Optical element and laser module

Abstract

To provide an optical element capable of converting the polarization mode of visible light and a laser module.SOLUTION: A core layer of the optical element includes a conversion unit 42 for converting the polarization mode of visible light between a TM0 mode and a TE1 mode. The conversion unit 42 comprises an upper tapered part 46 and a lower tapered part 47 which are stacked in the direction of an axis Z. In a conversion region 42d, the width of the upper tapered part 46 continuously increases from width W0 to width Wt from a connecting end 42a toward an intermediate position 42c, and the width of the lower tapered part 47 continuously increases from width W0 to width Ws from the connecting end 42a toward the intermediate position 42c. In a conversion region 42e, the width of the upper tapered part 46 continuously increases from width Wt to width W1 from the intermediate position 42c toward the connecting end 42b, and the width of the lower tapered part 47 continuously decreases from width Ws toward width W1 from the intermediate position 42c to the connecting end 42b.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to an optical device and a laser module. [Background technology]

[0002] The polarization modes of light propagating through an optical waveguide include a TE (Transverse Electric) mode, which is a polarization mode having a main electric field horizontal to the substrate, and a TM (Transverse Magnetic) mode, which is a polarization mode having a main electric field vertical to the substrate. Optical waveguide elements that convert these polarization modes are known. For example, Patent Document 1 describes an optical waveguide element that has a tapered shape whose width increases continuously from the input end to the output end, and includes a core with a V-shaped cross-sectional groove formed on the upper surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-34349 A Summary of the Invention [Problem to be solved by the invention]

[0004] The optical waveguide element described in Patent Document 1 converts light in TM0 mode having a wavelength of 1550 nm into light in TE1 mode, but does not take visible light into consideration.

[0005] The present disclosure describes optical elements and laser modules capable of converting the polarization mode of visible light. [Means for solving the problem]

[0006] An optical element according to one aspect of the present disclosure includes a substrate having a main surface, and a core layer provided on the main surface and made of a material having an electro-optic effect. The core layer includes a mode converter extending in a first direction along the main surface and converting a polarization mode of visible light between TM0 mode and TE0 mode. The mode converter includes an input section located at one end of the mode converter in the first direction and receiving visible light of a first polarization mode which is one of the TM0 mode and the TE0 mode, an output section located at the other end of the mode converter in the first direction and outputting visible light of a second polarization mode which is the other of the TM0 mode and the TE0 mode, a first conversion section provided between the input section and the output section and converting the polarization mode of the visible light between the TM0 mode and the TE1 mode, and a second conversion section provided between the input section and the output section and converting the polarization mode of the visible light between the TE0 mode and the TE1 mode. The first conversion section includes a first end and a second end, which are both ends in a first direction, and an upper tapered section and a lower tapered section stacked in a second direction intersecting with the main surface. In a first region from the first end of the first conversion section to a middle position between the first end and the second end, the length of the upper tapered section in a third direction intersecting with the first and second directions increases continuously from the first length to a second length longer than the first length from the first end toward the middle position, and the length of the lower tapered section in the third direction increases continuously from the first length to a third length longer than the second length from the first end toward the middle position. In a second region from the middle position to the second end of the first conversion section, the length of the upper tapered section in the third direction increases continuously from the second length to a fourth length longer than the second length and shorter than the third length from the middle position toward the second end, and the length of the lower tapered section in the third direction decreases continuously from the third length to the fourth length from the middle position toward the second end.

[0007] In this optical element, the first conversion section converts the polarization mode of visible light between the TM0 mode and the TE1 mode. In the first conversion section, the upper tapered section and the lower tapered section are stacked in the second direction, and the first conversion section has asymmetry in the second direction. In the first conversion section, the effective refractive index of the TM0 mode and the effective refractive index of the TE1 mode approach each other as the distance from the first end increases, so that conversion between the TM0 mode and the TE1 mode is induced. For example, when visible light in the TM0 mode is incident on the first end of the first conversion section, the polarization mode of the visible light is converted from the TM0 mode to the TE1 mode in the first conversion section, and then converted from the TE1 mode to the TE0 mode in the second conversion section. Similarly, when visible light in the TE0 mode is incident on the second conversion section, the polarization mode of the visible light is converted from the TE0 mode to the TE1 mode in the second conversion section, and then converted from the TE1 mode to the TM0 mode in the first conversion section. As described above, it is possible to convert the polarization mode of visible light between the TM0 mode and the TE0 mode.

[0008] The first polarization mode may be a TM0 mode, and the second polarization mode may be a TE0 mode. The first end may be connected to the input portion. The second conversion portion may be provided between the first conversion portion and the output portion. In this case, visible light input in the TM0 mode can be output in the TE0 mode.

[0009] The first polarization mode may be a TE0 mode, and the second polarization mode may be a TM0 mode. The first end may be connected to the output section. The second conversion section may be provided between the input section and the first conversion section. In this case, visible light incident in the TE0 mode can be output in the TM0 mode.

[0010] The length of the first conversion section in the first direction may be 360 ​​μm or more and 1010 μm or less. The second length may be 0.5 μm or more and 1.0 μm or less. The third length may be 1.0 μm or more and 5.0 μm or less. In this case, the loss of light intensity in the conversion between the TM0 mode and the TE1 mode can be reduced. Therefore, the conversion efficiency between the TM0 mode and the TE1 mode can be improved.

[0011] The second conversion section may include a first asymmetric section having an asymmetric shape in the third direction, the length of which in the third direction increases continuously from the fifth length to a sixth length longer than the fifth length as it moves away from the first conversion section, a second asymmetric section having an asymmetric shape in the third direction, the length of which in the third direction decreases continuously from the sixth length to a seventh length shorter than the sixth length as it moves away from the first conversion section, and a connection section provided between the first asymmetric section and the second asymmetric section, the length of which in the third direction is the sixth length over the entire length in the first direction. In this case, the second conversion section has asymmetry in the third direction. For example, when visible light in the TE1 mode is incident on the second conversion section, two components of the TE1 mode that are in opposite phase to each other propagate with different effective optical path lengths, and therefore different phase changes occur in the two components. By setting the length in the first direction of the first asymmetric section, the length in the first direction of the second asymmetric section, the length in the first direction of the connection section, the fifth length, the sixth length, and the seventh length so that a phase matching condition in which the two components are in phase is satisfied, visible light in TE0 mode is output from the second conversion section. Similarly, when visible light in TE0 mode is incident on the second conversion section, visible light in TE1 mode is output from the second conversion section. As described above, it is possible to convert the polarization mode of visible light between TE0 mode and TE1 mode.

[0012] The length of the second conversion section in the first direction may be 40 μm or more and 100 μm or less. The length of the second conversion section in the third direction may be 0.4 μm or more and 1.2 μm or less. In this case, the loss of light intensity in the conversion between the TE0 mode and the TE1 mode can be reduced. Therefore, the conversion efficiency between the TE0 mode and the TE1 mode can be improved.

[0013] The mode converter may further include a connecting portion that connects the first conversion portion and the second conversion portion. The length of the connecting portion in the third direction may be constant over the entire length of the connecting portion in the first direction. In a configuration in which the first conversion portion and the second conversion portion are connected by extending the upper tapered portion of the first conversion portion, if the length of the upper tapered portion in the third direction is too wide, unnecessary higher-order modes are generated in visible light, and the conversion efficiency decreases. Therefore, in this configuration, restrictions are imposed on the design of the optical element, such as reducing the distance between the first conversion portion and the second conversion portion. On the other hand, in a configuration in which the first conversion portion and the second conversion portion are connected by a connecting portion having a constant length in the third direction, the distance between the first conversion portion and the second conversion portion can be adjusted to a desired length by setting the length of the connecting portion in the third direction to a length at which unnecessary higher-order modes are not generated. Therefore, the degree of freedom in designing the optical element can be improved.

[0014] The core layer may further include a first mode converter that is a mode converter that converts the polarization mode of the red light from the first polarization mode to the second polarization mode, a second mode converter that is a mode converter that converts the polarization mode of the green light from the first polarization mode to the second polarization mode, a third mode converter that is a mode converter that converts the polarization mode of the blue light from the first polarization mode to the second polarization mode, and a multiplexer that multiplexes the red light, the green light, and the blue light and outputs a laser beam. In this case, the polarization modes of the red light, the green light, and the blue light are converted from the first polarization mode to the second polarization mode. By using a polarization mode with high multiplexing efficiency in the multiplexer as the second polarization mode, out of the TM0 mode and the TE0 mode, it is possible to improve the multiplexing efficiency.

[0015] The core layer may further include a first modulator for modulating the light intensity of the red light, a second modulator for modulating the light intensity of the green light, and a third modulator for modulating the light intensity of the blue light. In order to output full-color laser light by combining the red light, the green light, and the blue light, it is necessary to adjust the light intensity of each color of light according to the color to be output. According to the above configuration, the light intensity of the red light, the green light, and the blue light are modulated, so that it is possible to output full-color laser light.

