed on the optical waveguide core film 24 so as to cover the optical waveguide core film 24, as shown in Fig. 2.

[0027] As shown in FIG. 1, the optical functional layer 20 has an optical input port 2a, a light incident side optical waveguide 21, an optical branching section 51, optical modulation optical waveguides 21a, 21b, 21c, and 21d, a Mach-Zehnder type optical modulation section 40, an optical multiplexing and branching section 52, a monitor optical waveguide 3, a monitor optical output port 2c, optical output side optical waveguides 21e and 21f, an optical multiplexing section 53, an optical output optical waveguide 22, and an optical output port 2b.

[0028] The electro-optical element 100 of this embodiment has a generally rectangular shape in a plan view, and has four side surfaces, namely, a first side surface 100A and a third side surface 100C along the short sides of the rectangle, and a second side surface 100B and a fourth side surface 100D along the long sides, as shown in Fig. 1. In the electro-optical element 100 of this embodiment, an optical input port 2a is provided on the first side surface 100A, and an optical output port 2b is provided on the third side surface 100C. In addition, in the electro-optical element 100 of this embodiment, a monitor optical output port 2c is provided on the second side surface 100B.

[0029] In the electro-optical element 100 of this embodiment, the positions at which the light input port 2a, the light output port 2b, and the monitor light output port 2c are provided are not limited to the positions shown in Fig. 1. For example, in this embodiment, the monitor light output port 2c is provided on the second side surface 100B, but the monitor light output port 2c may be provided on any of the first side surface 100A, the third side surface 100C, and the fourth side surface 100D, and is not particularly limited. In addition, when the monitor light output port 2c is provided on the fourth side surface 100D, the monitor optical waveguide 3 may intersect with other optical waveguides, such as the optical output side optical waveguides 21e and 21f, in a plan view. Furthermore, the optical input port 2a, the optical output port 2b, and the monitor optical output port 2c may each be input / output to / from the top surface of the electro-optical element 100 using a structure such as a grating coupler or a mirror. In this case, the optical input port 2a, the optical output port 2b, and the monitor optical output port 2c do not need to be provided on the first side surface 100A, the third side surface 100C, and the fourth side surface 100D, and may be provided anywhere on the top surface of the electro-optical element 100.

[0030] In addition, in this embodiment, the electro-optical element 100 has been described as having a generally rectangular shape when viewed from above. However, the planar shape of the electro-optical element 100 is not limited to a generally rectangular shape, and may be any planar shape that can be appropriately determined depending on the application of the electro-optical element 100.

[0031] The light input port 2a, which inputs light emitted from a light source to the light incident side optical waveguide 21, is provided on the first side surface 100A. The light incident side optical waveguide 21 guides the light emitted from the light source and input from the light input port 2a. The optical branching unit 51 branches one light incident side optical waveguide 21 into two optical modulation optical waveguides 21a and 21b. A known optical branching unit can be used as the optical branching unit 51, and a multimode interferometer (MMI) is preferable.

[0032] The Mach-Zehnder type optical modulation section 40 modulates the light guided through the two optical waveguides 21a and 21b for optical modulation. The Mach-Zehnder type optical modulation section 40 may have a known configuration. As shown in FIG. 1, the Mach-Zehnder type optical modulation section 40 is provided with electrodes 26 and 27 for applying a modulation voltage to the Mach-Zehnder type optical modulation section 40. One end of the electrode 26 is connected to a power supply (not shown), and the other end is connected to a termination resistor 28. One end of the electrode 27 is connected to a power supply (not shown), and the other end is connected to the termination resistor 28. The electrodes 26 and 27 may be made of, for example, an Au film or a laminated film of a Ti film and an Au film.

[0033] The optical multiplexing / branching section 52 couples two optical modulation optical waveguides 21c, 21d that guide the modulated light modulated by the Mach-Zehnder type optical modulator 40, and branches the light into one monitor optical waveguide 3 and multiple optical output side optical waveguides 21e, 21f. The number of optical output side optical waveguides 21e, 21f is two, which is preferable because it allows the length of the optical multiplexing section 53 to be shortened.

[0034] In this embodiment, the case where there are two optical output side optical waveguides 21e, 21f will be described as an example, but the number of optical output side optical waveguides may be more than one, and may be three or more. When there are three or more optical output side optical waveguides, the amount of modulated light emitted from the electro-optical element 100 that is used as monitor light can be further reduced. The optical multiplexer / splitter 52 may be a known one, and is preferably a multimode interferometer (MMI).

[0035] The optical multiplexer 53 couples a plurality of (two in this embodiment) optical output side optical waveguides 21e, 21f to form one optical output optical waveguide 22. A known optical multiplexer 53 can be used, and a multimode interferometer (MMI) is preferable.

