Optical modulator, light source module, optical engine, and XR glasses

Abstract

The invention provides a visible light modulator which is small in size and capable of high-speed driving at low voltage. An optical modulator (1) is provided with: a substrate (2); an optical waveguide layer (3) comprising lithium niobate in which a plurality of MZ-type waveguides including first and second ridge waveguides that propagate visible light are arranged in parallel; a signal electrode having an interaction portion disposed along the MZ-type waveguide; the optical modulator includes a first ridge waveguide, a second ridge waveguide, a signal electrode disposed above the first ridge waveguide, a first ground electrode disposed above the second ridge waveguide, and signal electrode lead-out portions (62R-3, 62B-3, 62G-3) connecting the signal electrode and a pad disposed at an end edge portion (S3), and a second ground electrode disposed above the first ridge waveguide and the second ridge waveguide, the signal electrode lead-out portions (62R-3, 62B-3, 62G-3) connecting the signal electrode and the pad disposed at the end edge portion (S3). And a light multiplexing unit (40) that is disposed downstream of the Mach-Zehnder waveguide and multiplexes the plurality of visible light, in which the first ground electrode, the second ground electrode, and the signal electrode lead-out unit are disposed at positions that do not overlap the light multiplexing unit in plan view.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical modulator, a light source module, an optical engine, and an XR glass. BACKGROUND

[0002] In recent years, a light source module having an optical modulator that modulates incident light from a laser diode (semiconductor laser) has been attracting attention. Such a light source module can be used for an optical engine of a terminal of a glass type such as an XR glass such as an AR (Augmented Reality) glass, a VR (Virtual Reality) glass, and the like, a small-sized projector, and the like.

[0003] For example, in Patent Literature 1, an image display device is described, which includes a light source section that emits first light and second light, an optical modulator that has a modulation section of a Mach-Zehnder type modulation system, and an optical scanner that spatially scans the first light and the second light modulated by the optical modulator. In addition, in Patent Literature 1, as the image display device, a head-mounted display that is worn on the head of a user is described.

[0004] In addition, although not an image display device, in Patent Literature 2, a transmission device is described, which includes a laser light source that emits visible light and an optical modulator that generates a visible light signal by changing the intensity of the visible light. In Patent Literature 2, a Mach-Zehnder type optical modulator is described, which has a substrate, an optical waveguide layer, a buffer layer, and an electrode layer, and the optical waveguide layer is composed of a lithium niobate film. In addition, in Patent Literature 2, as the electrode layer of the optical modulator, an electrode layer having a first signal electrode, a second signal electrode, a first ground electrode, a second ground electrode, and a third ground electrode is disclosed. The optical modulator disclosed in Patent Literature 2 is a so-called dual-drive type optical modulator having two signal electrodes.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent No. 6728596

[0008] Patent Literature 2: Japanese Patent Application Publication No. 2022-036928 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] A preferred method disclosed in Patent Literature 1 is a method of using a single crystal or a solid solution crystal of lithium niobate, and modifying a part of the same by a proton exchange method or a Ti diffusion method as an optical waveguide. However, the size of the waveguide portion (core) region after modification is determined by the distance of the invasion / diffusion of protons or Ti, so it is difficult to reduce the diameter of the optical waveguide. Therefore, the optical waveguide itself becomes large, and in addition, since the diameter of the optical waveguide is large, it is difficult to concentrate the electric field of the modulation voltage, a large voltage needs to be applied for modulation, or in order to operate at a small voltage, the electrode to which the voltage is applied needs to be elongated, so the size of the element becomes large.

[0011] In order to popularize the eyeglass-type image display device such as the XR glasses, miniaturization and low driving voltage are required. In addition, in order to realize mass production thereof, it is required to be able to be manufactured at as low a cost as possible.

[0012] In the eyeglass-type image display device such as the XR glasses, a laser beam (LB) is scanned pixel by pixel in order to form one image. For example, in order to obtain a pixel resolution of 2560 x 1460, a high-speed modulation of about 1 GHz is required. Furthermore, 4K is 3840 x 2160, and a high-speed drive of 1 GHz or more is required.

[0013] The present application was made in view of the above technical problems, and an object thereof is to provide a visible light optical modulator which is small and capable of high-speed driving at a low voltage, an optical source module, an optical engine loaded with the optical source module, and an XR glasses.

[0014] Technical solution for solving the technical problem

[0015] The present application provides the following technical solution in order to solve the above technical problems.

[0016] Embodiment 1 of the present invention is an optical modulator comprising: a substrate; an optical waveguide layer made of lithium niobate formed on the substrate, wherein a plurality of Mach-Zehnder waveguides are arranged in parallel, the Mach-Zehnder waveguides including a first ridge waveguide and a second ridge waveguide for transmitting visible light; a buffer layer formed on the optical waveguide layer; a plurality of signal electrodes formed on the buffer layer and having interaction portions disposed along the plurality of Mach-Zehnder waveguides respectively; and a plurality of first ground electrodes and a plurality of second ground electrodes disposed separately from the signal electrodes on both sides of each of the plurality of signal electrodes; wherein the signal electrodes are disposed on the first ridge waveguides. Above, the second ground electrode is disposed above the second ridge waveguide. The optical modulator further includes: a signal electrode lead-out portion that connects the signal electrode to a pad disposed on the end edge of the substrate; a light-combining wave section disposed on the downstream side of the plurality of Mach-Zehnder waveguides, which combines multiple visible light waves passing through the plurality of Mach-Zehnder waveguides; a plurality of connecting waveguides that connect the downstream side of each of the plurality of Mach-Zehnder waveguides to the light-combining wave section; and an output waveguide connected to the light-combining wave section, wherein the first ground electrode, the second ground electrode, and the signal electrode lead-out portion are disposed at a position that does not overlap with the light-combining wave section when viewed from above.

[0017] In the second embodiment of the present invention, in the optical modulator of embodiment 1, there are three or more Mach-Zehnder waveguides and three or more signal electrodes. The three or more interaction portions of each of the multiple signal electrodes are arranged parallel to each other in a top view and sequentially arranged from the shortest side. The optical combining wave section is located downstream of the signal electrode with the shortest interaction portion among the multiple signal electrodes. There are three or more signal electrode leads. Two or more of the signal electrode leads extend from the downstream end of the interaction portion in a direction that does not intersect each other in a direction less than 90° relative to the direction of extension of the interaction portion, cross the multiple connecting waveguides in a top view, and are connected to a pad located at the downstream end edge of the signal electrode with the longest interaction portion.