[0016] A laser module according to another aspect of the present disclosure includes the optical element, a first light source that emits red light in a first polarization mode, a second light source that emits green light in the first polarization mode, and a third light source that emits blue light in the first polarization mode. Since the laser module includes the optical element, it is possible to convert the polarization mode of visible light. Effect of the Invention

[0017] According to each aspect and embodiment of the present disclosure, the polarization mode of visible light can be converted. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing the appearance of a near-eye wearable device to which a laser module according to an embodiment is applied. [Diagram 2] FIG. 2 is a schematic diagram of the retinal projection device shown in FIG. [Diagram 3] FIG. 3 is a plan view of the laser module shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is an enlarged view of a portion of the mode converter shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is an enlarged view of a portion of the mode converter shown in FIG. [Figure 8]FIG. 8 is an enlarged view of the modulator shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a plan view of a laser module including an optical element according to another embodiment. [Figure 11] FIG. 11 is a plan view of a laser module including an optical element according to yet another embodiment. [Figure 12] FIG. 12 is a plan view of a laser module including an optical element according to yet another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same symbols, and duplicated descriptions are omitted. An XYZ coordinate system may be shown in each drawing. The Y-axis direction (third direction) is a direction that intersects (e.g., perpendicular to) the X-axis direction (first direction) and the Z-axis direction (second direction). The Z-axis direction is a direction that intersects (e.g., perpendicular to) the X-axis direction and the Y-axis direction. In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values ​​written before and after "~" as the minimum and maximum values, respectively. Individually described upper and lower limit values ​​can be arbitrarily combined.

[0020] An application example of a laser module according to an embodiment will be described with reference to FIG. 1. FIG. 1 is a perspective view showing the appearance of a near-eye wearable device to which a laser module according to an embodiment is applied. The near-eye wearable device 1 shown in FIG. 1 is a device that projects an image onto the retina of a user wearing the near-eye wearable device 1. The near-eye wearable device 1 is, for example, a head-mounted device, and may take the form of glasses, goggles, hats, helmets, and the like. Examples of the near-eye wearable device 1 include smart glasses such as AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses. The near-eye wearable device 1 includes a frame 2, a lens 3, and a retinal projection device 10.

[0021] The frame 2 includes a pair of rims 2a, a bridge 2b, and a pair of temples 2c. The rims 2a are portions that hold the lenses 3. The bridge 2b is a portion that connects the pair of rims 2a. The temples 2c are portions that extend from the rims 2a and are hung on the ears of a user. The frame 2 may be a rimless frame. The lenses 3 have an inner surface 3a (see FIG. 2) that faces the eyeball of a user wearing the near eyewear wearable device 1.

[0022] The retinal projection device 10 is a device that directly projects (draws) an image onto the retina of a user wearing the near-eye wearable device 1. The retinal projection device 10 is mounted on the near-eye wearable device 1. In this embodiment, the near-eye wearable device 1 includes two retinal projection devices 10 in order to project images onto both the left and right retinas, but may include only one of the retinal projection devices 10.

[0023] Next, the retinal projection device 10 will be described in detail with reference to Fig. 2. Fig. 2 is a schematic diagram of the retinal projection device shown in Fig. 1. As shown in Fig. 2, the retinal projection device 10 includes an optical engine 11 and a reflector 12.

[0024] The optical engine 11 is a device that generates laser light Ls having a color and light intensity corresponding to the pixels of an image to be projected onto the retina, and emits the laser light Ls to the reflector 12. The optical engine 11 is mounted on the temple 2c. The optical engine 11 includes a laser module 13, an optical component 14, a movable mirror 15, a laser driver 16, a mirror driver 17, and a controller 18.

[0025] The laser module 13 emits a laser beam. For example, a full-color laser module is used as the laser module 13. The laser module 13 emits a laser beam of a color and light intensity corresponding to the pixels of an image to be projected onto the retina. The laser module 13 will be described in detail later.

[0026] The optical component 14 is a component that optically processes the laser light emitted from the laser module 13. In this embodiment, the optical component 14 includes a collimator lens 14a, a slit 14b, and a neutral density filter 14c. The collimator lens 14a, the slit 14b, and the neutral density filter 14c are arranged in this order along the optical path of the laser light. The optical component 14 may have other configurations.

[0027] The movable mirror 15 is a member for performing scanning with the laser light Ls. The movable mirror 15 is provided in the emission direction of the laser light processed by the optical component 14. The movable mirror 15 is configured to be swingable, for example, around an axis extending in the horizontal direction of the lens 3 and an axis extending in the vertical direction of the lens 3, and reflects the laser light by changing the angle in the horizontal direction and vertical direction of the lens 3. For example, a MEMS (Micro Electro Mechanical Systems) mirror is used as the movable mirror 15.

[0028] The laser driver 16 is a drive circuit that drives the laser module 13. The laser driver 16 drives the laser module 13 based on, for example, the optical power of the laser light and the temperature of the light source unit 20 included in the laser module 13. The mirror driver 17 is a drive circuit that drives the movable mirror 15. The mirror driver 17 swings the movable mirror 15 within a predetermined angle range and at a predetermined timing. The controller 18 is a device that controls the laser driver 16 and the mirror driver 17.

[0029] In the optical engine 11, a laser beam having a color and light intensity corresponding to a pixel of an image to be projected onto the retina is emitted from the laser module 13, passes through the optical component 14, and is reflected by the movable mirror 15. The laser beam reflected by the movable mirror 15 is emitted to the reflector 12 as the laser beam Ls.

[0030] The reflector 12 is a member that reflects the laser light Ls that has passed through the movable mirror 15 and irradiates the retina of a user wearing the near eyewear wearable device 1 with reflected light Lr, thereby projecting an image onto the retina.

[0031] Next, the laser module 13 will be described in detail with reference to Fig. 3 and Fig. 4. Fig. 3 is a plan view of the laser module shown in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. For ease of explanation, the cladding layer 33 is omitted in Fig. 3. As shown in Fig. 3, the laser module 13 includes a light source unit 20 and an optical element 30.

[0032] The light source unit 20 emits visible light. The light source unit 20 includes a red laser diode 21 (first light source) that emits red light, a green laser diode 22 (second light source) that emits green light, and a blue laser diode 23 (third light source) that emits blue light. The peak wavelength of the red light is, for example, in the range of 600 nm to 830 nm. The peak wavelength of the green light is, for example, in the range of 500 nm to 570 nm. The peak wavelength of the blue light is, for example, in the range of 380 nm to 490 nm. The red laser diode 21, the green laser diode 22, and the blue laser diode 23 are arranged in that order in the Y-axis direction.

[0033] In this embodiment, the red laser diode 21 emits red light in the TM fundamental mode (hereinafter referred to as "TM0 mode"). The green laser diode 22 emits green light in the TM0 mode. The blue laser diode 23 emits blue light in the TM0 mode.

[0034] The optical element 30 combines the laser beams emitted from the laser diodes into one laser beam. The optical element 30 is, for example, a planar lightwave circuit (PLC). As shown in FIG. 4, the optical element 30 includes a substrate 31, a core layer 32, and a cladding layer 33.

[0035] The substrate 31 functions as a lower cladding layer. The substrate 31 is made of a material having a lower refractive index than the material of the core layer 32. Examples of materials for the substrate 31 include sapphire, silicon oxide, and silicon on which silicon oxide is laminated. The substrate 31 has a main surface 31a and a back surface 31b on the opposite side to the main surface 31a. The main surface 31a and the back surface 31b are planes defined by the X-axis direction and the Y-axis direction, and intersect with the Z-axis direction (in this embodiment, they are perpendicular). In other words, the X-axis direction and the Y-axis direction are directions along the main surface 31a.

[0036] The cladding layer 33 functions as an upper cladding layer. The cladding layer 33 covers the core layer 32 on the main surface 31a. The cladding layer 33 is provided over the entire main surface 31a. The cladding layer 33 is made of a material having a lower refractive index than the material of the core layer 32. An example of the material of the cladding layer 33 is silicon oxide (e.g., SiO2).

[0037] The core layer 32 is provided on the main surface 31a. The core layer 32 is made of a material having an electro-optic effect. The electro-optic effect is a phenomenon in which the refractive index of a material changes when an electric field is applied to the material. An example of a material for the core layer 32 is lithium niobate (LiNbO3). In this embodiment, the core layer 32 is made of X-cut lithium niobate, and the optical axis (C-axis) of the lithium niobate extends in the Y-axis direction. The core layer 32 includes a mode converter 34R (first mode converter), a mode converter 34G (second mode converter), a mode converter 34B (third mode converter), a modulator 35R (first modulator), a modulator 35G (second modulator), a modulator 35B (third modulator), and a multiplexer 36.

[0038] The mode converter 34R is a mode converter that converts the polarization mode of red light between the TM0 mode and the fundamental TE mode (hereinafter referred to as "TE0 mode"). In this embodiment, the mode converter 34R converts the polarization mode of red light from the TM0 mode (first polarization mode) to the TE0 mode (second polarization mode). The mode converter 34G is a mode converter that converts the polarization mode of green light between the TM0 mode and the TE0 mode. In this embodiment, the mode converter 34G converts the polarization mode of green light from the TM0 mode to the TE0 mode. The mode converter 34B is a mode converter that converts the polarization mode of blue light between the TM0 mode and the TE0 mode. In this embodiment, the mode converter 34B converts the polarization mode of blue light from the TM0 mode to the TE0 mode. The polarization mode is also called a guided mode.

[0039] Each of the mode converters 34R, 34G, and 34B extends in the X-axis direction. The mode converters 34R, 34G, and 34B are arranged in that order in the Y-axis direction. The detailed configuration of each mode converter will be described later.