[0036] In this embodiment, it is preferable that at least one selected from the optical branching unit 51, the optical multiplexing / branching unit 52, and the optical multiplexing unit 53 is a multimode interferometer, and it is most preferable that all of them are multimode interferometers. The multimode interferometer (MMI) can prevent an increase in coupling length compared to, for example, a case where a directional coupler is provided instead of a multimode interferometer. Therefore, when at least one selected from the optical branching unit 51, the optical multiplexing / branching unit 52, and the optical multiplexing unit 53 is a multimode interferometer, it is possible to improve the degree of freedom in designing the electro-optical element 100 and to achieve miniaturization. In addition, when at least one selected from the optical branching unit 51, the optical multiplexing / branching unit 52, and the optical multiplexing unit 53 is a multimode interferometer, the loss of light due to manufacturing variations in the electro-optical element 100 is reduced.

[0037] The electro-optical element 100 of this embodiment preferably has a photodetector (not shown) that detects fluctuations in the amount of monitor light guided through the monitor optical waveguide 3, and a control unit (not shown) that corrects the intensity of light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation according to the detection result of the monitor light by the photodetector. As the light detector, for example, a known photodiode or the like can be used.

[0038] The control unit corrects the intensity of the light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation according to the detection result of the monitor light by the photodetector, and may, for example, control the current supplied to the light source (not shown) according to the detection result of the monitor light and / or control the DC (direct current) voltage supplied to the electrodes 26 and 27 that apply a modulation voltage to the Mach-Zehnder type optical modulation unit 40.

[0039] In this embodiment, the light incident side optical waveguide 21, the optical modulation optical waveguides 21a, 21b, 21c, and 21d, the monitor optical waveguide 3, the light output side optical waveguides 21e and 21f, and the light output optical waveguide 22 shown in Fig. 1 are all optical waveguides made of the optical waveguide core film 24 shown in Fig. 2. It is preferable that each of these optical waveguides has a ridge-like (convex) shape protruding from the first surface 24a of the optical waveguide core film 24 (see the cross-sectional shapes of the monitor optical waveguide 3 and the light output side optical waveguides 21e and 21f shown in Fig. 2). As shown in Fig. 2, the first surface 24a of the optical waveguide core film 24 is the upper surface of the portion (slab portion) other than the ridge shape of the optical waveguide core film 24.

[0040] The cross-sectional shapes of the light incident side optical waveguide 21, the optical modulation optical waveguides 21a, 21b, 21c, and 21d, the monitor optical waveguide 3, the light output side optical waveguides 21e and 21f, and the light output optical waveguide 22 shown in FIG. 1 may be any shape that can guide light, and is preferably a ridge-like shape, and may be, for example, a substantially rectangular, substantially trapezoidal, substantially triangular, or substantially semicircular shape.

[0041] When the cross-sectional shape of the optical waveguides (light incident side optical waveguide 21, optical modulation optical waveguides 21a, 21b, 21c, 21d, monitor optical waveguide 3, light output side optical waveguides 21e, 21f, light output optical waveguide 22) of the electro-optical element 100 of this embodiment is ridge-shaped, the width (Wa in FIG. 2) in the width direction (y direction) of the electro-optical element 100 in the cross-sectional shape of the optical waveguide can be, for example, 0.2 μm or more and 5.0 μm or less, and the height (protruding height Ha from the first surface 24a in FIG. 2) can be, for example, 0.1 μm or more and 1.0 μm or less.

[0042] The thickness of the optical waveguide core film 24 of the electro-optical element 100 of this embodiment can be, for example, 0.5 μm or more and 2 μm or less. The thickness of the optical waveguide core film 24 refers to the thickness of the portion (slab portion) of the optical waveguide core film 24 that is not in a ridge shape. The thickness of the optical waveguide core film 24 can be appropriately determined depending on the wavelength of the light guided through the optical waveguide, the cross-sectional shape of the optical waveguide of the electro-optical element 100, etc.

[0043] In the electro-optical element 100 shown in Fig. 1, the substrate 10 shown in Fig. 2 may be a known one, and may be appropriately determined according to the material of the optical function layer 20. When the optical waveguide core film 24 of the optical function layer 20, which is formed in contact with the main surface 10a of the substrate 10 and forms an optical waveguide, is an epitaxial film made of lithium niobate (LiNbO3), a known single crystal substrate capable of growing an epitaxial film made of lithium niobate (LiNbO3) is used as the substrate 10. In this case, the substrate 10 preferably has a lower refractive index than lithium niobate, and may be, for example, a sapphire single crystal substrate or a silicon single crystal substrate.

[0044] In the electro-optical element 100 of this embodiment, it is particularly preferable to use a sapphire single crystal substrate as the substrate 10. The sapphire single crystal substrate has a lower refractive index than a lithium niobate (LiNbO3) film. Therefore, when the optical waveguide core film 24 is an epitaxial film made of a lithium niobate film, the substrate 10 can play the role of a clad layer in the optical waveguide made of the optical waveguide core film 24. Therefore, when the substrate 10 is a sapphire single crystal substrate and the optical waveguide core film 24 is an epitaxial film made of a lithium niobate film, the optical waveguide core film 24 can be suitably used as an optical waveguide without providing a separate clad layer between the substrate 10 and the optical waveguide core film 24.