[0018] In the third aspect of the present invention, in the optical modulator of either aspect 1 or aspect 2, a higher-order mode removal section configured to remove higher-order modes is provided on the waveguide upstream of each of the plurality of Mach-Zehnder waveguides before branching toward the first ridge waveguide and the second ridge waveguide.

[0019] The fourth embodiment of the present invention is a light source module, comprising: an optical modulator of any one of embodiments 1 to 3; and a plurality of light sources connected to the plurality of Mach-Zehnder waveguides, and emitting visible light that is incident on the plurality of input waveguides respectively.

[0020] The fifth aspect of the present invention is an optical engine comprising: a light source module of the fourth aspect; and a light scanning mirror that reflects light emitted from the light source module at a changing angle to display an image.

[0021] The sixth aspect of the present invention is an XR pair of glasses, wherein the optical engine of the fifth aspect is mounted.

[0022] Invention Effects

[0023] According to the optical modulator of the present invention, a small visible light optical modulator capable of high-speed driving at low voltage can be provided. Attached Figure Description

[0024] Figure 1 This is a plan view illustrating an example of an optical modulator in one embodiment.

[0025] Figure 2 It means to Figure 1 The diagram shown is an enlarged view of the area enclosed by three dashed boxes, and an enlarged view of one of the three enlarged views.

[0026] Figure 3 The optical modulator of this embodiment is along Figure 2 The diagram shows a cross-section cut by line AA′.

[0027] Figure 4 It is Figure 1 An enlarged view of the area enclosed by two dashed boxes in the plan view shown.

[0028] Figure 5 It is Figure 1 An enlarged view of the area enclosed by two dashed boxes in the plan view shown.

[0029] Figure 6 This diagram illustrates an example of adjusting the interaction lengths LR, LB, and LG of each visible light source to make Vπ less than 2V.

[0030] Figure 7 Indicates in Figure 6 The structure shown is a variation in which the positions of the Mach-Zehnder waveguide for blue light and the Mach-Zehnder waveguide for green light are swapped.

[0031] Figure 8A This is a diagram used to illustrate how multiple visible light beams combine.

[0032] Figure 8B It's magnified. Figure 8A A planar schematic diagram of the vicinity of the optically synthesized wave section 40, indicated by arrow B.

[0033] Figure 8C It's magnified. Figure 8A A planar schematic diagram of the vicinity of the optically synthesized wave section 40, indicated by arrow B.

[0034] Figure 9 This is a magnified planar schematic diagram of the vicinity of the high-order mode removal section of the optical modulator in this embodiment.

[0035] Figure 10 This is a plan view of a light source module according to one embodiment of the present invention.

[0036] Figure 11 It is cut by XZ plane Figure 10 The schematic diagram shown is a cross-sectional view of a portion of the light source module, depicting only a part near the joint.

[0037] Figure 12 This is a conceptual diagram illustrating an example of the XR glasses of the present invention.

[0038] Figure 13 It means in Figure 12 The diagram shows a concept of XR glasses in which an image is projected directly onto the retina using a laser emitted from a light source module. Detailed Implementation

[0039] Hereinafter, embodiments will be described in detail with appropriate reference to the accompanying drawings. In the drawings used in the following description, for ease of understanding and convenience, some features are sometimes shown as enlarged portions, and the dimensional ratios of the constituent elements may sometimes differ from the actual dimensions. The materials, dimensions, etc., illustrated in the following description are examples, and the present invention is not limited to these; appropriate modifications can be made to achieve the effects of the present invention.

[0040] [Optical modulator]

[0041] Figure 1 This is a plan view illustrating an example of an optical modulator according to one embodiment of the present invention. Figure 2 It is Figure 1 The diagram shows enlarged views of three parts of the plan view, and an enlarged view of one of those enlarged views. According to... Figure 2 The enlarged image, in Figure 1 In the planar schematic, lines that could not be decomposed are decomposed, and the shapes become clearer. Figure 1 and Figure 2 The optical waveguide structure is illustrated in the diagram, showing the arrangement of the optical waveguide structure and the electrode structure formed in the optical waveguide layer 3. Figure 3 It is along Figure 2 The diagram shows a cross-section cut by line AA′. Figure 4 It is Figure 1An enlarged view of the area enclosed by two dashed boxes in the plan view shown. Figure 5 It is Figure 1 An enlarged view of the area enclosed by two dashed boxes in the plan view shown.

[0042] exist Figures 1-5 In the diagram, the X direction is orthogonal to the side with the light entrance, the Y direction is orthogonal to the X direction, and the Z direction is orthogonal to the surface formed by the X and Y directions.

[0043] The optical modulator of this embodiment includes: multiple Mach-Zehnder type (MZI type) optical modulation units; and an optical combining unit for combining multiple visible lights modulated by these multiple Mach-Zehnder type optical modulation units. Hereinafter, the case where the multiple visible lights are red light (R), green light (G), and blue light (B) will be used as an example for explanation.

[0044] Figures 1-5 The optical modulator 1 shown includes: a substrate 2; an optical waveguide layer 3 made of lithium niobate formed on the substrate 2, wherein three Mach-Zehnder waveguides 32 (32R, 32B, 32G) comprising a first ridge waveguide 32c and a second ridge waveguide 32b for transmitting visible light are arranged in parallel; a buffer layer 52 formed on the optical waveguide layer 3; a plurality of signal electrodes 62 (62R, 62B, 62G) formed on the buffer layer 52, and having interaction portions 62R-2, 62G-2, and 62B-2 respectively arranged along the plurality of Mach-Zehnder waveguides; and a plurality of first ground electrodes 61A and a plurality of second ground electrodes 61B, which are disposed separately from the signal electrodes 62 (62R, 62B, 62G) on both sides of each of the plurality of signal electrodes 62 (62R, 62B, 62G). As shown in the figure, it can also be structured as follows: a first ground electrode and a second ground electrode associated with a signal electrode become the second ground electrode and the first ground electrode associated with adjacent signal electrodes, respectively.

[0045] Signal electrodes 62 (62R, 62B, 62G) are positioned above the first ridge waveguide 32b, and the second ground electrode 61B is positioned above the second ridge waveguide 32c.

[0046] Figure 1 The substrate 2 and the optical modulator 1 shown are rectangular in top view (viewed from the Z direction). For ease of explanation, regarding the four sides of this rectangle, the side where visible light is incident is designated as S1, the side opposite to S1 is designated as S2, the side orthogonal to S1 and S2 with a waveguide (which waves the longest wavelength visible light) is designated as S3, and the side opposite to S3 is designated as S4. Hereinafter, the portions near sides S1, S2, S3, and S4 will be referred to, for example, as end portions S3 and S4.