[0040] The modulator 35R is a modulator that modulates the light intensity of the red light. The modulator 35R is provided after the mode converter 34R, and modulates the light intensity of the red light in the TE0 mode output from the mode converter 34R. The modulator 35G is a modulator that modulates the light intensity of the green light. The modulator 35G is provided after the mode converter 34G, and modulates the light intensity of the green light in the TE0 mode output from the mode converter 34G. The modulator 35B is a modulator that modulates the light intensity of the blue light. The modulator 35B is provided after the mode converter 34B, and modulates the light intensity of the blue light in the TE0 mode output from the mode converter 34B. The detailed configuration of each modulator will be described later.

[0041] The multiplexer 36 multiplexes the red light, the green light, and the blue light. The multiplexer 36 multiplexes the red light emitted from the modulator 35R, the green light emitted from the modulator 35G, and the blue light emitted from the modulator 35B into one laser light, and emits the laser light. The laser light includes a component having a red wavelength (red component), a component having a green wavelength (green component), and a component having a blue wavelength (blue component).

[0042] Next, detailed configurations of the mode converters 34R, 34G, and 34B will be described with further reference to Figs. 5 to 7. Fig. 5 is an enlarged view of a part of the mode converter shown in Fig. 3. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. Fig. 7 is an enlarged view of a part of the mode converter shown in Fig. 3. As shown in Fig. 3, each of the mode converter 34R, the mode converter 34G, and the mode converter 34B includes an end portion 41, a conversion portion 42 (first conversion portion), a connecting portion 43, a conversion portion 44 (second conversion portion), and an end portion 45. The mode converter 34R, the mode converter 34G, and the mode converter 34B have the same configuration, so the configuration of the mode converter 34R will be described here.

[0043] 3 and 5, end 41 is an optical waveguide located at one end (incident end) in the X-axis direction of mode converter 34R. End 41 functions as an incident section. End 41 is provided on main surface 31a and extends in the X-axis direction. Red light in TM0 mode is incident from red laser diode 21 to one end of end 41 in the X-axis direction. End 41 transmits the red light while maintaining the polarization mode of the red light, and emits the red light in TM0 mode to conversion section 42.

[0044] A cross section of the end 41 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The length of the end 41 in the X-axis direction is, for example, 50 μm. The length of the end 41 in the Y-axis direction is substantially constant over the entire length of the end 41 in the X-axis direction. Hereinafter, the length in the Y-axis direction may be referred to as "width". The width of the end 41 is width W0 (first length). Width W0 is, for example, 0.45 μm. The length of the end 41 in the Z-axis direction is substantially constant over the entire length of the end 41 in the X-axis direction. Hereinafter, the length in the Z-axis direction may be referred to as "height". The height of the end 41 is height T0. Height T0 is, for example, 0.7 μm.

[0045] As shown in FIG. 3, FIG. 5, and FIG. 6, the conversion unit 42 is provided between the end 41 and the end 45, and is a part that converts the polarization mode of visible light between the TM0 mode and the TE primary mode (hereinafter referred to as "TE1 mode"). In this embodiment, the conversion unit 42 is provided between the end 41 and the connecting unit 43, and converts the polarization mode of visible light from the TM0 mode to the TE1 mode. The conversion unit 42 is provided on the main surface 31a. The conversion unit 42 has a connection end 42a (first end) and a connection end 42b (second end), which are both ends in the X-axis direction. The connection end 42a is connected to the other end of the end 41 in the X-axis direction. The connection end 42b is connected to one end of the connecting unit 43 in the X-axis direction.

[0046] The conversion unit 42 is divided into a conversion region 42d (first region) and a conversion region 42e (second region) at the intermediate position 42c. The intermediate position 42c is a position between the connection end 42a and the connection end 42b in the X-axis direction. The conversion region 42d is a region of the conversion unit 42 from the connection end 42a to the intermediate position 42c. The conversion region 42e is a region of the conversion unit 42 from the intermediate position 42c to the connection end 42b. The length L11 of the conversion region 42d in the X-axis direction is, for example, 350 μm to 1000 μm. The length L12 of the conversion region 42e in the X-axis direction is, for example, 10 μm to 80 μm. The length L1 of the conversion unit 42 in the X-axis direction is the sum of the length L11 and the length L12, and is, for example, 360 μm to 1010 μm.

[0047] The conversion section 42 includes an upper tapered section 46 and a lower tapered section 47. The upper tapered section 46 and the lower tapered section 47 are stacked in the Z-axis direction. Specifically, the lower tapered section 47 is provided on the main surface 31a, and the upper tapered section 46 is provided on the lower tapered section 47. The height of the upper tapered section 46 is substantially constant over the entire length of the upper tapered section 46 in the X-axis direction. The height of the upper tapered section 46 is height T11. The height T11 is, for example, 0.5 μm. The height of the lower tapered section 47 is substantially constant over the entire length of the lower tapered section 47 in the X-axis direction. The height of the lower tapered section 47 is height T12. The height T12 is, for example, 0.2 μm. The height of the conversion section 42 is the sum of the height of the upper tapered section 46 and the height of the lower tapered section 47, and is height T0.

[0048] In the conversion region 42d, the width of the upper tapered portion 46 increases continuously from width W0 to width Wt (second length) from the connection end 42a to the intermediate position 42c. The width Wt is greater than the width W0. The width Wt is, for example, 0.5 μm to 1.0 μm. The rate of increase in the width of the upper tapered portion 46 in the conversion region 42d may be substantially constant. In the conversion region 42e, the width of the upper tapered portion 46 increases continuously from width Wt to ​​width W1 (fourth length) from the intermediate position 42c to the connection end 42b. The width W1 is greater than the width Wt and smaller than a width Ws described below. The width W1 is, for example, 0.85 μm. The rate of increase in the width of the upper tapered portion 46 in the conversion region 42e may be substantially constant. The upper tapered portion 46 has a shape that is plane-symmetrical with respect to a plane of symmetry SP defined by the X-axis direction and the Z-axis direction.

[0049] In the conversion region 42d, the width of the lower tapered portion 47 increases continuously from width W0 to width Ws (third length) from the connection end 42a to the intermediate position 42c. Width Ws is greater than width Wt. Width Ws is, for example, 1.0 μm to 5.0 μm. The rate of increase in the width of the lower tapered portion 47 in the conversion region 42d may be substantially constant. In the conversion region 42e, the width of the lower tapered portion 47 decreases continuously from width Ws to width W1 from the intermediate position 42c to the connection end 42b. The rate of decrease in the width of the lower tapered portion 47 in the conversion region 42e may be substantially constant. The lower tapered portion 47 has a shape that is plane-symmetrical with respect to the plane of symmetry SP.

[0050] In the conversion section 42 configured as described above, the upper tapered section 46 and the lower tapered section 47 are stacked in the Z-axis direction, so that the conversion section 42 has asymmetry in the Z-axis direction. Here, asymmetry in the Z-axis direction means that two parts separated by a symmetry plane that passes through the center of the conversion section 42 in the Z-axis direction and is perpendicular to the Z-axis direction are not plane-symmetric.

[0051] In the conversion section 42, the effective refractive index of the TM0 mode and the effective refractive index of the TE1 mode approach each other and cross each other as the distance from the connection end 42a increases in the X-axis direction, and thus conversion between the TM0 mode and the TE1 mode is induced. Therefore, when red light in the TM0 mode is incident on the connection end 42a, the polarization mode of the red light is converted from the TM0 mode to the TE1 mode in the conversion section 42. In the conversion region 42d, the width of the lower tapered portion 47 increases more than the width of the upper tapered portion 46 as the distance from the connection end 42a increases. This configuration makes it possible to improve the conversion efficiency while shortening the length of the conversion section 42 in the X-axis direction. In the conversion region 42e, the width of the lower tapered portion 47 decreases as the distance from the connection end 42b increases, and the width of the upper tapered portion 46 and the width of the lower tapered portion 47 become equal at the connection end 42b. This configuration makes it possible to further improve the conversion efficiency.

[0052] For example, about 50% to 60% of the conversion from TM0 mode to TE1 mode occurs in the conversion region 42d, and about 20% to 30% of the conversion from TM0 mode to TE1 mode occurs in the conversion region 42e. Meanwhile, over the entire length in the X-axis direction of the conversion unit 42, the effective refractive index of the TE0 mode is sufficiently different from the effective refractive indexes of the TM0 mode and TE1 mode. Therefore, when red light in the TE0 mode is incident on the connection end 42a, the polarization mode of the red light is maintained in the TE0 mode.

[0053] 3 and 5, the connecting portion 43 is an optical waveguide that connects the conversion portion 42 and the conversion portion 44. The connecting portion 43 is provided on the main surface 31a and extends in the X-axis direction. One end of the connecting portion 43 in the X-axis direction is connected to the connection end 42b, and the other end of the connecting portion 43 in the X-axis direction is connected to the conversion portion 44. Red light in the TE1 mode is incident on the connecting portion 43 from the conversion portion 42. The connecting portion 43 transmits the red light while maintaining the polarization mode of the red light, and outputs the red light in the TE1 mode to the conversion portion 44.

[0054] A cross section of the connecting portion 43 that intersects (is perpendicular to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The length of the connecting portion 43 in the X-axis direction is, for example, 50 μm. The width of the connecting portion 43 is substantially constant over the entire length of the connecting portion 43 in the X-axis direction. The width of the connecting portion 43 is width W1. The height of the connecting portion 43 is substantially constant over the entire length of the connecting portion 43 in the X-axis direction. The height of the connecting portion 43 is height T0.