[0045] An epitaxial film made of lithium niobate (LiNbO3) is easily formed as a c-axis oriented epitaxial film on single crystal substrates of various crystal orientations. Therefore, in the electro-optical element 100 of this embodiment, when the optical waveguide core film 24 is made of a lithium niobate film, which is a c-axis oriented epitaxial film, the crystal orientation of the substrate 10 is not particularly limited.

[0046] Furthermore, when the optical waveguide core film 24 is made of a lithium niobate film, which is an epitaxial film oriented along the c-axis, it has three-fold symmetry. Therefore, it is desirable that the crystal orientation of the main surface 10a of the substrate 10 has the same symmetry as that of the optical waveguide core film 24. For this reason, when a sapphire single crystal substrate is used as the substrate 10, it is preferable that the main surface 10a is a c-plane. Furthermore, when a silicon single crystal substrate is used as the substrate 10, it is preferable that the main surface 10a is a (111) plane.

[0047] A known material can be used as the optical waveguide core film 24. It is preferable to use a lithium niobate film, which is a c-axis oriented epitaxial film, as the optical waveguide core film 24. The lithium niobate film forming the optical waveguide core film 24 is mainly composed of lithium niobate (LiNbO3). Lithium niobate has a large electro-optic constant and is therefore suitable as a material for optical waveguides.

[0048] The composition of the lithium niobate film forming the optical waveguide core film 24 is expressed, for example, by the general formula LixNbAyOz (wherein A is an element other than Li, Nb, and O, x is 0.5 to 1.2, y is 0 to 0.5, and z is 1.5 to 4). In the formula, A represents an element other than Li, Nb, and O. Examples of elements represented by 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. The element represented by A may be one type only, or two or more types. In the formula, x is an integer of 0.5 to 1.2, and preferably 0.9 to 1.05. In the formula, y is an integer of 0 to 0.5. In the formula, z is from 1.5 to 4, and preferably from 2.5 to 3.5.

[0049] When the optical waveguide core film 24 is made of a lithium niobate film that is an epitaxial film oriented along the c-axis, and the substrate 10 is made of a single crystal substrate, the crystal orientation of the lithium niobate film forming the optical waveguide core film 24 is aligned with the crystal orientation of the underlying substrate 10. More specifically, when the film plane of the lithium niobate film forming the optical waveguide core film 24 is taken as the XY plane and the film thickness direction is taken as the Z axis, the crystals of the single crystal substrate forming the substrate 10 and the crystals of the epitaxial film forming the optical waveguide core film 24 are aligned with the X-axis, Y-axis, and Z-axis directions.

[0050] The fact that the optical waveguide core film 24 is a c-axis oriented epitaxial film can be proven, for example, by first confirming the peak intensity at the orientation position by 2θ-θ X-ray diffraction, and secondly, by confirming the pole by pole measurement.

[0051] Specifically, in order to prove that the optical waveguide core film 24 is a c-axis oriented epitaxial film, the first condition is that when measured by 2θ-θ X-ray diffraction, all peak intensities other than the target plane must be 10% or less, preferably 5% or less, of the maximum peak intensity of the target plane. In the c-axis oriented epitaxial film forming the optical waveguide core film 24, the peak intensities other than the (00L) plane must be 10% or less, preferably 5% or less, of the maximum peak intensity of the (00L) plane. (00L) is a general designation for equivalent planes such as (001) and (002).

[0052] The above-mentioned conditions for checking the peak intensity at the orientation position by 2θ-θ X-ray diffraction only show the orientation in one direction. Therefore, even if the above-mentioned first condition is met, if the crystal orientation is not uniform within the plane, the intensity of the X-ray will not increase at a specific angle position and no pole will be observed. Therefore, in order to prove that the optical waveguide core film 24 is an epitaxial film oriented along the c-axis, the second condition is that the poles must be visible in the pole measurements.

[0053] Since LiNbO3 has a trigonal crystal structure, there are three poles of LiNbO3(014) in a single crystal. It is known that when a lithium niobate film is epitaxially grown, it grows epitaxially in a so-called twin state, in which crystals rotated 180° around the c-axis are symmetrically bonded. In this case, two of the three poles are symmetrically bonded, resulting in six poles.

[0054] In the electro-optical element 100 of this embodiment, when a sapphire single crystal substrate having a c-plane as the main surface 10a is used as the substrate 10, the c-axis of the lithium niobate film forming the optical waveguide core film 24 is preferably misaligned with the c-axis of the substrate 10 by 5° or less, and more preferably is coincident with that of the optical waveguide core film 24 (0°). If the c-axis misalignment between the optical waveguide core film 24 and the substrate 10 is 5° or less, there will be no practical problem in the characteristics of the electro-optical element 100 due to the misalignment between the c-axis of the optical waveguide core film 24 and the substrate 10.

[0055] In the electro-optical element 100 of this embodiment, a known material can be used as the optical waveguide clad (buffer) film 25 formed on the optical waveguide core film 24. As the clad (buffer) film 25, for example, a SiO2 film can be used.