[0047] The optical modulator 1 includes signal electrode leads 62R-1, 62B-1, 62G-1, 62R-3, 62B-3, and 62G-3 that connect signal electrodes 62 (62R, 62B, 62G) to pads 63 (63R, 63B, 63G) and 64 (64R, 64G, 64B) respectively disposed on the end portions S4 and S3 of the substrate 2.

[0048] Additionally, the optical modulator 1 includes: an optical combining section 40 disposed on the downstream side (the side through which light propagates) of a plurality of Mach-Zehnder waveguides 32 (32R, 32B, 32G) to combine multiple visible light rays that have passed through the plurality of Mach-Zehnder waveguides 32 (32R, 32B, 32G); a plurality of connecting waveguides 32d (32Rd, 32Bd, 32Gd) that connect the downstream side of each of the plurality of Mach-Zehnder waveguides 32 (32R, 32B, 32G) to the optical combining section 40; and an output waveguide 32e connected to the optical combining section 40.

[0049] In the optical modulator 1, the first ground electrode 61A, the second ground electrode 61B, and the signal electrode leads 62R-3, 62B-3, and 62G-3 are positioned so as not to overlap with the optical wave combination section 40 when viewed from above.

[0050] In the light modulator 1, light of various colors generated from red (R), blue (B), and green (G) light sources enters through light inlets 32Rin, 32Bin, and 32Gin (see reference). Figure 2 The light is incident, and each color of light is modulated by the received light. In the light combining section 40, the three colors of light are combined, and the combined light exits from the light exit port 32 (see reference). Figure 2 () Launch.

[0051] Figures 1-5 The optical modulator 1 shown represents the case where there are three Mach-Zehnder waveguides 32, but it is not limited to three; multiple waveguides are acceptable.

[0052] (Positional relationship between the first grounding electrode, the second grounding electrode, the signal electrode lead-out section, and the optical wave section)

[0053] The optical modulator of this embodiment is configured such that the first ground electrode, the second ground electrode, and the signal electrode lead-out portion are positioned so as not to overlap with the optical wave section when viewed from above. Hereinafter, this example will be described based on the accompanying drawings, but this structure is not limited to this example.

[0054] In optical modulator 1, the three signal electrodes 62R, 62B, and 62G are arranged in the following order from the shortest (LG < LB < LR (refer to...)). Figure 6The three signal electrodes 62R, 62B, and 62G are arranged side by side, and their respective interaction parts 62R-2, 62B-2, and 62G-2 are parallel to each other when viewed from above. In other words, the three signal electrodes 62R, 62B, and 62G are arranged as follows: signal electrode 62B is arranged next to signal electrode 62G, and signal electrode 62R is arranged next to signal electrode 62B.

[0055] like Figure 4 As shown in the enlarged diagram, the pads 63R, 63B, and 63G for the three signal electrode leads 62R-1, 62B-1, and 62G-1 disposed on the end edge S4 of substrate 2 are arranged sequentially from the upstream side (the side where light is incident) to the downstream side (the side where light propagates) (+x direction). The signal electrode leads 62R-1, 62B-1, and 62G-1 extend from the three pads 63R, 63B, and 63G in a direction approximately orthogonal to the direction (x direction) extending from the interaction portions 62R-2, 62B-2, and 62G-2. The positions (coordinates) of the upstream ends 62R-2s, 62B-2s, and 62G-2s of the interaction portions 62R-2, 62B-2, and 62G-2 in the x direction are sequentially located on the downstream side.

[0056] At the end edge S3 of the substrate 2, the pads 65-1, 65-2, 65-3, and 65-4 of the first ground electrode 61A and the second ground electrode 61B are alternately arranged with the pads 63R, 63B, and 63G of the signal electrode leads 62R-1, 62B-1, and 62G-1.

[0057] In optical modulator 1, downstream terminals 62R-2e, 62B-2e, and 62G-2 of the interaction units 62R-2, 62B-2, and 62G-2 (refer to...) Figure 2 The x-direction positions (coordinates) of the interaction parts 62R-2, 62B-2, and 62G-2 are roughly parallel (roughly aligned in a straight line in the y-direction). The structure that allows for the formation of a structure where "although the x-direction positions (coordinates) of the upstream ends 62R-2s, 62B-2s, and 62G-2s of the interaction parts 62R-2, 62B-2e, and 62G-2e are successively located downstream, the x-direction positions (coordinates) of the downstream ends 62R-2e, 62B-2e, and 62G-2e are roughly parallel" is because the interaction part 62R-2 for red light can be shorter than the interaction part 62B-2 for blue light and the interaction part 62G-2 for green light (LG < LB < LR (refer to...)). Figure 6The x-direction positions (coordinates) of the downstream ends 62R-2e, 62B-2e, and 62G-2e of the interacting parts 62R-2, 62B-2e, and 62G-2e are not limited to being arranged in a roughly straight line in the y-direction. Preferably, the x-direction positions (coordinates) of the downstream ends 62R-2e, 62B-2e, and 62G-2e are within 20% of the length LR of the interacting part 62R-2, more preferably within 15% of the length LR of the interacting part 62R-2, and even more preferably within 10% of the length LR of the interacting part 62R-2.

[0058] The three signal electrode leads 62R-3, 62B-3, and 62G-3 all originate from the downstream ends 62R-2e, 62B-2e, and 62G-2e of the interaction parts 62R-2, 62B-2, and 62G-2 (see reference). Figure 2 ) relative to the direction (x direction) of the extension of the interaction parts 62R-2, 62B-2, and 62G-2, at a specified angle α (refer to Figure 5 The light modulator 1 bends and extends in a manner that does not intersect with each other, crossing the three connecting waveguides 32Rd, 32Bd, and 32Gd when viewed from above, and connects to the pads 64 (64R, 64B, 64G) on the downstream end portion 2B of the signal electrode (i.e., signal electrode 62R) which has the longest interaction portion. The angle α is less than 90°. In the illustrated example, the angle α of the signal electrode leads 62B-3 and 62G-3 is approximately 45°, and the angle α of the signal electrode lead 62R-3 is 90°. The larger the angle α, the shorter the length of the optical modulator 1 (the distance between S1 and S2) can be, so the angle α is preferably 30° or more. The angle α of the multiple signal electrode leads is preferably as follows: one signal electrode lead is 90°, and the other signal electrode leads are less than 90°; or, all signal electrode leads are less than 90°. For example, in the case of three signal electrode leads, the preferred structure is as follows: one signal electrode lead is at 90°, and the remaining two signal electrode leads are less than 90°; or, all three signal electrode leads are less than 90°. When signal electrode lead 62R-3 is bent at 90°, and signal electrode leads 62B-3 and signal electrode leads 62G-3 are bent at angles less than 90°, the length of the optical modulator 1 (the distance between S1 and S2) can be minimized.