[0055] As shown in FIG. 3 and FIG. 7, the conversion unit 44 is provided between the end 41 and the end 45, and converts the polarization mode of visible light between the TE0 mode and the TE1 mode. In this embodiment, the conversion unit 44 is provided between the connecting unit 43 and the end 45, and converts the polarization mode of visible light from the TE1 mode to the TE0 mode. The conversion unit 44 is provided on the main surface 31a. The conversion unit 44 has a connection end 44a and a connection end 44b, which are both ends in the X-axis direction. The connection end 44a is connected to the other end of the connecting unit 43 in the X-axis direction. The connection end 44b is connected to one end of the end 45 in the X-axis direction. The conversion unit 44 includes an asymmetric portion 48 (first asymmetric portion), an asymmetric portion 49 (second asymmetric portion), and a connection portion 50.

[0056] The asymmetric portion 48 is an optical waveguide having an asymmetric shape in the Y-axis direction when viewed from the Z-axis direction (in a plan view). The asymmetric portion 48 includes the connection end 44a. The width of the asymmetric portion 48 increases continuously from width W1 (fifth length) to width W2 (sixth length) from the connection end 44a to the connection end 44b. In other words, the width of the asymmetric portion 48 increases continuously from width W1 to width W2 as it moves away from the coupling portion 43. The width W2 is greater than the width W1. The width W2 is, for example, 1.2 μm. The rate of increase in the width of the asymmetric portion 48 may be substantially constant. The height of the asymmetric portion 48 is substantially constant over the entire length of the asymmetric portion 48 in the X-axis direction. The height of the asymmetric portion 48 is height T0. The length L21 of the asymmetric portion 48 in the X-axis direction is, for example, 13 μm to 37 μm.

[0057] The asymmetric portion 48 has a side surface 48a and a side surface 48b which are both side surfaces in the Y-axis direction. The side surface 48a extends in the X-axis direction. The side surface 48b is inclined so as to move away from the side surface 48a as it moves away from the connecting portion 43.

[0058] The asymmetric portion 49 is an optical waveguide having an asymmetric shape in the Y-axis direction when viewed from the Z-axis direction (in a plan view). The asymmetric portion 49 includes the connection end 44b. The width of the asymmetric portion 49 continuously decreases from width W2 to width W3 (seventh length) as it moves away from the coupling portion 43. The width W3 is smaller than the width W2. The width W3 is, for example, 0.4 μm. The rate of decrease in the width of the asymmetric portion 49 may be substantially constant. The height of the asymmetric portion 49 is substantially constant over the entire length of the asymmetric portion 49 in the X-axis direction. The height of the asymmetric portion 49 is height T0. The length L23 of the asymmetric portion 49 in the X-axis direction is, for example, 13 μm to 37 μm.

[0059] The asymmetric portion 49 has a side surface 49a and a side surface 49b which are both side surfaces in the Y-axis direction. The side surface 49a extends in the X-axis direction. The side surface 49b is inclined so as to approach the side surface 49a as it moves away from the connecting portion 43.

[0060] The connecting portion 50 is an optical waveguide provided between the asymmetric portion 48 and the asymmetric portion 49, and connects the asymmetric portion 48 and the asymmetric portion 49. The width of the connecting portion 50 is substantially constant over the entire length of the connecting portion 50 in the X-axis direction. The width of the connecting portion 50 is width W2. The height of the connecting portion 50 is substantially constant over the entire length of the connecting portion 50 in the X-axis direction. The height of the connecting portion 50 is height T0. The length L22 of the connecting portion 50 in the X-axis direction is, for example, 14 μm to 26 μm. The connecting portion 50 has a side surface 50a and a side surface 50b, which are both side surfaces in the Y-axis direction. The side surface 50a and the side surface 50b extend in the X-axis direction and are substantially parallel to each other. The side surface 48a, the side surface 50a, and the side surface 49a are located on the same plane.

[0061] The length L2 of the conversion portion 44 in the X-axis direction is the sum of the lengths L21, L22, and L23, and is, for example, 40 μm to 100 μm. The width of the conversion portion 44 is, for example, 0.4 μm to 1.2 μm.

[0062] In the conversion section 44 configured as above, the asymmetric section 48, the connection section 50, and the asymmetric section 49 are arranged in that order in the X-axis direction, so that the conversion section 44 has asymmetry in the Y-axis direction. Here, the asymmetry in the Y-axis direction means that the two parts separated by the symmetry plane are not plane-symmetric with respect to the symmetry plane that passes through the center of the conversion section 44 in the Y-axis direction and is perpendicular to the Y-axis direction. When red light in the TE1 mode is incident on the connection end 44a, the two components of the TE1 mode that are in opposite phase to each other propagate with different effective optical path lengths, so that different phase changes occur in the two components. The width W1, width W2, width W3, length L21, length L22, and length L23 are set so that the phase matching condition that the two components are in phase is satisfied, so that red light in the TE0 mode is output from the connection end 44b.

[0063] As shown in FIG. 3 and FIG. 7, the end 45 is an optical waveguide located at the other end (output end) in the X-axis direction of the mode converter 34R. The end 45 functions as an output section. The end 45 is provided on the main surface 31a and extends in the X-axis direction. One end of the end 45 in the X-axis direction is connected to the connection end 44b, and the other end of the end 45 in the X-axis direction is connected to the modulator 35R. Red light in the TE0 mode is incident on one end of the end 45 in the X-axis direction from the conversion section 44. The end 45 transmits the red light while maintaining the polarization mode of the red light, and outputs the red light in the TE0 mode to the modulator 35R.

[0064] A cross section of end 45 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The length of end 45 in the X-axis direction is, for example, 50 μm. The width of end 45 is substantially constant over the entire length of end 45 in the X-axis direction. The width of end 45 is width W3. The height of end 45 is substantially constant over the entire length of end 45 in the X-axis direction. The height of end 45 is height T0.

[0065] Next, the detailed configurations of the modulators 35R, 35G, and 35B will be described with reference to Figs. 3, 8, and 9. Fig. 8 is an enlarged view of the modulator shown in Fig. 3. Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 8. As shown in Fig. 3, each of the modulators 35R, 35G, and 35B is a Mach-Zehnder type optical waveguide, and includes an input waveguide 51, a branching section 52, a branching waveguide 53, a branching waveguide 54, a coupling section 55, an output waveguide 56, a signal electrode 57, a grounding electrode 58, a grounding electrode 59, a slab 60 (see Fig. 9), a signal source SS, and a termination resistor TR. The modulators 35R, 35G, and 35B have the same configuration, so the configuration of the modulator 35R will be described here.

[0066] 9, the slab 60 is provided on the main surface 31a. The slab 60 has a flat plate shape. The height of the slab 60 is height T22. The height T22 is, for example, 0.2 μm.

[0067] The input waveguide 51 is an optical waveguide located at one end (incoming end) in the X-axis direction of the modulator 35R. The input waveguide 51 is provided on the slab 60 and extends in the X-axis direction. One end of the input waveguide 51 in the X-axis direction is connected to the other end of the end portion 45 in the X-axis direction. The other end of the input waveguide 51 in the X-axis direction is connected to the branching portion 52.

[0068] A cross section of the input waveguide 51 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The width of the input waveguide 51 is substantially constant over the entire length of the input waveguide 51 in the X-axis direction. The width of the input waveguide 51 is width W3. The height of the input waveguide 51 is substantially constant over the entire length of the input waveguide 51 in the X-axis direction. The height of the input waveguide 51 is height T21. Height T21 is, for example, 0.5 μm.

[0069] The branching unit 52 branches the red light incident from the input waveguide 51 into two red lights. In this embodiment, the branching unit 52 is configured by a multimode interferometer (MMI). The branching unit 52 may be configured by a Y-branching waveguide or a directional coupler. The branching unit 52 outputs the two branched red lights to branching waveguides 53 and 54. The branching unit 52 is provided on a slab 60.

[0070] A cross section of the branching portion 52 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The branching portion 52 has a rectangular shape when viewed from the Z-axis direction. The length of the branching portion 52 in the X-axis direction is, for example, 140 μm. The width of the branching portion 52 is substantially constant over the entire length of the branching portion 52 in the X-axis direction. The width of the branching portion 52 is, for example, 10 μm. The height of the branching portion 52 is substantially constant over the entire length of the branching portion 52 in the X-axis direction. The height of the branching portion 52 is height T21.

[0071] The branching waveguide 53 is an optical waveguide through which one of the red lights branched by the branching section 52 propagates. The branching waveguide 54 is an optical waveguide through which the other of the red lights branched by the branching section 52 propagates. The branching waveguide 53 and the branching waveguide 54 each extend in the X-axis direction from the branching section 52 to the coupling section 55. The branching waveguide 53 and the branching waveguide 54 are provided on the slab 60 and arranged in the Y-axis direction. In the vicinity of the branching section 52, the branching waveguide 53 and the branching waveguide 54 extend so as to move away from each other in the Y-axis direction as they move away from the branching section 52, and in the vicinity of the coupling section 55, they extend so as to move closer to each other in the Y-axis direction as they move closer to the coupling section 55. The branching waveguide 53 and the branching waveguide 54 extend substantially parallel between the vicinity of the branching section 52 and the vicinity of the coupling section 55.