[0056] The electro-optical element 100 of this embodiment includes an optical function layer 20 having an optical multiplexing / branching section 52 that branches two optical modulation optical waveguides 21c and 21d, which guide modulated light modulated by the Mach-Zehnder type optical modulator 40, into one monitor optical waveguide 3 and two optical output side optical waveguides 21e and 21f, and an optical multiplexing section 53 that combines the two optical output side optical waveguides 21e and 21f into one optical output optical waveguide 22. Therefore, in the electro-optical element 100 of this embodiment, only 1 / (the number of optical output side optical waveguides 21e and 21f (2)+1) of the amount of modulated light emitted from the electro-optical element 100 is used as monitor light. Therefore, the electro-optical element 100 of this embodiment can form a light source module in which a small amount of modulated light emitted from the electro-optical element 100 is used as monitor light, and the ratio of the intensity of the output light to the intensity of the light incident from the light source to the optical waveguide is high.

[0057] Moreover, the electro-optical element 100 of this embodiment has a photodetector (not shown) that detects fluctuations in the amount of monitor light guided through the monitor optical waveguide 3, and a control unit (not shown) that corrects the intensity of light guided through the optical modulation optical waveguides 21a, 21b, 21c, and 21d according to the detection result of the monitor light by the photodetector. In the electro-optical element 100 of this embodiment, the control unit can perform feedback control, for example, to control the current supplied to the light source (not shown) and / or to control the DC (direct current) voltage supplied to the electrodes 26 and 27 that apply a modulation voltage to the Mach-Zehnder type optical modulation unit 40 according to the detection result of the monitor light by the photodetector. Therefore, the electro-optical element 100 of this embodiment can emit stable modulated light in which fluctuations due to temperature and / or DC drift are suppressed.

[0058] [Second embodiment] Fig. 3 is a schematic plan view showing an electro-optical element according to a second embodiment. In an electro-optical element 200 according to the second embodiment shown in Fig. 3, components common to the electro-optical element 100 according to the first embodiment shown in Figs. 1 and 2 are denoted by the same reference numerals, and descriptions thereof may be omitted.

[0059] An electro-optical element 200 according to the second embodiment shown in Fig. 3 differs from the electro-optical element 100 according to the first embodiment shown in Fig. 1 and Fig. 2 in that DC (direct current) bias electrodes 31, 32 are provided on two optical modulation optical waveguides 21a, 21b arranged between an optical branching section 51 and a Mach-Zehnder type optical modulation section 40, respectively, and a control section controls the DC voltages applied from the bias electrodes 31, 32 to the optical modulation optical waveguides 21a, 21b. The bias electrodes 31, 32 may be made of, for example, an Au film or a laminated film of a Ti film and an Au film.

[0060] The control unit corrects the intensity of light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation according to the detection result of the monitor light by a photodetector (not shown) that detects the fluctuation in the amount of monitor light guided through the monitor optical waveguide 3, and controls the DC voltage applied from the bias electrodes 31 and 32 to the optical waveguides 21a and 21b for optical modulation. The control unit may control the current supplied to the light source (not shown) and / or control the DC (direct current) voltage supplied to the electrodes 26 and 27 that apply a modulation voltage to the Mach-Zehnder type optical modulator 40, and may also control the DC voltage applied from the DC (direct current) bias electrodes 31 and 32 to the optical waveguides 21a and 21b for optical modulation.

[0061] 1 and 2, in the electro-optical element 200 according to the second embodiment shown in Fig. 3, only 1 / (the number of optical output side optical waveguides 21e, 21f (2)+1) of the modulated light emitted from the electro-optical element 200 is used as monitor light. Therefore, in the electro-optical element 200 according to the second embodiment, only a small amount of the modulated light emitted from the electro-optical element 200 is used as monitor light, and a light source module can be formed in which the ratio of the intensity of the output light to the intensity of the light incident from the light source to the optical waveguide is high.

[0062] Moreover, the electro-optical element 200 according to the second embodiment shown in FIG. 3 has a photodetector (not shown) that detects fluctuations in the amount of monitor light guided through the monitor optical waveguide 3, and a control unit (not shown) that corrects the intensity of light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation in accordance with the detection result of the monitor light by the photodetector. DC (direct current) bias electrodes 31 and 32 are provided on the two optical waveguides 21a and 21b for optical modulation that are arranged between the optical branching unit 51 and the Mach-Zehnder type optical modulation unit 40, respectively.

[0063] 3, the control unit can perform feedback control to control the DC voltage applied from the DC (direct current) bias electrodes 31, 32 to the optical waveguides 21a, 21b for optical modulation in response to the detection result of the monitor light by the photodetector. Therefore, according to the electro-optical element 200 of this embodiment, the light guided through the optical waveguides 21a, 21b for optical modulation before reaching the Mach-Zehnder type optical modulator 40 is modulated, so that stable modulated light in which fluctuations due to temperature and / or DC drift are suppressed can be emitted.

[0064] 3, the control unit can perform feedback control to control the current supplied to the light source (not shown) and / or the DC (direct current) voltage supplied to the electrodes 26, 27 that apply a modulation voltage to the Mach-Zehnder type optical modulation unit 40, and to control the DC voltage applied from the DC (direct current) bias electrodes 31, 32 to the optical modulation optical waveguides 21a, 21b. This makes it possible to emit stable modulated light in which fluctuations due to temperature and / or DC drift are more effectively suppressed from the electro-optical element 200 of this embodiment.