[0059] use Figure 5 The enlarged image provides a more detailed explanation.

[0060] In the illustrated example, signal electrode leads 62G-3 and 62B-3 are bent at the same angle α at their downstream ends 62G-2e and 62B-2e, respectively, and have portions 62G-31 and 62B-31 extending parallel to the direction of angle α, and portions 62G-32 and 62B-32 that are further bent and extend toward the end edge S3. On the other hand, signal electrode lead 62R-3 only has a portion that is bent at a predetermined angle and extends toward the end edge S3. The portion 62G-32 of signal electrode lead 62R-3 is parallel to the portion 62G-3 of signal electrode lead 62G-3 and the portion 62B-32 of signal electrode lead 62B-3.

[0061] The reason why the three signal electrode leads 62R-3, 62B-3, and 62G-3 can be configured in this way is that the interaction section 62R-2 for red light only needs to be shorter than the interaction section 62B-2 for blue light and the interaction section 62G-2 for green light (LG < LB < LR (refer to...)). Figure 6 )).

[0062] Furthermore, the photosynthesis section 40 is positioned downstream of the signal electrode (i.e., signal electrode 62G) among the three signal electrodes 62R, 62B, and 62G, which has the shortest interaction section. In other words, the arrangement of the photosynthesis section 40 satisfies the following condition: it is closest to the signal electrode 62G, then close to the signal electrode 62B, and furthest from the signal electrode 62R.

[0063] The bending positions of the three signal electrode leads 62R-3, 62B-3, and 62G-3 (corresponding to the downstream ends 62R-2e, 62B-2e, and 62G-2e of the interaction parts 62R-2, 62B-2, and 62G-2) are approximately parallel in the x-direction (coordinates). Furthermore, the photopolymerization section 40 is positioned downstream of the signal electrode 62G. This structure ensures that the first ground electrode 61A, the second ground electrode 61B, and the signal electrode leads 62R-3, 62B-3, and 62G-3 are positioned so as not to overlap with the photopolymerization section 40 when viewed from above. The reason for this is that by adopting a structure where the first ground electrode, the second ground electrode, and the signal electrode leads are not positioned above the photopolymerization section, changes in the effective refractive index of the lithium niobate forming the photopolymerization section can be prevented, thereby suppressing losses caused by deviations from the design value.

[0064] Not limited to the shape and arrangement of the first ground electrode, the second ground electrode, and the signal electrode lead-out portion shown in this embodiment, by adopting a structure in which the first ground electrode, the second ground electrode, and the signal electrode lead-out portion are not arranged above the photocombining wave portion, it is possible to prevent the effective refractive index of lithium niobate forming the photocombining wave portion from changing, thereby suppressing losses caused by deviations from the design value.

[0065] like Figure 4 As shown in the enlarged view, the preferred arrangement is that the Mach-Zehnder waveguides and signal electrode leads are configured such that, when viewed from above, the signal electrode leads 62R-1, 62B-1, and 62G-1 do not overlap with the optical branches 4a of the Mach-Zehnder waveguides. The reason for this is that by adopting a structure where signal electrode leads through which electrical signals pass are not positioned above the optical branches, changes in the effective refractive index of the lithium niobate forming the optical branches can be prevented, thereby suppressing losses caused by deviations from the design values.

[0066] like Figure 5 As shown in the enlarged view, the preferred arrangement is that the Mach-Zehnder waveguides and signal electrode leads are configured such that, when viewed from above, the signal electrode leads 62R-3, 62B-3, and 62G-3 do not overlap with the optical coupling sections 4b of the Mach-Zehnder waveguides. The reason for this is that by adopting a structure where the signal electrode leads through which electrical signals pass are not positioned above the optical coupling sections, changes in the effective refractive index of the lithium niobate forming the optical coupling sections can be prevented, thereby suppressing losses caused by deviations from the design values.

[0067] The optical modulator of this embodiment is small and can be driven at low voltage. To evaluate miniaturization and low driving voltage, VπL can be used. Vπ is the voltage required for half-wavelength phase modulation (half-wavelength voltage), defined by the difference between the voltage V1 at maximum optical output and the voltage V2 at minimum optical output. Furthermore, L is the length of the portion (interaction section) where the signal electrode overlaps with the optical waveguide (ridge) (interaction length, electrode length). If the interaction length L is long, the half-wavelength voltage Vπ decreases; if the interaction length L is short, the half-wavelength voltage Vπ increases. To reduce the size of the optical modulator, the interaction length L is shortened, and the half-wavelength voltage Vπ increases.

[0068] A smaller VπL indicates a greater ability to achieve the goal of "small size and low drive voltage". Hereinafter, VπL is sometimes referred to as electric field efficiency.

[0069] In this example embodiment, regarding red light with a peak wavelength of 637 nm, green light with a peak wavelength of 520 nm, and blue light with a peak wavelength of 455 nm, the following is used: Figure 6 This example illustrates how the interaction lengths LR, LB, and LG of each visible light beam are adjusted so that Vπ is below 2V. If the voltage is below 2V, CMOS can be used for driving.

[0070] The interaction lengths LR, LB, LG and the half-wavelength voltage Vπ are shown in Table 1. Shortening the interaction lengths LB and LG between green and blue light shortens the length of the optical modulator.

[0071] [Table 1]

[0072] Wavelength [nm] VπL [Vcm] L [cm] Vπ [V] 637 0.95 0.50 1.9 520 0.74 0.41 1.8 455 0.61 0.45 1.4

[0073] exist Figure 6 In the examples shown in Table 1, the preferred structure for combining three visible light beams is as follows: as described later. Figure 8B As shown, a 3-input type and 1-output type (3×1 type) optical combining wave section is used as optical combining wave section 40 to simultaneously combine three visible lights (red light, blue light, and green light) of different wavelengths incident from three connecting waveguides 32Rd, 32Bd, and 32Gd, and output them as a combined wave light to the output waveguide 32e.

[0074] Figure 7 Indicates in Figure 6 The structure shown is a modified example in which the positions of the Mach-Zehnder waveguide 32B for blue light and the Mach-Zehnder waveguide 32G for green light are changed.

[0075] This variation refers to an example where the interaction lengths LR, LB, and LG of each visible light ray are adjusted in such a way that Vπ is below 2V.

[0076] The interaction lengths LR, LB, LG and the half-wavelength voltage Vπ are shown in Table 2. Similarly, shortening the interaction lengths LB and LG between green and blue light shortens the length of the optical modulator.