[0072] The cross sections of the branch waveguide 53 and the branch waveguide 54 intersecting (orthogonal to) the X-axis direction have a rectangular shape. The cross sections may have a trapezoidal shape. The length of the branch waveguide 53 in the X-axis direction is, for example, 11 mm. The width of the branch waveguide 53 is substantially constant over the entire length of the branch waveguide 53. The width of the branch waveguide 53 is, for example, 0.7 μm. The height of the branch waveguide 53 is substantially constant over the entire length of the branch waveguide 53. The height of the branch waveguide 53 is height T21. The length of the branch waveguide 54 in the X-axis direction is substantially the same as the length of the branch waveguide 53 in the X-axis direction. The width of the branch waveguide 54 is substantially the same as the width of the branch waveguide 53 and is substantially constant over the entire length of the branch waveguide 54. The height of the branch waveguide 54 is substantially the same as the height of the branch waveguide 53 and is substantially constant over the entire length of the branch waveguide 54.

[0073] The coupling unit 55 couples the red light incident from the branching waveguide 53 and the red light incident from the branching waveguide 54. In this embodiment, the coupling unit 55 is configured by an MMI. The coupling unit 55 may be configured by a Y-branching waveguide or a directional coupler. The coupling unit 55 outputs the coupled red light to an output waveguide 56. The coupling unit 55 is provided on a slab 60.

[0074] A cross section of the joint 55 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The joint 55 has a rectangular shape when viewed from the Z-axis direction. The length of the joint 55 in the X-axis direction is, for example, 140 μm. The width of the joint 55 is substantially constant over the entire length of the joint 55 in the X-axis direction. The width of the joint 55 is, for example, 10 μm. The height of the joint 55 is substantially constant over the entire length of the joint 55 in the X-axis direction. The height of the joint 55 is height T21.

[0075] The output waveguide 56 is an optical waveguide located at the other end (output end) in the X-axis direction of the modulator 35R. The output waveguide 56 is provided on the slab 60 and extends in the X-axis direction. One end of the output waveguide 56 in the X-axis direction is connected to the output end of the coupling unit 55. The other end of the output waveguide 56 in the X-axis direction is connected to the input end of the multiplexer 36.

[0076] A cross section of the output waveguide 56 intersecting (orthogonal to) the X-axis direction has a rectangular shape. The cross section may have a trapezoidal shape. The width of the output waveguide 56 is substantially constant over the entire length of the output waveguide 56 in the X-axis direction. The width of the output waveguide 56 is substantially the same as the width of the branch waveguide 53. The height of the output waveguide 56 is substantially constant over the entire length of the output waveguide 56 in the X-axis direction. The height of the output waveguide 56 is height T21.

[0077] The signal electrode 57, the ground electrode 58, and the ground electrode 59 are electrodes provided on the slab 60 and extend in the X-axis direction. The signal electrode 57 is disposed between the branch waveguide 53 and the branch waveguide 54. The ground electrode 58 and the ground electrode 59 are disposed so as to sandwich the branch waveguide 53 and the branch waveguide 54 in the Y-axis direction. In other words, the ground electrode 58, the branch waveguide 53, the signal electrode 57, the branch waveguide 54, and the ground electrode 59 are disposed in this order at substantially equal intervals in the Y-axis direction. The cladding layer 33 does not cover a part of the signal electrode 57, the ground electrode 58, and the ground electrode 59, and a part of the upper surface of the signal electrode 57, a part of the upper surface of the ground electrode 58, and a part of the upper surface of the ground electrode 59 are exposed.

[0078] The cross sections of the signal electrode 57, the ground electrode 58, and the ground electrode 59 intersecting (orthogonal to) the X-axis direction have a rectangular shape. The length of the signal electrode 57 in the X-axis direction is, for example, 10 mm. The width of the signal electrode 57 is substantially constant over the entire length of the signal electrode 57 in the X-axis direction. The width of the signal electrode 57 is, for example, 5 μm. The height of the signal electrode 57 is substantially constant over the entire length of the signal electrode 57 in the X-axis direction. The height of the signal electrode 57 is height T21.

[0079] The length of the ground electrode 58 in the X-axis direction is, for example, 10 mm. The width of the ground electrode 58 is substantially constant over the entire length of the ground electrode 58 in the X-axis direction. The width of the ground electrode 58 is, for example, 200 μm. The height of the ground electrode 58 is substantially constant over the entire length of the ground electrode 58. The height of the ground electrode 58 is height T21. The length of the ground electrode 59 in the X-axis direction is substantially the same as the length of the ground electrode 58 in the X-axis direction. The width of the ground electrode 59 is substantially the same as the width of the ground electrode 58 and is substantially constant over the entire length of the ground electrode 59 in the X-axis direction. The height of the ground electrode 59 is substantially the same as the height of the ground electrode 58 and is substantially constant over the entire length of the ground electrode 59 in the X-axis direction.

[0080] The signal source SS supplies a modulation signal for modulating the red light propagating through the modulator 35R. One end of the signal source SS is electrically connected to one end of the signal electrode 57, and the other end of the signal source SS is electrically connected to one end of the ground electrode 58 and one end of the ground electrode 59.

[0081] The termination resistor TR electrically terminates the modulated signal. One end of the termination resistor TR is electrically connected to the other end of the signal electrode 57, and the other end of the termination resistor TR is electrically connected to the other end of the ground electrode 58 and the other end of the ground electrode 59.

[0082] In the modulator 35R configured as above, when red light in TE0 mode is incident on the input waveguide 51, it is branched by the branching section 52 into two red lights of the same phase in TE0 mode, and the two red lights are output to the branching waveguides 53 and 54, respectively, and propagate. When a modulation signal is output from the signal source SS to the signal electrode 57, the ground electrode 58, and the ground electrode 59, a potential difference according to the modulation signal is generated between the signal electrode 57 and the ground electrode 58, and between the signal electrode 57 and the ground electrode 59, and a voltage in the Y-axis direction is applied to the branching waveguides 53 and 54. As a result, a phase difference is generated between the red light propagating through the branching waveguide 53 and the red light propagating through the branching waveguide 54.

[0083] Then, the red light propagating through branch waveguide 53 and the red light propagating through branch waveguide 54 are coupled at coupling portion 55. At this time, the optical intensity of the coupled red light varies according to the phase difference between the red light propagating through branch waveguide 53 and the red light propagating through branch waveguide 54. Then, the coupled red light is output to multiplexer 36 via output waveguide 56.

[0084] In the laser module 13 and the optical element 30 described above, the conversion unit 42 converts the polarization mode of visible light between the TM0 mode and the TE1 mode. In the conversion unit 42, the upper tapered portion 46 and the lower tapered portion 47 are stacked in the Z-axis direction, and the conversion unit 42 has asymmetry in the Z-axis direction. In the conversion unit 42, the effective refractive index of the TM0 mode and the effective refractive index of the TE1 mode approach each other as they move away from the connection end 42a, so that conversion between the TM0 mode and the TE1 mode is induced. Therefore, when visible light in the TM0 mode is incident on the connection end 42a of the conversion unit 42, the polarization mode of the visible light is converted from the TM0 mode to the TE1 mode in the conversion unit 42, and then converted from the TE1 mode to the TE0 mode in the conversion unit 44. Therefore, the visible light incident in the TM0 mode can be output in the TE0 mode. As described above, it is possible to convert the polarization mode of the visible light from the TM0 mode to the TE0 mode.

[0085] The length L1 may be 360 ​​μm or more and 1010 μm or less. The width Wt may be 0.5 μm or more and 1.0 μm or less. The width Ws may be 1.0 μm or more and 5.0 μm or less. In this case, the loss of light intensity in the conversion between the TM0 mode and the TE1 mode can be reduced. Therefore, the conversion efficiency between the TM0 mode and the TE1 mode can be improved.

[0086] The conversion unit 44 has asymmetry in the Y-axis direction. When visible light in TE1 mode is incident on the connection end 44a of the conversion unit 44, two components of the TE1 mode that are in opposite phase to each other propagate with different effective optical path lengths. Therefore, these two components undergo different phase changes. The width W1, width W2, width W3, length L21, length L22, and length L23 are set so that a phase matching condition is satisfied under which these two components have the same phase. Therefore, visible light in TE0 mode is output from the connection end 44b of the conversion unit 44. As described above, it is possible to convert the polarization mode of visible light from TE1 mode to TE0 mode.

[0087] The length L2 may be 40 μm or more and 100 μm or less. The width of the conversion section 44 may be 0.4 μm or more and 1.2 μm or less. In this case, the loss of light intensity in the conversion between the TE0 mode and the TE1 mode can be reduced. Therefore, the conversion efficiency between the TE0 mode and the TE1 mode can be improved.

[0088] A configuration is conceivable in which the conversion unit 42 and the conversion unit 44 are connected without using the connecting unit 43 by extending the upper tapered portion 46 of the conversion unit 42. In this configuration, if the width of the upper tapered portion 46 is too wide, unnecessary higher-order modes are generated in visible light, and the conversion efficiency decreases. Therefore, in this configuration, restrictions are imposed on the design of the optical element 30, such as the need to reduce the distance between the conversion unit 42 and the conversion unit 44. On the other hand, in the laser module 13 and the optical element 30, the conversion unit 42 and the conversion unit 44 are connected by the connecting unit 43, and the width of the connecting unit 43 is constant over the entire length of the connecting unit 43 in the X-axis direction. Therefore, by setting the width (width W1) of the connecting unit 43 to a width at which unnecessary higher-order modes are not generated, the distance between the conversion unit 42 and the conversion unit 44 can be adjusted to a desired length. Therefore, the degree of freedom in the design of the optical element 30 can be improved.