[0065] [Third embodiment] Fig. 4 is a schematic plan view showing an electro-optical element according to a third embodiment. In an electro-optical element 300 according to the third embodiment shown in Fig. 4, the same members as those in the electro-optical element 100 according to the first embodiment shown in Figs. 1 and 2 are denoted by the same reference numerals, and descriptions thereof may be omitted. The electro-optical element 300 according to the third embodiment shown in FIG. 3 differs from the electro-optical element 100 according to the first embodiment shown in FIG. 1 and FIG. 2 in that the optical functional layer 20 has three optical modulation sections 20R, 20G, and 20B.

[0066] Each of the optical modulation sections 20R, 20G, and 20B of the electro-optical element 300 according to the third embodiment has an optical input port 2a, a light incident side optical waveguide 21, an optical branching section 51, optical modulation optical waveguides 21a, 21b, 21c, and 21d, a Mach-Zehnder type optical modulation section 40, an optical multiplexing and branching section 52, a monitor optical waveguide 3, a monitor optical output port 2c, optical output side optical waveguides 21e and 21f, an optical multiplexing section 53, an optical output optical waveguide 22, and an optical output port 2b.

[0067] The light incident side optical waveguide 21 of each of the optical modulation sections 20R, 20G, and 20B guides light of different wavelengths emitted from the respective light sources and input from the optical input port 2a. Specifically, the light incident side optical waveguide 21 of the optical modulation unit 20R guides, for example, red light having a peak wavelength of 610 nm or more and 750 nm or less. The light incident side optical waveguide 21 of the optical modulation unit 20G guides, for example, green light having a peak wavelength of 500 nm or more and 560 nm or less. The light incident side optical waveguide 21 of the optical modulation unit 20B guides, for example, blue light having a peak wavelength of 435 nm or more and 480 nm or less. When the light incident side optical waveguides 21 of the optical modulation sections 20R, 20G, and 20B in the electro-optical element 300 according to the third embodiment guide red light, green light, and blue light, respectively, the electro-optical element 300 can be preferably used, for example, in XR glasses capable of displaying full-color images.

[0068] In each of the optical modulation sections 20R, 20G, and 20B of the electro-optical element 300 of this embodiment, the positions at which the optical input port 2a, the optical output port 2b, and the monitor optical output port 2c are provided are not limited to the positions shown in FIG. 4. For example, in this embodiment, the monitor optical output port 2c is provided on the second side surface 100B in all of the optical modulation sections 20R, 20G, and 20B, but the monitor optical output port 2c in each of the optical modulation sections 20R, 20G, and 20B may be provided on any of the first side surface 100A, the third side surface 100C, and the fourth side surface 100D, and is not particularly limited. For example, only the monitor optical output port 2c in the optical modulation section 20G or only the monitor optical output port 2c in the optical modulation section 20B may be provided on the third side surface 100C or the fourth side surface 100D. Furthermore, the optical input port 2a, the optical output port 2b, and the monitor optical output port 2c may each be input / output to / from the top surface of the electro-optical element 300 using a structure such as a grating coupler or a mirror. In this case, the optical input port 2a, the optical output port 2b, and the monitor optical output port 2c do not need to be provided on the first side surface 100A, the third side surface 100C, and the fourth side surface 100D, and may be provided anywhere on the top surface of the electro-optical element 300.

[0069] Furthermore, the monitor optical waveguide 3 in each of the optical modulation sections 20R, 20G, and 20B of the electro-optical element 300 may intersect with optical waveguides of other optical modulation sections in a planar view (see, for example, the monitor optical waveguides 3 of the optical modulation sections 20G and 20B in FIG. 4).

[0070] In each of the optical modulation sections 20R, 20G, and 20B of the electro-optical element 300 of this embodiment, the electrodes 26 and 27 that apply a modulation voltage to the Mach-Zehnder type optical modulation section 40 have one end connected to a power supply (not shown) and the other end connected to a termination resistor (not shown).

[0071] In the electro-optical element 300 according to the third embodiment shown in Fig. 4, like the electro-optical element 100 according to the first embodiment shown in Fig. 1 and Fig. 2, only 1 / (the number of optical output side optical waveguides 21e, 21f (2)+1) of the modulated light output from each of the optical modulation sections 20R, 20G, 20B is used as monitor light. Therefore, in the electro-optical element 300 according to the third embodiment, the optical modulation sections 20R, 20G, 20B use only a small amount of modulated light output from each of the optical modulation sections 20R, 20G, 20B as monitor light, and the ratio of the intensity of the output light to the intensity of the light input from the light source to the optical waveguide is high.