[0077] [Table 2]

[0078] Wavelength [nm] VπL [Vcm] L [cm] Vπ [V] 637 0.95 0.50 1.9 520 0.74 0.45 1.6 455 0.61 0.41 1.5

[0079] exist Figure 7 In the examples shown in Table 2, the preferred structure for combining the three visible light beams is as follows: as described later. Figure 8C As shown, two optical wave combiners 40-1 and 40-2 (2×1 type) with 2 inputs and 1 output are used as the optical wave combiner 40. First, the optical wave combiner 40-1 combines two visible lights (red light and green light) with different wavelengths that are incident from the two connecting waveguides 32Rd and 32Gd. Then, the optical wave combiner 40-2 combines the combined light with visible light (blue light) that is incident from the connecting waveguide 32Bd and outputs it as a combined light to the output waveguide 32e.

[0080] (High-speed modulation)

[0081] 4K resolution is 3840×2160, requiring high-speed drive (high-speed modulation) of 1GHz or higher. The modulation performed by the optical modulator in this embodiment is voltage-controlled, enabling high-speed modulation compared to current-controlled modulation by a laser source. Furthermore, since the optical waveguide layer is composed of a lithium niobate film, high-speed drive (high-speed modulation) of 1GHz or higher is possible. The optical modulator in this embodiment is designed with a bandwidth of 10GHz.

[0082] (Substrate 2)

[0083] Regarding substrate 2, there are no particular limitations as long as its refractive index is lower than that of the lithium niobate film forming the optical waveguide layer 3. Examples include sapphire substrates, Si substrates, and thermally oxidized silicon substrates. Preferably, the lithium niobate film can be formed as an epitaxial film on substrate 2.

[0084] Since the optical waveguide layer is composed of a lithium niobate (LiNbO3) film, there are no particular limitations on the substrate 2 as long as its refractive index is lower than that of the lithium niobate film. However, as a substrate capable of forming a single-crystal lithium niobate film as an epitaxial film, a sapphire single-crystal substrate or a single-crystal silicon substrate is preferred. There are no particular limitations on the crystal orientation of the single-crystal substrate. For example, a c-axis oriented lithium niobate film has a 3-fold symmetry, so it is preferable that the single-crystal substrate also has the same symmetry. In the case of a sapphire single-crystal substrate, a substrate with the c-plane is preferred, and in the case of a single-crystal silicon substrate, a substrate with the (111)-plane is preferred.

[0085] (Optical waveguide layer 3)

[0086] The optical waveguide layer 3 is composed of a lithium niobate film. The lithium niobate forming the lithium niobate film can contain elements other than lithium (Li), niobium (Nb), and oxygen (O).

[0087] Lithium niobate can be, for example, a compound represented by the following formula (I).

[0088] Li x NbA y O z (I)

[0089] (In formula (I), A represents elements other than Li, Nb, and O. x represents numbers greater than 0.5 and less than 1.2. y represents numbers greater than 0 and less than 0.5. z represents numbers greater than 1.5 and less than 4.0.)

[0090] In formula (I), A can be any element other than Li, Nb, and O. Examples include K, Na, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Cr, Mo, W, Fe, Co, Ni, Zn, Sc, and Ce. A can be selected from only one of these elements or from two or more.

[0091] In formula (I), x is a number greater than or equal to 0.5 and less than 1.2, preferably a number greater than or equal to 0.9 and less than 1.05. y is a number greater than or equal to 0 and less than 0.5. z is a number greater than or equal to 1.5 and less than 4.0, preferably a number greater than or equal to 2.5 and less than 3.5.

[0092] The lithium niobate film forming the optical waveguide layer 3 is preferably an epitaxial film.

[0093] Lithium niobate films, for example, are lithium niobate films with a c-axis orientation. Lithium niobate films are, for example, epitaxial films grown epitaxially on substrate 2. Epitaxial films are single-crystal films whose crystal orientation is uniformly determined by the substrate. Epitaxial films have a single crystal orientation in the z-direction and xy-plane directions, with the crystals aligned in the x-axis, y-axis, and z-axis directions. Whether a film formed on substrate 2 is an epitaxial film can be confirmed, for example, by confirming the peak intensity and poles at the orientation position in 2θ-θ x-ray diffraction.

[0094] The optical waveguide layer 3 has a plurality of flat portions 31 and ridges 32 arranged between adjacent flat portions 31, having a shape that rises in a strip from the flat portions 31. In the optical modulator 1 of this embodiment, the input waveguide 32a, the optical branch portion 4a, the first ridge waveguide 32c branching from the input waveguide 32a, the second ridge waveguide 32b, the optical coupling portion 4b that couples them, and the output waveguide 32d, described later, are collectively referred to as a ridge 32.

[0095] The number of ridges 32, n, is an integer greater than or equal to 2. Figures 1-5 In the image, three examples (n=3) are represented. Visible light of different wavelengths is incident on three ridges: 32R, 32G, and 32B.

[0096] In this embodiment, for example, red light with a peak wavelength of 610 nm or more and 750 nm or less is incident on ridge 32R. Green light with a peak wavelength of 500 nm or more and 560 nm or less is incident on ridge 32G. Blue light with a peak wavelength of 435 nm or more and 480 nm or less is incident on ridge 32B. Since the three ridges 32R, 32G, and 32B of the light modulator 1 in this embodiment are respectively irradiated with red light, green light, and blue light, it can be preferably used, for example, in XR glasses capable of displaying full-color images.

[0097] The three ridges 32R, 32G, and 32B each have an input waveguide 32a, an optical branch section 4a, a first ridge waveguide 32c, a second ridge waveguide 32b, an optical coupling section 4b, and an output waveguide 32d.

[0098] In the three ridges 32R, 32G, and 32B of the optical waveguide layer 3, the input waveguide 32a has a generally rectangular cross-section and is incident with visible light generated by a light source such as a laser element. The input waveguide 32a branches at the optical branching section 4a into a first ridge waveguide 32c and a second ridge waveguide 32b. The first ridge waveguide 32c and the second ridge waveguide 32b may also have a trapezoidal cross-section. In this embodiment, the first ridge waveguide 32c and the second ridge waveguide 32b have the same cross-sectional shape. The first ridge waveguide 32c and the second ridge waveguide 32b are coupled through the optical coupling section 4b to form the output waveguide 32d. The output waveguide 32d has a generally rectangular cross-section and emits the visible light signal generated in the optical coupling section 4b.

[0099] The cross-sectional shape of the input waveguide 32a and the output waveguide 32d is not limited to a rectangle; for example, it can be a trapezoid or a semicircle.