[0089] It is known that the electro-optical characteristics of a device made of a material having an electro-optical effect, such as lithium niobate, depend on the direction of voltage application and the direction of polarization of light. For example, when a voltage is applied in the C-axis direction of the material having an electro-optical effect and the direction of the main electric field of light propagating through the device coincides with the C-axis direction, a large electro-optical effect is obtained. In the laser module 13 and the optical element 30, the core layer 32 is made of X-cut lithium niobate, and the C-axis of the lithium niobate extends in the Y-axis direction.

[0090] On the other hand, since the red laser diode 21 emits red light in TM0 mode, the green laser diode 22 emits green light in TM0 mode, and the blue laser diode 23 emits blue light in TM0 mode, the direction of the main electric field of each light is perpendicular to the C-axis direction of the lithium niobate constituting the core layer 32. The mode converters 34R, 34G, and 34B convert the polarization modes of the red light, green light, and blue light from the TM0 mode to the TE0 mode, respectively. As a result, the direction of the main electric field of each light is aligned with the C-axis direction, making it possible to improve the modulation efficiency in the modulators 35R, 35G, and 35B.

[0091] The core layer 32 is made of X-cut lithium niobate, and the C-axis of the lithium niobate extends in the Y-axis direction. Therefore, the multiplexer 36 is designed so that the multiplexing efficiency when multiplexing red light, green light, and blue light in the TE0 mode is higher than the multiplexing efficiency when multiplexing red light, green light, and blue light in the TM0 mode. In the laser module 13 and the optical element 30, the mode converter 34R converts the polarization mode of the red light from the TM0 mode to the TE0 mode, the mode converter 34G converts the polarization mode of the green light from the TM0 mode to the TE0 mode, and the mode converter 34B converts the polarization mode of the blue light from the TM0 mode to the TE0 mode. Therefore, it is possible to improve the multiplexing efficiency in the multiplexer 36.

[0092] In order to output full-color laser light by combining red, green, and blue light, it is necessary to adjust the light intensity of each color of light according to the color to be output. In order to change the light intensity of each color of light in the light source unit 20, a large drive current is required. In the laser module 13 and the optical element 30, the light intensity of the red light is modulated by the modulator 35R, the light intensity of the green light is modulated by the modulator 35G, and the light intensity of the blue light is modulated by the modulator 35B. Therefore, it is possible to output full-color laser light without requiring a large drive current.

[0093] Next, a laser module including an optical element according to another embodiment will be described with reference to Fig. 10. Fig. 10 is a plan view of a laser module including an optical element according to another embodiment. For convenience of explanation, the cladding layer 33 is omitted in Fig. 10. The laser module 13A shown in Fig. 10 differs from the laser module 13 mainly in that it includes an optical element 30A instead of the optical element 30. The optical element 30A differs from the optical element 30 mainly in that it does not include the modulators 35R, 35G, and 35B.

[0094] In the laser module 13A, the configuration common to the laser module 13 provides the same effects as the laser module 13. In the optical element 30A, the configuration common to the optical element 30 provides the same effects as the optical element 30. Since the laser module 13A and the optical element 30A do not include the modulators 35R, 35G, and 35B, it is possible to miniaturize the laser module 13A and the optical element 30A.

[0095] Next, a laser module including an optical element according to yet another embodiment will be described with reference to Fig. 11. Fig. 11 is a plan view of a laser module including an optical element according to yet another embodiment. For convenience of explanation, the cladding layer 33 is omitted in Fig. 11. The laser module 13B shown in Fig. 11 is mainly different from the laser module 13 in that it includes a light source unit 20B and an optical element 30B instead of the light source unit 20 and the optical element 30.

[0096] The light source unit 20B differs from the light source unit 20 mainly in that it includes a red laser diode 21B, a green laser diode 22B, and a blue laser diode 23B instead of the red laser diode 21, the green laser diode 22, and the blue laser diode 23. The red laser diode 21B differs from the red laser diode 21 mainly in the polarization mode of the emitted red light. The red laser diode 21B emits red light in TE0 mode. The green laser diode 22B differs from the green laser diode 22 mainly in the polarization mode of the emitted green light. The green laser diode 22B emits green light in TE0 mode. The blue laser diode 23B differs from the blue laser diode 23 mainly in the polarization mode of the emitted blue light. The blue laser diode 23B emits blue light in TE0 mode.

[0097] The optical element 30B differs from the optical element 30 mainly in the constituent material of the core layer 32 and in that the optical element 30B includes mode converters 61R, 61G, 61B and modulators 62R, 62G, 62B instead of the mode converters 34R, 34G, 34B and modulators 35R, 35G, 35B. In this embodiment, the core layer 32 is made of Z-cut lithium niobate, and the C-axis of the lithium niobate extends in the Z-axis direction.

[0098] The mode converter 61R (first mode converter) converts the polarization mode of red light from TE0 mode (first polarization mode) to TM0 mode (second polarization mode). The mode converter 61G (second mode converter) converts the polarization mode of green light from TE0 mode to TM0 mode. The mode converter 61B (third mode converter) converts the polarization mode of blue light from TE0 mode to TM0 mode. Each of the mode converter 61R, the mode converter 61G, and the mode converter 61B extends in the X-axis direction. The mode converter 61R, the mode converter 61G, and the mode converter 61B are arranged in that order in the Y-axis direction.

[0099] Each of the mode converter 61R, mode converter 61G, and mode converter 61B includes an end 41, a conversion section 42, a connecting section 43, a conversion section 44, and an end 45. Since the mode converter 61R, mode converter 61G, and mode converter 61B have the same configuration, the configuration of the mode converter 61R will be described here. In the mode converter 61R, the end 45, the conversion section 44, the connecting section 43, the conversion section 42, and the end 41 are arranged in this order in the traveling direction of the red light. In other words, the mode converter 61R has a configuration obtained by inverting the mode converter 34R in the X-axis direction.

[0100] End 45 is located at one end (incident end) in the X-axis direction of mode converter 61R, and functions as an incident unit. Red light in TE0 mode is incident from red laser diode 21B to one end in the X-axis direction of end 45. End 45 transmits the red light while maintaining the polarization mode of the red light, and outputs the red light in TE0 mode to conversion unit 44.

[0101] The conversion unit 44 is provided between the end portion 45 and the coupling unit 43, and converts the polarization mode of visible light from the TE0 mode to the TE1 mode. In the conversion unit 44, an asymmetric unit 49, a connection unit 50, and an asymmetric unit 48 are arranged in this order from the end portion 45 toward the coupling unit 43. The connection end 44b is connected to the end portion 45, and the connection end 44a is connected to the coupling unit 43.

[0102] The connecting unit 43 is an optical waveguide that connects the conversion unit 44 and the conversion unit 42. One end of the connecting unit 43 in the X-axis direction is connected to the connection end 44a, and the other end of the connecting unit 43 in the X-axis direction is connected to the connection end 42b. Red light in the TE1 mode is incident on the connecting unit 43 from the conversion unit 44. The connecting unit 43 transmits the red light while maintaining the polarization mode of the red light, and outputs the red light in the TE1 mode to the conversion unit 42.

[0103] The conversion section 42 is provided between the connecting section 43 and the end section 41, and converts the polarization mode of visible light from the TE1 mode to the TM0 mode. The connection end 42b is connected to the connecting section 43, and the connection end 42a is connected to the end section 41. That is, from the connecting section 43 toward the end section 41, the conversion region 42e and the conversion region 42d are arranged in that order.

[0104] End 41 is located at the other end (output end) in the X-axis direction of mode converter 61R, and functions as an output section. Red light in TM0 mode is incident on end 41 from converter 42. End 41 transmits the red light while maintaining the polarization mode of the red light, and outputs the red light in TM0 mode to modulator 62R (first modulator).

[0105] The modulator 62R is a modulator that modulates the light intensity of red light. The modulator 62R is provided after the mode converter 61R, and modulates the light intensity of the red light in TM0 mode emitted from the mode converter 61R. The modulator 62G (second modulator) is a modulator that modulates the light intensity of green light. The modulator 62G is provided after the mode converter 61G, and modulates the light intensity of the green light in TM0 mode emitted from the mode converter 61G. The modulator 62B (third modulator) is a modulator that modulates the light intensity of blue light. The modulator 62B is provided after the mode converter 61B, and modulates the light intensity of the blue light in TM0 mode emitted from the mode converter 61B.

[0106] Modulators 62R, 62G, and 62B differ from modulators 35R, 35G, and 35B primarily in that, instead of signal electrode 57, ground electrode 58, and ground electrode 59, modulators 62R, 62G, and 62B include signal electrode 57B and ground electrode 58B.