[0072] [Other examples] The electro-optical element of the present invention is not limited to the electro-optical elements of the first to third embodiments described above, and can be modified as appropriate within the scope of the invention. For example, each of the optical modulation sections 20R, 20G, and 20B of the electro-optical element 300 according to the third embodiment shown in FIG. 4 may have DC (direct current) bias electrodes 31 and 32 provided on two optical waveguides for optical modulation 21a and 21b arranged between the optical branching section 51 and the Mach-Zehnder type optical modulation section 40, respectively, similar to the electro-optical element 200 according to the second embodiment shown in FIG. 3, and the DC voltage applied from the bias electrodes 31 and 32 to the optical waveguides for optical modulation 21a and 21b may be controlled by a control section.

[0073] [Light source module] [Fourth embodiment] Fig. 5 is a schematic plan view illustrating a light source module according to a fourth embodiment including the electro-optical element 100 according to the first embodiment shown in Fig. 1. The light source module 400 of this embodiment includes the electro-optical element 100 of the first embodiment and a light source 30. 5, the light source 30 emits light that is incident from the light input port 2a of the electro-optical element 100 and is guided through the light incident side optical waveguide 21. As the light source 30, a laser element such as a laser diode (LD) can be used, and various commercially available laser elements that emit light of a specific wavelength such as red light, green light, or blue light can be used.

[0074] In the light source module 400 of this embodiment, it is preferable that the current supplied to the light source 30 is controlled by the control unit of the electro-optical element 100 in accordance with the detection result of the fluctuation in the amount of monitor light guided through the monitor optical waveguide 3 of the electro-optical element 100. In this case, by controlling the current supplied to the light source 30, the amount of light emitted from the light source 30 can be adjusted, and even if the modulated light fluctuates due to temperature and / or DC drift amount, the intensity (light amount) of the light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation can be corrected in accordance with the amount of the fluctuation.

[0075] Furthermore, since the light source module 400 of this embodiment includes the electro-optical element 100 of the first embodiment and the light source 30, the amount of light used as monitor light is small, and the ratio of the intensity of the output light to the intensity of the light incident from the light source 30 through the light input port 2 a into the light incident side optical waveguide 21 is high.

[0076] [Fifth embodiment] Fig. 6 is a schematic plan view illustrating a light source module according to a fifth embodiment including the electro-optical element 200 according to the second embodiment shown in Fig. 3. The light source module 500 of this embodiment includes the electro-optical element 200 of the second embodiment and a light source 30. 6, like the electro-optical element 100 of the light source module 400 shown in Fig. 5, emits light that is incident from the light input port 2a and guided through the light incident side optical waveguide 21. As the light source 30, a light source similar to the light source 30 of the light source module 400 can be used.

[0077] In the light source module 500 of this embodiment, it is preferable that the current supplied to the light source 30 is controlled by the control unit of the electro-optical element 200 in accordance with the detection result of the fluctuation in the amount of monitor light guided through the monitor optical waveguide 3 of the electro-optical element 200. In this case, by controlling the current supplied to the light source 30, the amount of light emitted from the light source 30 can be adjusted, and even if the modulated light fluctuates due to temperature and / or DC drift amount, the intensity (light amount) of the light guided through the optical waveguides 21a, 21b, 21c, and 21d for optical modulation can be corrected in accordance with the amount of the fluctuation.

[0078] Furthermore, since the light source module 500 of this embodiment includes the electro-optical element 200 of the second embodiment and the light source 30, the amount of light used as monitor light is small, and the ratio of the intensity of the output light to the intensity of the light incident from the light source 30 through the light input port 2 a into the light incident side optical waveguide 21 is high.

[0079] [Sixth embodiment] Fig. 7 is a schematic plan view for explaining a light source module according to a sixth embodiment including the electro-optical element 300 according to the third embodiment shown in Fig. 4. The light source module 600 of this embodiment includes the electro-optical element 300 of the third embodiment and three light sources 30R, 30G, and 30B. As shown in FIG. 7, three light sources 30R, 30G, and 30B emit light that is incident from the light input ports 2a of the optical modulation sections 20R, 20G, and 20B of the electro-optic element 300 and guided through the light incident side optical waveguide .

[0080] The light sources 30R, 30G, and 30B may be laser elements such as laser diodes (LDs). The light source 30R may be, for example, any of various commercially available laser elements that emit red light with a peak wavelength of 610 nm or more and 750 nm or less. The light source 30G may be, for example, any of various commercially available laser elements that emit green light with a peak wavelength of 500 nm or more and 560 nm or less. The light source 30B may be, for example, any of various commercially available laser elements that emit blue light with a peak wavelength of 435 nm or more and 480 nm or less.

[0081] In the light source module 600 of this embodiment, it is preferable that the control unit of the electro-optical element 300 controls the currents supplied to the three light sources 30R, 30G, and 30B according to the detection result of the light amount fluctuation of the monitor light guided through the monitor optical waveguide 3 provided in each optical modulation unit 20R, 20G, and 20B of the electro-optical element 300. In this case, by controlling the currents supplied to the three light sources 30R, 30G, and 30B, the light amounts emitted from the three light sources 30R, 30G, and 30B can be adjusted. Therefore, even if the modulated light fluctuates due to the temperature and / or DC drift amount in each optical modulation unit 20R, 20G, and 20B, the intensity of the light guided through the optical modulation optical waveguides 21a, 21b, 21c, and 21d can be corrected according to the amount of the fluctuation.