[0100] In addition, the cross-sectional shape of the first ridge waveguide 32c and the second ridge waveguide 32b is not limited to a trapezoid; for example, it can be a rectangle or a semicircle.

[0101] In addition, the cross-sectional shapes of the input waveguide 32a, the output waveguide 32d, the first ridge waveguide 32c, and the second ridge waveguide 32b can be symmetrical or asymmetrical.

[0102] When the optical modulator of this embodiment is used in a glasses-type image display device, the thickness (T) of the flat portion 31 of the optical waveguide layer 3 is... slab The preferred thickness is 0.1–0.3 μm. Furthermore, the thickness (T) of the ridge 32 of the optical waveguide layer 3 is... R The preferred size is 0.5–1.0 μm.

[0103] This is because: if the thickness of ridge 32 (T) R If the thickness of the ridge is small, light will not propagate; if the thickness of the ridge is small (T), light will not propagate. R If the light intensity is high, then the propagated light becomes multimode.

[0104] When the light modulator of this embodiment is used in an eyeglass-type image display device, the center-to-center distance (S) between the ridges 32 is preferably 2 μm to 12 μm.

[0105] This is because reducing S can shorten the distance between the signal electrode and the ground electrode, thereby improving the efficiency of the electric field imparted to the ridge 32.

[0106] exist Figure 3 The ridges 32b and 32c shown can be designed as trapezoidal shapes that are symmetrical about the center line.

[0107] When the light modulator of this embodiment is used in an eyeglass-type image display device, in this shape, the tilt angle (α) of the ridges 32b and 32c is preferably 60 to 90 degrees. This is because when the tilt angle becomes smaller, the propagating light becomes multimode.

[0108] Additionally, the width (W) of the upper surface of ridges 32b and 32c R The preferred size is 0.3–1.2 μm.

[0109] This is because: if the waveguide width is small, light does not propagate; if the waveguide width is large, the propagating light becomes multimode.

[0110] The optical combining section 40 can use an optical combining section with a known structure. For example, an MMI (Multi-Mode Interferometer) type combiner, a Y-type combiner, a directional coupler, etc., can be used.

[0111] (Protective layer 51)

[0112] like Figure 3 As shown, a protective layer 51 is disposed between the planar portion 31 of the optical waveguide layer 3 and the buffer layer 52. The protective layer 51 is made of a dielectric material with a refractive index lower than that of the optical waveguide layer 3. Materials for the protective layer 51 can include, for example, silicon oxide (SiO2), aluminum oxide (Al2O3), lanthanum oxide (La2O3), or composites of these oxides. Examples of composites of these oxides include LaAlSiInO. Among these materials, silicon oxide (SiO2) is preferred as the material for the protective layer 51.

[0113] (Buffer layer 52)

[0114] A buffer layer 52 is formed on the optical waveguide layer 3 and the protective layer 51 to prevent visible light propagating in the optical waveguide layer 3 from being absorbed by the electrode layer.

[0115] The buffer layer 52 is made of a dielectric material with a refractive index lower than that of the optical waveguide layer 3.

[0116] The dielectric constant of the dielectric material constituting the buffer layer 52 is preferably 7 or higher. This is because it can reduce the electric field efficiency VπL.

[0117] Examples of materials for the buffer layer 52 include aluminum oxide (Al2O3, dielectric constant 7) and LaAlSiInO (dielectric constant 11).

[0118] The material of the buffer layer 52 can be the same as that of the protective layer 51, or it can be a different material from that of the protective layer 51.

[0119] The thickness of buffer layer 52 (T) bufferThe preferred size is 0.4 μm or larger and 1 μm or smaller. This is because it can reduce the electric field efficiency VπL.

[0120] (Electrode layer)

[0121] As an electrode layer, it includes: a signal electrode 62 formed on the buffer layer 52; and a first ground electrode 61A and a second ground electrode 61B disposed on both sides of the signal electrode 62.

[0122] The optical modulator of this embodiment is a so-called single-drive type optical modulator with one signal electrode. The so-called dual-drive type optical modulator with two signal electrodes has a complex electrode structure, requiring the application of the signal while simultaneously controlling the phase of the inverted electrical signal on both electrodes, thus resulting in a complex circuit structure for the drive system. Since the optical modulator of this embodiment is a single-drive type, it does not have this problem.

[0123] When the light modulator of this embodiment is used in an eyeglass-type image display device, the width (We) of the signal electrode 62 is preferably 1.0 to 4.0 μm.

[0124] This is because it can reduce the electric field efficiency VπL.

[0125] When the light modulator of this embodiment is used in an eyeglass-type image display device, the width of the first ground electrode 61A and the second ground electrode 61B is preferably 50 μm to 1000 μm.

[0126] This is because when the grounding electrode is thin, the voltage will not become 0V, and the electric field efficiency VπL increases.

[0127] When the light modulator of this embodiment is used in an eyeglass-type image display device, the thickness (Te) of the electrode layer is preferably 0.1 to 5 μm.

[0128] This is because, at high modulation frequencies, the electrode with the larger cross-sectional area can propagate microwaves more efficiently.

[0129] When the light modulator of this embodiment is used in an eyeglass-type image display device, the distance (G) between the signal electrode 62 and the ground electrode 61 is preferably 1 μm to 12 μm.

[0130] This is because it can reduce the electric field efficiency VπL.

[0131] (The way multiple visible light beams combine)

[0132] Figures 8A-8C This is a diagram used to illustrate how multiple visible light beams combine.

[0133] Figure 8B and Figure 8CThe image shown is enlarged. Figure 8A A planar schematic diagram of the vicinity of the optically synthesized wave section 40, indicated by arrow B.

[0134] exist Figure 8B In the illustrated configuration, a 3-input, 1-output (3×1 type) optical combiner is used as the optical combiner 40. It simultaneously combines three visible lights (red, blue, and green) of different wavelengths incident from three connecting waveguides 32Rd, 32Bd, and 32Gd, and outputs a single combined beam to the output waveguide 32e. Similarly, when there are multiple (n) visible lights other than three, an n-input, 1-output (n×1 type) optical combiner can be used to simultaneously combine n visible lights into a single combined beam.

[0135] Figure 8C The illustrated method uses two 2-input, 1-output (2×1 type) photocombining units 40-1 and 40-2 as photocombining unit 40. This type of photocombining unit is referred to as a two-stage photocombining unit. Correspondingly, Figure 8B The type of photosynthetic waveguide shown is called a first-order structure photosynthetic waveguide.