[0107] The signal electrode 57B is provided along the branch waveguide 53 and on the branch waveguide 53 via a buffer layer (not shown). The ground electrode 58B is provided along the branch waveguide 54 and on the branch waveguide 54 via a buffer layer (not shown). The cladding layer 33 does not cover the signal electrode 57B and a part of the ground electrode 58B, and a part of the upper surface of the signal electrode 57B and a part of the upper surface of the ground electrode 58B are exposed. One end of the signal source SS is electrically connected to one end of the signal electrode 57B, and the other end of the signal source SS is electrically connected to one end of the ground electrode 58B. One end of the termination resistor TR is electrically connected to the other end of the signal electrode 57B, and the other end of the termination resistor TR is electrically connected to the other end of the ground electrode 58B.

[0108] In the laser module 13B, the configuration common to the laser module 13 provides the same effects as the laser module 13. In the optical element 30B, the configuration common to the optical element 30 provides the same effects as the optical element 30. In the laser module 13B and the optical element 30B, visible light incident in the TE0 mode can be emitted in the TM0 mode. In other words, it is possible to convert the polarization mode of visible light from the TE0 mode to the TM0 mode.

[0109] In the conversion section 44 of this embodiment, the asymmetric section 49, the connection section 50, and the asymmetric section 48 are arranged in that order in the X-axis direction, so that the conversion section 44 has asymmetry in the Y-axis direction. When the red light in the TE0 mode is incident on the connection end 44b, the red light in the TE0 mode propagates with two different effective optical path lengths, and different phase changes occur in the two components. The width W1, the width W2, the width W3, the length L21, the length L22, and the length L23 are set so that the phase matching condition in which the two components are in opposite phase is satisfied, so that the red light in the TE1 mode is output from the connection end 44a. As described above, it is possible to convert the polarization mode of visible light from the TE0 mode to the TE1 mode.

[0110] In the conversion unit 42 of this embodiment, the effective refractive index of the TM0 mode and the effective refractive index of the TE1 mode approach each other as they move away from the connection end 42b in the X-axis direction, so that conversion between the TM0 mode and the TE1 mode is induced. Therefore, when red light in the TE1 mode is incident on the connection end 42b, the polarization mode of the red light is converted from the TE1 mode to the TM0 mode in the conversion unit 42, and the red light in the TM0 mode is output from the connection end 42a. As described above, it is possible to convert the polarization mode of visible light from the TE1 mode to the TM0 mode.

[0111] In the laser module 13B and the optical element 30B, the core layer 32 is made of Z-cut lithium niobate, and the C-axis of the lithium niobate extends in the Z-axis direction. On the other hand, the red laser diode 21B emits red light in TE0 mode, the green laser diode 22B emits green light in TE0 mode, and the blue laser diode 23B emits blue light in TE0 mode, so that the direction of the main electric field of each light is perpendicular to the C-axis direction of the lithium niobate constituting the core layer 32. In response to this, the mode converters 61R, 61G, and 61B convert the polarization modes of the red light, green light, and blue light from the TE0 mode to the TM0 mode, respectively. As a result, the direction of the main electric field of each light is aligned with the C-axis direction, so that it is possible to improve the modulation efficiency in the modulators 62R, 62G, and 62B.

[0112] Furthermore, in the laser module 13B and the optical element 30B, the core layer 32 is made of Z-cut lithium niobate, so that the multiplexer 36 is designed to have a higher multiplexing efficiency when multiplexing red light, green light, and blue light in the TM0 mode than when multiplexing red light, green light, and blue light in the TE0 mode. Therefore, it is possible to improve the multiplexing efficiency in the multiplexer 36.

[0113] Next, a laser module including an optical element according to yet another embodiment will be described with reference to FIG. 12. FIG. 12 is a plan view of a laser module including an optical element according to yet another embodiment. For convenience of explanation, the cladding layer 33 is omitted in FIG. 12. The laser module 13C shown in FIG. 12 is mainly different from the laser module 13B in that it includes an optical element 30C instead of the optical element 30B. The optical element 30C is mainly different from the optical element 30B in that it does not include the modulator 62R, the modulator 62G, and the modulator 62B.

[0114] In the laser module 13C, the configuration common to the laser module 13B provides the same effects as the laser module 13B. In the optical element 30C, the configuration common to the optical element 30B provides the same effects as the optical element 30B. Since the laser module 13C and the optical element 30C do not include the modulators 62R, 62G, and 62B, it is possible to reduce the size of the laser module 13C and the optical element 30C.

[0115] The optical element and laser module according to the present disclosure are not limited to the above-described embodiments.

[0116] For example, the laser modules 13, 13A, 13B, and 13C may be applied to a device other than the near eyewear wearable device 1.

[0117] The optical elements 30, 30A, 30B, and 30C may not include the cladding layer 33. In this case, an air layer may function as an upper cladding layer.

[0118] Each of the optical elements 30, 30A, 30B, and 30C may include one mode converter. In other words, the core layer 32 may include one mode converter that converts the polarization mode of visible light between the TM0 mode and the TE0 mode.

[0119] The mode converters 34R, 34G, 34B, 61R, 61G, and 61B may not include the coupling portion 43. In this case, the connection end 42b is connected to the connection end 44a. This configuration allows the length of the mode converters 34R, 34G, 34B, 61R, 61G, and 61B in the X-axis direction to be shortened. This allows the laser modules 13, 13A, 13B, and 13C and the optical elements 30, 30A, 30B, and 30C to be miniaturized. EXAMPLES

[0120] In the following, the present disclosure will be described in more detail with reference to examples in order to explain the above-mentioned effects, but the present disclosure is not limited to these examples.

[0121] <Evaluation of Conversion Loss in the Conversion Section 42> The conversion loss in the conversion section 42 having the structure of Examples 1 to 12 and Comparative Examples 1 and 2 was calculated. As Examples 1 to 12, a structure in which the upper tapered section 46 and the lower tapered section 47 shown in FIG. 5 were stacked was used. As shown in Table 1, the width W0, width Wt, width Ws, width W1, length L11, and length L12 were set for the wavelength of each color. As Comparative Examples 1 and 2, a structure of only the upper tapered section 46 shown in FIG. 5 was used. As shown in Table 1, in Comparative Examples 1 and 2, the width W0, width Wt (= width Ws), width W1, and length L1 were set for the wavelength of red. In Examples 1 to 12, the height T11 was set to 0.5 μm, and the height T12 was set to 0.2 μm. In Comparative Examples 1 and 2, the height T0 was set to 0.7 μm. The calculation results of the conversion loss are shown in Table 1. [Table 1]

[0122] In Examples 1 to 12, a relatively small loss of about 1.0 dB to 1.7 dB occurred. In Comparative Examples 1 and 2, a loss of more than 10 dB occurred. From these, it can be seen that the conversion loss is suppressed and the conversion efficiency is improved by forming an asymmetric structure in the Z-axis direction in which the upper tapered portion 46 and the lower tapered portion 47 are stacked in the Z-axis direction in the conversion section 42. In Examples 1 to 12, the length L1 was in the range of 360 μm to 1010 μm, the width Wt was in the range of 0.5 μm to 1.0 μm, and the width Ws was in the range of 1.0 μm to 5.0 μm. In this case, it can be seen that the conversion efficiency is improved.

[0123] <Loss evaluation in conversion unit 44> The conversion loss in the conversion section 44 having the structure of Examples 13 to 17 and Comparative Example 3 was calculated. As Examples 13 to 17, a structure in which the asymmetric section 48, the connection section 50, and the asymmetric section 49 shown in FIG. 7 were arranged in the X-axis direction was used. As Comparative Example 3, a structure in which only the asymmetric section 48 and the asymmetric section 49 shown in FIG. 7 were arranged in the X-axis direction and did not include the connection section 50 was used. For the wavelengths of each color, the width W1, the width W2, the width W3, the length L21, the length L22, and the length L23 were set. In Examples 13 to 17 and Comparative Example 3, the height T0 was set to 0.7 μm. The calculation results of the conversion loss are shown in Table 2. [Table 2]

[0124] In Examples 13 to 17, a relatively small loss of about 0.6 dB to 1.0 dB occurred. In Comparative Example 3, a loss of more than 10 dB occurred. From these, it can be seen that by forming an asymmetric structure in the Y-axis direction in which the asymmetric portion 48, the connection portion 50, and the asymmetric portion 49 are arranged in the X-axis direction in the conversion portion 44, the conversion loss is suppressed and the conversion efficiency is improved. In Examples 13 to 17, the length L2 was within a range of 40 μm to 100 μm, and the width of the conversion portion 44 was within a range of 0.4 μm to 1.2 μm. In this case, it can be seen that the conversion efficiency is improved.

[0125] (Additional Note) [Clause 1] A substrate having a major surface; a core layer provided on the main surface and made of a material having an electro-optic effect; Equipped with the core layer includes a mode converter extending in a first direction along the principal surface and converting a polarization mode of visible light between a TM0 mode and a TE0 mode; The mode converter includes: an incident portion that is located at one end of the mode converter in the first direction and into which the visible light of a first polarization mode, which is one of the TM0 mode and the TE0 mode, is incident; an output portion that is located at the other end of the mode converter in the first direction and that outputs the visible light in a second polarization mode that is the other polarization mode of the TM0 mode and the TE0 mode; a first conversion unit provided between the input unit and the output unit, which converts the polarization mode of the visible light between the TM0 mode and the TE1 mode; A second conversion unit provided between the input unit and the output unit, which converts the polarization mode of the visible light between the TE0 mode and the TE1 mode; Equipped with The first conversion portion includes a first end and a second end which are both ends in the first direction, and an upper tapered portion and a lower tapered portion which are stacked in a second direction intersecting the main surface, In a first region from the first end of the first conversion portion to an intermediate position between the first end and the second end, a length of the upper tapered portion in a third direction intersecting the first direction and the second direction increases continuously from the first end to a second length longer than the first length from the first end to the intermediate position, and a length of the lower tapered portion in the third direction increases continuously from the first length to a third length longer than the second length from the first end to the intermediate position, an optical element, in a second region from the intermediate position to the second end of the first conversion section, the length of the upper tapered section in the third direction continuously increases from the second length to a fourth length that is longer than the second length and shorter than the third length from the intermediate position toward the second end, and the length of the lower tapered section in the third direction continuously decreases from the third length to the fourth length from the intermediate position toward the second end.