[0082] Furthermore, since the light source module 600 of this embodiment includes the electro-optical element 300 of the third embodiment and the light sources 30R, 30G, and 30B, the amount of light used as monitor light is small, and the ratio of the intensity of the output light to the intensity of the light incident from the light sources 30R, 30G, and 30B to the light incident side optical waveguide 21 via the light input port 2a is high.

[0083] [Optical engine and XR glasses] Fig. 8 is a conceptual diagram for explaining an example of the XR glasses of the present invention. Fig. 9 is a conceptual diagram showing how an image is directly projected onto the retina by the laser light emitted from the light source module in the XR glasses shown in Fig. 8.

[0084] The XR glasses (eyeglasses) 1000 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. 9 is image display light.

[0085] The XR glasses 1000 of this embodiment shown in FIG. 8 are configured such that the light source module 1001 according to the above-described embodiment is mounted on an optical engine 5001 disposed on a frame 1010. As shown in FIG. 8, the optical engine 5001 includes a light source module 1001, an optical scanning mirror 3001, an optical system 2001 connecting the light source module 1001 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.

[0086] 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 a two-axis MEMS mirror as the optical scanning mirror 3001, which vibrates to reflect laser light by changing the angle in the horizontal direction (X direction) and the vertical direction (Y direction).

[0087] The optical system 2001 optically processes the laser light emitted from the light source module 1001. For example, the optical system 2001 may include a collimator lens 2001a, a slit 2001b, and an ND filter 2001c. The optical system 2001 shown in FIG. 8 is an example, and other configurations may be used.

[0088] In the XR glasses 1000 of this embodiment shown in Figure 8, as shown in Figure 9, laser light R irradiated from a light source module 1001 attached to a frame 1010 is reflected by a light scanning mirror 3001 and further reflected by the lens of the XR glasses 1000, enters the person's eyeball E as image display light L, and an image (video) can be directly projected onto the retina M.

[0089] The XR glasses 1000 of this embodiment are equipped with the light source module 1001 of this embodiment, and therefore can efficiently utilize the light emitted from the light source.

[0090] 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 merely an example, and addition, omission, substitution, and other modifications of the configuration are possible without departing from the spirit of the present invention. EXAMPLES

[0091] The present invention will be described in more detail below using examples, but the present invention is not limited to the examples shown below.

[0092] (Experimental Example 1) A simulation was performed under the following conditions for the optical multiplexing / splitting section 52 provided in the electro-optical element according to the first to third embodiments shown in Figures 1 to 3. Fimmwave (Photon Design) was used as the simulation software.

[0093] Fig. 10(a) is a plan view of an optical multiplexing / splitting unit 52 and an optical waveguide connected thereto, which were used in the simulation of Experimental Example 1. Fig. 10(b) is a cross-sectional view taken along line AA' in Fig. 10(a). Fig. 10(c) is a cross-sectional view taken along line BB' in Fig. 10(a). 10(a) to 10(c), members corresponding to those included in the electro-optical element shown in FIGS. 1 to 3 are denoted by the same reference numerals as in FIGS. 1 to 3. In FIGS.

[0094] In the simulation of Experimental Example 1, the optical modulation optical waveguides 21c and 21d, the monitor optical waveguide 3, and the optical output side optical waveguides 21e and 21f shown in Fig. 10(a) to Fig. 10(c) were all assumed to have the same cross-sectional shape. Specifically, they were made of an optical waveguide core film 24 having a ridge-like shape, and had a trapezoidal cross-sectional shape with an upper base width of 2 μm, a height of 0.7 μm, and a side inclination angle of 80°. In addition, the film thickness of the optical waveguide core film 24 (the film thickness of the portion (slab portion) that is not ridge-like) was set to 0.15 μm. In addition, the distance between the centers of the lower bases of the two optical modulation optical waveguides 21c and 21d, the distance between the centers of the lower bases of the two optical output side optical waveguides 21e and 21f, and the distance between the centers of the lower bases of the monitor optical waveguide 3 and the optical output side optical waveguide 21e were all set to 4 μm.

[0095] The cross-sectional shape of the optical multiplexing / splitting section 52 was a trapezoid with a height of 0.7 μm and a side inclination angle of 80°. The lengths L_MMI and L_MMI_2 of the optical multiplexing / splitting section 52 shown in Figures 10(a) and 10(c) were set to the dimensions shown in Table 1 according to the wavelength of the input light, and the width of the upper base of the region with length L_MMI was set to 8 μm, and the width of the upper base of the region with length L_MMI_2 was set to 12 μm.

[0096] The substrate 10, the optical waveguide core film 24, and the optical waveguide cladding (buffer) film 25 shown in FIGS. 10(a) to 10(c) were made of the materials shown below. [material] Substrate 10; sapphire single crystal substrate Optical waveguide core film 24: Epitaxial film made of lithium niobate (LiNbO3) film Optical waveguide cladding (buffer) film 25; SiO2 film

[0097] In the simulation of experimental example 1, as shown in Table 1, three types of input light were used: red light of 637 nm, green light of 520 nm, and blue light of 455 nm, and the ratio of the output light intensity to the input light intensity of the optical multiplexing and branching section 52 (output light intensity / input light intensity) and the ratio of the monitor light intensity to the input light intensity (monitor light intensity / input light intensity) were calculated.