[0136] First, two visible lights (red and blue) of different wavelengths incident from the two connecting waveguides 32Rd and 32Bd are combined in optical combining section 40-1. Then, this combined light is combined with visible light (green) incident from the connecting waveguide 32Gd in optical combining section 40-2 and emitted as a single combined light to the output waveguide 32e. Figure 8C In the example shown, red and blue light are combined first, and then green light is combined. However, the combination of visible light that is combined first and visible light that is combined later is not limited to this example.

[0137] (High-order mold removal section)

[0138] The optical modulator of this embodiment may also have a high-order mode removal section configured to remove high-order modes on the waveguides upstream of each of the multiple Mach-Zehnder waveguides before the branches of the first and second ridge waveguides.

[0139] Figure 9 This is a magnified planar schematic diagram of the vicinity of the higher-order mode removal section of the optical modulator 1. The parts enclosed by the dashed box are the higher-order mode removal sections 32Ra1, 32Ba1, and 32Ga1.

[0140] The higher-order mode removal section is a part constructed in such a way that the fundamental mode (0th order mode (single mode)) and higher-order modes (1st order mode, 2nd order mode, ... (multi-mode)) of each visible light are passed with low loss and the higher-order modes are passed with high loss.

[0141] As a structure for higher-order mold removal, such as Figure 9 As shown, a curved waveguide can be illustrated. Other examples of higher-order mode removal structures include structures that remove higher-order modes by setting the linewidth of the optical waveguide to a predetermined width.

[0142] Regarding adoption Figure 9 The curved waveguide shown is a structure for removing higher-order modes. Below is a specific dimensional example of removing higher-order modes to become a single mode.

[0143] Simulations confirmed that when using red light with a peak wavelength of 637 nm, green light with a peak wavelength of 520 nm, and blue light with a peak wavelength of 455 nm, with the width of the optical waveguide set to the dimensions shown in Table 3, and the radius of curvature of the curved waveguide set to 200 μm, higher-order modes are removed and become single-mode.

[0144] [Table 3]

[0145] Wavelength [nm] Waveguide width [μm] 637 0.4 520 0.5 455 0.6

[0146] [Manufacturing Method]

[0147] Figure 1 The optical modulator 1 of this embodiment shown can be manufactured, for example, by the method described below. First, an optical waveguide layer 3 composed of a lithium niobate film is formed on a substrate 2.

[0148] As a method for forming a lithium niobate film on substrate 2, thin film formation methods such as sputtering, CVD, and sol-gel methods can be used.

[0149] When using a sapphire single crystal substrate as substrate 2, lithium niobate film can be directly epitaxially grown on the sapphire single crystal substrate.

[0150] When using a monocrystalline silicon substrate as substrate 2, a lithium niobate film can be formed by epitaxial growth through a cladding layer. As the cladding layer, a cladding layer with a lower refractive index than the lithium niobate film and suitable for epitaxial growth is used. Specifically, a cladding layer composed of Y₂O₃ can be used, for example. By epitaxially growing a lithium niobate film on a monocrystalline silicon substrate through a cladding layer composed of Y₂O₃, a high-quality lithium niobate film can be formed.

[0151] Next, the lithium niobate film thus obtained is formed into the desired pattern shape using known methods such as photolithography. This results in an optical waveguide layer 3 having multiple flat portions 31 and n ridges 32 disposed between adjacent flat portions 31.

[0152] Next, a protective layer 51 is formed on the flat portion 31 of the optical waveguide layer 3 using a thin film formation method such as sputtering, CVD, or sol-gel.

[0153] Next, a buffer layer 52 is formed over the protective layer 51 and over the ridge 32 of the optical waveguide layer 3. Known methods can be used to form the buffer layer 52. Specifically, thin film formation methods such as sputtering, CVD, and sol-gel methods can be used to form the buffer layer 52.

[0154] Next, an electrode layer is formed on the buffer layer 52, for example, using the method shown below.

[0155] First, a metal thin film is formed on the buffer layer 52 using a thin film formation method such as vapor deposition, sputtering, CVD, or sol-gel method. Next, the metal thin film is formed into a desired pattern shape using a known method such as photolithography. This forms an electrode layer having a plurality of first ground electrodes 61A and second ground electrodes 61B arranged in a strip shape in the top view, and a plurality of signal electrodes 62 arranged in a strip shape in the top view.

[0156] Electrode layers can be formed using methods such as vapor deposition or sputtering to form thin metal films through a mask of the desired shape.

[0157] Through the above procedures, the optical modulator 1 of this embodiment is obtained.

[0158] [Light Source Module]

[0159] Figure 10 A plan view illustrating a light source module according to one embodiment of the present invention.

[0160] The light source module has an optical modulator as described above and multiple light sources that emit visible light that is incident on multiple input waveguides of the optical modulator.

[0161] Figure 10 The light source module 100 shown has three light sources 7R, 7G, and 7B as light sources 7. Each light source 7R, 7G, and 7B emits visible light that is incident on the input waveguide 32a of the Mach-Zehnder waveguide 32 (32R, 32G, 32B) in the optical waveguide layer 3 of the optical modulator 1. For example, light source 7R can emit red light, light source 7G can emit green light, and light source 7B can emit blue light.

[0162] As light sources, the 7R, 7G, and 7B can use laser elements such as laser diodes (LDs) and can use various commercially available laser elements.

[0163] Figure 11 It is cut by XZ plane Figure 10 A cross-sectional schematic diagram of a portion of the light source module 100 shown. Only a portion near the joint is depicted.

[0164] The light source 7 is disposed on the upper surface of the light source base 20. The light source base 20 can be a light source base shared by all light sources, or it can be a light source base that is independently disposed for each light source.

[0165] The light source base 20 is made of, for example, aluminum nitride (AlN), aluminum oxide (Al2O3), silicon (Si), etc.

[0166] The light source base 20 and the optical waveguide substrate 2 on which the optical waveguide layer is formed can be configured to be directly bonded via the metal layer 70. According to this structure, spatial coupling or fiber coupling is not required, and miniaturization can be further achieved.

[0167] By configuring the structure in which the bonding surface 20A of the light source base 20 and the bonding surface 2A of the optical waveguide substrate 2 are bonded via the metal layer 70, the relative position of the light source base 20 and the optical waveguide substrate 2 can be adjusted during manufacturing, and the optical axis position of the laser can be aligned (active alignment) in such a way that the optical axis of each light source 7 is aligned with the axis of the input waveguide.

[0168] Metal layer 70 can be composed of multiple metal layers.