[0126] [Clause 2] the first polarization mode is the TM0 mode, the second polarization mode is the TE0 mode, the first end is connected to the input portion; Item 2. The optical element described in item 1, wherein the second conversion portion is provided between the first conversion portion and the emission portion.

[0127] [Clause 3] the first polarization mode is the TE0 mode, the second polarization mode is the TM0 mode, the first end is connected to the emission portion, Item 2. The optical element described in item 1, wherein the second conversion portion is provided between the incident portion and the first conversion portion.

[0128] [Article 4] The length of the first conversion portion in the first direction is 360 μm or more and 1010 μm or less, The second length is equal to or greater than 0.5 μm and equal to or less than 1.0 μm, Item 3. The optical element according to any one of items 1 to 3, wherein the third length is not less than 1.0 μm and not more than 5.0 μm.

[0129] [Article 5] The second conversion unit is a first asymmetric portion having an asymmetric shape in the third direction, the length of which in the third direction increases continuously from a fifth length to a sixth length longer than the fifth length as the first asymmetric portion moves away from the first conversion portion; a second asymmetric portion having an asymmetric shape in the third direction, the length of which in the third direction decreases continuously from the sixth length to a seventh length shorter than the sixth length as the second asymmetric portion moves away from the first conversion portion; a connection portion provided between the first asymmetric portion and the second asymmetric portion, the connection portion having a length in the third direction that is the sixth length over the entire length in the first direction; The optical element according to any one of claims 1 to 4, comprising:

[0130] [Article 6] The length of the second conversion portion in the first direction is 40 μm or more and 100 μm or less, Item 6. The optical element of item 5, wherein the length of the second conversion portion in the third direction is not less than 0.4 μm and not more than 1.2 μm.

[0131] [Article 7] 7. The optical element according to claim 1, wherein the mode converter further includes a coupling section coupling the first conversion section and the second conversion section.

[0132] [Article 8] 8. The optical element described in clause 7, wherein the length of the connecting portion in the third direction is constant over the entire length of the connecting portion in the first direction.

[0133] [Article 9] The core layer is a first mode converter that converts a polarization mode of red light from the first polarization mode to the second polarization mode; a second mode converter that converts a polarization mode of green light from the first polarization mode to the second polarization mode; a third mode converter which converts the polarization mode of blue light from the first polarization mode to the second polarization mode; a multiplexer that multiplexes the red light, the green light, and the blue light and emits a laser beam; The optical element according to any one of claims 1 to 8, further comprising:

[0134] [Article 10] The core layer is a first modulator for modulating the light intensity of the red light; a second modulator for modulating the light intensity of the green light; a third modulator that modulates the light intensity of the blue light; 10. The optical element of claim 9, further comprising:

[0135] [Article 11] An optical element according to clause 9 or 10; a first light source that emits the red light in the first polarization mode; a second light source that emits the green light in the first polarization mode; a third light source that emits the blue light in the first polarization mode; A laser module comprising: [Explanation of symbols]

[0136] 13, 13A, 13B, 13C... laser module, 21, 21B... red laser diode (first light source), 22, 22B... green laser diode (second light source), 23, 23B... blue laser diode (third light source), 30, 30A, 30B, 30C... optical element, 31... substrate, 31a... main surface, 32... core layer, 33... cladding layer, 34R, 61R... mode converter (first mode converter), 34G, 61G... mode converter (second mode converter), 34B, 61B... mode converter (third mode converter), 35R, 62R... modulator (first modulation a modulator (second modulator), 35B, 62B...modulator (third modulator), 36...multiplexer, 41...end portion (incoming portion, outgoing portion), 42...conversion portion (first conversion portion), 42a...connecting end (first end), 42b...connecting end (second end), 42c...intermediate position, 42d...conversion region (first region), 42e...conversion region (second region), 43...connecting portion, 44...conversion portion (second conversion portion), 45...end portion (outgoing portion, incoming portion), 46...upper tapered portion, 47...lower tapered portion, 48...asymmetric portion (first asymmetric portion), 49...asymmetric portion (second asymmetric portion), 50...connecting portion.

Claims

1. A substrate having a major surface; a core layer provided on the main surface and made of a material having an electro-optic effect; Equipped with the core layer includes a mode converter extending in a first direction along the principal surface and converting a polarization mode of visible light between a TM0 mode and a TE0 mode; The mode converter includes: an incident portion that is located at one end of the mode converter in the first direction and into which the visible light of a first polarization mode, which is one of the TM0 mode and the TE0 mode, is incident; an output portion that is located at the other end of the mode converter in the first direction and that outputs the visible light in a second polarization mode that is the other polarization mode of the TM0 mode and the TE0 mode; A first conversion unit provided between the input unit and the output unit, which converts a polarization mode of the visible light between the TM0 mode and the TE1 mode; A second conversion unit provided between the incident portion and the exit portion and configured to convert a polarization mode of the visible light between the TE0 mode and the TE1 mode; Equipped with The first conversion portion includes a first end and a second end which are both ends in the first direction, and an upper tapered portion and a lower tapered portion which are stacked in a second direction intersecting the main surface, In a first region from the first end of the first conversion portion to an intermediate position between the first end and the second end, a length of the upper tapered portion in a third direction intersecting the first direction and the second direction continuously increases from the first end to a second length longer than the first length from the first end to the intermediate position, and a length of the lower tapered portion in the third direction continuously increases from the first length to a third length longer than the second length from the first end to the intermediate position, an optical element, in a second region from the intermediate position to the second end of the first conversion portion, a length of the upper tapered portion in the third direction continuously increases from the second length to a fourth length that is longer than the second length and shorter than the third length from the intermediate position toward the second end, and a length of the lower tapered portion in the third direction continuously decreases from the third length to the fourth length from the intermediate position toward the second end.

2. the first polarization mode is the TM0 mode, the second polarization mode is the TE0 mode, the first end is connected to the input portion; The optical element according to claim 1 , wherein the second conversion section is provided between the first conversion section and the emission section.

3. the first polarization mode is the TE0 mode, the second polarization mode is the TM0 mode, the first end is connected to the output portion, The optical element according to claim 1 , wherein the second conversion portion is provided between the entrance portion and the first conversion portion.

4. The length of the first conversion portion in the first direction is 360 μm or more and 1010 μm or less, The second length is equal to or greater than 0.5 μm and equal to or less than 1.0 μm, 4. The optical element according to claim 1, wherein the third length is not less than 1.0 μm and not more than 5.0 μm.

5. The second conversion unit is a first asymmetric portion having an asymmetric shape in the third direction, the first asymmetric portion having a length in the third direction that continuously increases from a fifth length to a sixth length longer than the fifth length as the first asymmetric portion moves away from the first conversion portion; a second asymmetric portion having an asymmetric shape in the third direction, the length of which in the third direction decreases continuously from the sixth length to a seventh length shorter than the sixth length as the second asymmetric portion moves away from the first conversion portion; a connection portion provided between the first asymmetric portion and the second asymmetric portion, the connection portion having a length in the third direction that is the sixth length over the entire length in the first direction; The optical element according to any one of claims 1 to 3, comprising:

6. The length of the second conversion portion in the first direction is 40 μm or more and 100 μm or less, The optical element according to claim 5 , wherein the length of the second conversion portion in the third direction is not less than 0.4 μm and not more than 1.2 μm.

7. 4. The optical element according to claim 1, wherein the mode converter further comprises a coupling section that couples the first conversion section and the second conversion section.

8. The optical element according to claim 7 , wherein the length of the connecting portion in the third direction is constant over the entire length of the connecting portion in the first direction.

9. The core layer is a first mode converter that converts a polarization mode of red light from the first polarization mode to the second polarization mode; a second mode converter that converts a polarization mode of green light from the first polarization mode to the second polarization mode; a third mode converter which converts a polarization mode of blue light from the first polarization mode to the second polarization mode; a multiplexer that multiplexes the red light, the green light, and the blue light and emits a laser beam; The optical element according to any one of claims 1 to 3, further comprising:

10. The core layer is a first modulator for modulating the light intensity of the red light; a second modulator for modulating the light intensity of the green light; a third modulator that modulates the light intensity of the blue light; The optical element according to claim 9 , further comprising:

11. The optical element according to claim 9 ; a first light source that emits the red light in the first polarization mode; a second light source that emits the green light in the first polarization mode; a third light source that emits the blue light in the first polarization mode; A laser module comprising:

12. The optical element according to claim 10; a first light source that emits the red light in the first polarization mode; a second light source that emits the green light in the first polarization mode; a third light source that emits the blue light in the first polarization mode; A laser module comprising:

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