[0098] The input light intensity is the sum of the intensities of the lights incident from the optical modulation optical waveguides 21c and 21d shown in Fig. 10(a) to the optical multiplexing and branching unit 52. The output light intensity is the sum of the intensities of the lights output from the optical multiplexing and branching unit 52 shown in Fig. 10(a) to the optical output side optical waveguides 21e and 21f. The monitor light intensity is the intensity of the light output from the optical multiplexing and branching unit 52 shown in Fig. 10(a) to the monitor optical waveguide 3.

[0099] [Table 1]

[0100] As shown in Table 1, it has been confirmed that, regardless of whether the input light is red light of 637 nm, green light of 520 nm, or blue light of 455 nm, the optical multiplexing and branching section 52 that branches the two optical modulation optical waveguides 21c and 21d into one monitor optical waveguide 3 and two optical output side optical waveguides 21e and 21f has a high ratio of output light intensity to input light intensity of the optical multiplexing and branching section 52, which is about 2 / 3, and a low ratio of monitor light intensity to input light intensity, which is about 1 / 3. [Explanation of symbols]

[0101] 2a optical input port, 2b optical output port, 2c monitor optical output port, 3 monitor optical waveguide, 10 substrate, 10a main surface, 20 optical function layer, 20R, 20G, 20B optical modulation section, 21 light input side optical waveguide, 21a, 21b, 21c, 21d optical modulation optical waveguide, 21e, 21f optical output side optical waveguide, 22 optical output optical waveguide, 24 optical waveguide core film, 25 optical waveguide clad (buffer) film, 26, 27 electrode, 28 termination resistor, 30, 30R, 30G, 30B light source, 31, 32 bias electrode, 40 Mach-Zehnder type optical modulation section, 51 optical branching section, 52 optical multiplexing / branching section, 53 optical multiplexing section, 100, 200, 300 Electro-optical element, 100A first side, 100B second side, 100C third side, 100D fourth side, 400, 500, 600, 1001 light source module, 1000 XR glasses (eyeglasses), 1010 frame, 1100 laser driver, 1200 optical scanning mirror driver, 1300 video controller, 2001 optical system, 2001a collimator lens, 2001b slit, 2001c ND filter, 3001 optical scanning mirror, 5001 optical engine.

Claims

1. A substrate; An optical function layer formed on a main surface of the substrate, The optical functional layer is a light incident side optical waveguide that guides light emitted from a light source; an optical branching unit that branches the light incident side optical waveguide into two optical modulation optical waveguides; a Mach-Zehnder type optical modulation unit that modulates light guided through two optical waveguides for optical modulation; an optical multiplexing / splitting section for splitting two optical modulation optical waveguides, which guide modulated light modulated by the Mach-Zehnder type optical modulation section, into one monitor optical waveguide and a plurality of optical output side optical waveguides; an optical multiplexing section that combines the plurality of optical output side optical waveguides into one optical output waveguide.

2. 2. The electro-optical element according to claim 1, wherein the light incident side optical waveguide, the light modulation optical waveguide, the monitor optical waveguide, the light output side optical waveguide, and the light output optical waveguide are all made of lithium niobate.

3. 2. The electro-optic element according to claim 1, wherein the optical branching section, the optical multiplexing / branching section, and the optical multiplexing section are all multimode interferometers.

4. 2. The electro-optical element according to claim 1, wherein the number of said plurality of optical output side optical waveguides is two.

5. a photodetector for detecting a fluctuation in the amount of monitor light propagating through the monitor optical waveguide; 2. The electro-optical element according to claim 1, further comprising: a control unit that corrects an intensity of light guided through said optical waveguide for optical modulation in accordance with a detection result of said monitor light by said photodetector.

6. The optical function layer further comprises: an optical input port for inputting the light emitted from the light source into the light incident side optical waveguide; The electro-optical element according to claim 1 , wherein the light incident side optical waveguide guides light input from the light input port.

7. The optical function layer further comprises: a bias electrode provided on each of the two optical waveguides for optical modulation arranged between the optical branching unit and the Mach-Zehnder type optical modulation unit; The electro-optical element according to claim 5 , wherein the control section controls a DC voltage applied from a bias electrode to the optical waveguide for optical modulation.

8. The optical functional layer is the optical modulator includes three optical modulators each including the light incident side optical waveguide, the optical branching unit, the Mach-Zehnder type optical modulator, the optical multiplexing / branching unit, and the optical multiplexing unit; 2. The electro-optic element according to claim 1, wherein the light incident side optical waveguides of the optical modulation sections guide light having different wavelengths.

9. A light source; A light source module comprising: the electro-optical element according to any one of claims 1 to 8.

10. A light source; The electro-optical element according to claim 5 , The control unit controls a current supplied to the light source.

11. An optical engine comprising the light source module according to claim 9 .

12. XR glasses equipped with the light source module according to claim 9.

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