[0169] When the light source module of this embodiment is used in XR glasses, considering the light intensity required by XR glasses, the gap (spacing) S between the bonding surface 20A of the light source base 20 and the bonding surface 2A of the substrate 2 for the optical waveguide is preferably greater than 0 μm and less than 5 μm.

[0170] (Driver Method)

[0171] An optical modulator can modulate input light into output light using a high-frequency modulation voltage and a DC bias voltage. The operating point Vd of the optical modulator is adjusted by controlling the DC bias voltage Vdc. The operating point Vd is the voltage that forms the center of the modulation voltage amplitude Vpp. The half-wavelength voltage of the high-frequency modulation voltage is set as Vπ(RF).

[0172] [Optical engine and XR glasses]

[0173] Figure 12 This is a conceptual diagram illustrating an example of the XR glasses of the present invention. Figure 13 It means in Figure 12 The diagram shows a concept of XR glasses in which an image is projected directly onto the retina using a laser emitted from a light source module.

[0174] The XR glasses (glasses) 1000 in this embodiment are glasses-type terminals. XR is a general term for Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality.Figure 13 The symbol L shown represents the image display light.

[0175] Figure 12 The XR glasses 1000 shown in this embodiment are in the form of the light source module 100 of the above embodiment mounted on the optical engine 5001 provided on the frame 1010.

[0176] like Figure 12 As shown, the optical engine 5001 includes a light source module 100, an optical scanning mirror 3001, an optical system 2001 combining the light source module 100 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.

[0177] As the optical scanning mirror 3001, a MEMS mirror can be used, for example. In order to project a 2D image, as the optical scanning mirror 3001, a biaxial MEMS mirror that vibrates in a manner that changes the angle in the horizontal direction (X direction) and the vertical direction (Y direction) to reflect the laser is preferably used.

[0178] The optical system 2001 performs optical processing on the laser emitted from the light source module 100. As the optical system 2001, for example, an optical system equipped with a collimating lens 2001a, a slit 2001b, and an ND filter 2001c can be used. Figure 12 The optical system 2001 shown is one example, but other structures are also possible.

[0179] exist Figure 12 In the XR glasses 1000 of this embodiment shown, as Figure 13 As shown, the laser R irradiated by the light source module 100 mounted on the frame 1010 is reflected by the light scanning mirror 3001, and then reflected by the lens 4001 of the XR glasses 1000. It enters the human eyeball E as the image display light L, and can directly project an image (picture) onto the retina M.

[0180] The XR glasses 1000 of this embodiment are equipped with the light source module 100 of this embodiment, so the electric field efficiency can be reduced.

[0181] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the structures and combinations thereof in each embodiment are merely examples, and structural additions, omissions, substitutions and other changes can be made without departing from the spirit of the present invention.

[0182] [Explanation of reference numerals in the attached figures] 1. Optical modulator; 2 substrate; 3. Optical waveguide layer; 32. Ridge; 32b Second ridge waveguide; 32c First ridge waveguide; 40. Photosynthetic wavelet; 52. Buffer layer; 61A First grounding electrode; 61B Second grounding electrode; 62R, 62B, 62G signal electrodes; 100 Light Source Modules.

Claims

1. An optical modulator, wherein, have: substrate; An optical waveguide layer made of lithium niobate is formed on the substrate, and multiple Mach-Zehnder waveguides are arranged in parallel, wherein the Mach-Zehnder waveguides include a first ridge waveguide and a second ridge waveguide for transmitting visible light. A buffer layer formed on the optical waveguide layer; Multiple signal electrodes are formed on the buffer layer and have interaction sections arranged along the multiple Mach-Zehnder waveguides respectively; as well as A plurality of first ground electrodes and a plurality of second ground electrodes are disposed separately from the signal electrodes on both sides of the plurality of signal electrodes. The signal electrode is positioned above the first ridge waveguide. The second ground electrode is positioned above the second ridge waveguide. The optical modulator also features: A signal electrode lead-out portion connects the signal electrode to a pad disposed on the end edge of the substrate; The optically synthesized wave section is disposed on the downstream side of the plurality of Mach-Zehnder waveguides and combines multiple visible light waves that have passed through the plurality of Mach-Zehnder waveguides. Multiple connecting waveguides connect the downstream sides of the multiple Mach-Zehnder waveguides to the optically synthesized wave section; and An output waveguide connected to the optically synthesized wave section, The first grounding electrode, the second grounding electrode, and the signal electrode lead-out portion are positioned so as not to overlap with the photosynthetic wave portion when viewed from above.

2. The optical modulator as claimed in claim 1, wherein, The Mach-Zehnder waveguides are three or more. The plurality of signal electrodes comprises three or more, and each electrode has three or more interacting parts arranged parallel to each other in a top view, starting from the shorter side. The photosynthesis wave section is positioned downstream of the signal electrode among the plurality of signal electrodes, which has the shortest interaction section. The plurality of signal electrode leads are three or more. Two or more of the signal electrode leads extend from the downstream end of the interaction section in a direction that does not intersect each other at a direction less than 90° relative to the direction of extension of the interaction section, cross the plurality of connecting waveguides when viewed from above, and are connected to a pad disposed on the downstream end edge of the signal electrode of the interaction section having the longest length.

3. The optical modulator as described in claim 1, wherein, Each of the plurality of Mach-Zehnder waveguides has a higher-order mode removal section configured to remove higher-order modes on the waveguide upstream of each of the first and second ridge waveguides.

4. The optical modulator as claimed in claim 1, wherein, The width of the signal electrode is greater than 1 μm and less than 4 μm.

5. The optical modulator as claimed in claim 1, wherein, The distance between the signal electrode and the first ground electrode, and the distance between the signal electrode and the second ground electrode, are greater than 1 μm and less than 12 μm.

6. A light source module, wherein, have: The optical modulator according to any one of claims 1 to 5; and Multiple light sources are connected to the multiple Mach-Zehnder waveguides, and the emitted light is visible light that is incident on the multiple input waveguides respectively.

7. The light source module as described in claim 6, wherein, The plurality of light sources are each disposed on the upper surface of a separate light source base. The light source base is bonded to the substrate via a metal layer. The distance between the mating surface of the light source base and the mating surface of the substrate is less than 5 μm.

8. An optical engine, wherein, have: The light source module as described in claim 7; and A light scanning mirror reflects light emitted from the light source module at varying angles to display images.

9. An XR pair of glasses, wherein, It is equipped with the optical engine as described in claim 8.

10. A method for manufacturing a light source module, wherein, This method is a method for manufacturing the light source module as described in claim 7. The method includes the following steps: while monitoring the light output, the relative position of the light source base and the substrate is adjusted by active alignment, and the light source base and the substrate are bonded together through a metal layer.

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