Optical element, smart glasses, optical communication system, computer, and method of manufacturing optical element

Abstract

To provide an optical element obtained by integrating an optical waveguide containing lithium niobate and a silicon substrate.SOLUTION: An optical element is provided, comprising a sapphire substrate having a first optical waveguide and a silicon substrate, the first optical waveguide consisting of a lithium niobate film provided on one surface of the sapphire substrate and being arranged between the silicon substrate and the sapphire substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical element, smart glasses, an optical communication system, a computer, and a method for manufacturing an optical element. [Background technology]

[0002] 2. Description of the Related Art With the spread of the Internet, communication traffic has increased dramatically, and in recent years, optical communication systems are being required to have the ability to process large amounts of data at high speeds.

[0003] In such optical communication systems, laser diodes and photodiodes are connected using optical waveguides. As a typical example of an optical waveguide, Patent Document 1 discloses an optical waveguide made from a c-axis oriented LiNbO3 thin film formed by sputtering on a sapphire substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-131936 Summary of the Invention [Problem to be solved by the invention]

[0005] However, optical waveguides used in optical communication systems also include those mounted on substrates other than sapphire. To realize an optical communication system, optical waveguides must be connected to one another, such as an optical waveguide made of lithium niobate film on a sapphire substrate (LN waveguide) and an optical waveguide mounted on another substrate. In this case, it was common to connect an LN optical waveguide in the shape of a device to a sapphire substrate by arranging an optical waveguide in the shape of a device mounted on another substrate. However, because chips with two optical waveguides mounted on almost the same plane must be mounted side by side, the chips, which consist of multiple optical waveguides, inevitably become larger.

[0006] Furthermore, to control electro-optical elements such as LN optical modulators containing lithium niobate films, it is necessary to electrically connect a chip containing electrical circuits to an LN optical waveguide on a sapphire substrate. However, even in this case, the chip containing the electrical circuits and the chip-shaped LN optical waveguide must be mounted side-by-side on almost the same plane, which inevitably increases the size of the entire chip, including the electrical circuits and the LN optical waveguide.

[0007] The present disclosure aims to provide an optical element including an LN optical waveguide provided on a sapphire substrate and a substrate other than the sapphire substrate, while avoiding the increase in chip size that has been made in consideration of the above circumstances, as well as smart glasses, optical communication systems, computers, and methods for manufacturing the optical element that use the optical element. [Means for solving the problem]

[0008] To solve the above problems, the present disclosure provides the following means.

[0009] An optical element according to one aspect of the present disclosure is an optical element including a sapphire substrate having a first optical waveguide, and a silicon substrate, wherein the first optical waveguide is made of a lithium niobate film provided on one surface of the sapphire substrate, and the first optical waveguide is sandwiched between the silicon substrate and the sapphire substrate.

[0010] An optical communication system according to one aspect of the present disclosure is characterized by using an optical element according to the present disclosure.

[0011] A smart glass according to one aspect of the present disclosure is characterized by using an optical element according to the present disclosure.

[0012] A computer according to one aspect of the present disclosure comprises a PIC including an optical element according to the present disclosure, optical wiring, a plurality of GPUs, and a CPU, wherein the PIC is provided in the GPU and the CPU, and the PIC is connected to the plurality of GPUs or the GPU and the CPU via the optical wiring.

[0013] A manufacturing method of an optical element according to one aspect of the present disclosure is a manufacturing method of an optical element including a sapphire substrate and a substrate different from the sapphire substrate, the manufacturing method including: a first substrate patterning step of forming a first optical waveguide on one surface of the sapphire substrate and creating a first pattern; The method includes a second substrate patterning step of patterning a substrate different from the sapphire substrate to form a second pattern on one surface of the substrate different from the sapphire substrate, a wafer bonding step of bonding one surface of the sapphire substrate on which the first pattern has been formed in the first substrate patterning step to one surface of the silicon substrate on which the second pattern has been formed in the second substrate patterning step, and a dicing step of dicing the sapphire substrate and the substrate different from the sapphire substrate that have been integrated in the wafer bonding step. [Effects of the Invention]

[0014] The optical element according to the present disclosure makes it possible to avoid an increase in chip size and to provide an optical element including an LN optical waveguide provided on a sapphire substrate and a substrate different from the sapphire substrate. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of an optical element according to a first embodiment. [Figure 2] FIG. 1 is a cross-sectional view of an optical element according to a first embodiment. [Figure 3] FIG. 1 is a cross-sectional view of an optical element according to a first embodiment. [Figure 4] FIG. 10 is a perspective view of an optical element according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view of an optical element according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view of an optical element according to a second embodiment. [Figure 7] FIG. 10 is a perspective view of an optical element according to a third embodiment. [Figure 8] FIG. 10 is a cross-sectional view of an optical element according to a third embodiment. [Figure 9]2 is a flowchart of a manufacturing method according to the present embodiment. [Figure 10] 3A to 3C are detailed views of the method for manufacturing the optical element according to the first embodiment. [Figure 11] 3A to 3C are detailed views of the method for manufacturing the optical element according to the first embodiment. [Figure 12] 3A to 3C are detailed views of the method for manufacturing the optical element according to the first embodiment. [Figure 13] 10A to 10C are detailed views of the method for manufacturing the optical element according to the second embodiment. [Figure 14] 10A to 10C are detailed views of the method for manufacturing the optical element according to the third embodiment. [Figure 15] FIG. 10 is a diagram of an optical element with a light source, in which a laser diode is attached to the optical element of this embodiment. [Figure 16] FIG. 1 is a diagram illustrating an optical communication system using the optical element of the present embodiment. [Figure 17] FIG. 1 is a diagram of smart glasses using the optical element of this embodiment. [Figure 18] FIG. 10 is a diagram of a computer using the optical element of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0017] First, let's define the directions. One direction on the wafer surface is the X direction. The normal direction to the wafer surface is the Y direction, and the direction perpendicular to the X direction within the wafer surface is the Z direction. Here, we assume that thin films are stacked in the Y direction, and light is guided in the Z direction.

[0018] "First embodiment" 1 is a perspective view of an optical element 101 according to the first embodiment. The optical element 101 is fabricated by bonding a patterned silicon substrate 11 (a substrate different from a sapphire substrate) and a patterned sapphire substrate 21 together as wafers, followed by dicing.

[0019] The following describes the configuration of the silicon substrate side of optical element 101. The silicon substrate side is composed of silicon substrate 11, core layer 12a patterned on one surface of the silicon substrate, cladding layer 13 (Si cladding layer) in which patterned core layer 12a is embedded, and through electrode 14a (Si through electrode) on the silicon substrate side. Here, core layer 12a, together with silicon substrate 11 and Si cladding layer 13, forms an optical waveguide (Si optical waveguide).

[0020] Materials for the core layer 12a include silicon films (Si films) such as polysilicon and SiNx (silicon nitride) films. Examples of Si clad layers include SiO2 (silicon oxide) films. If the refractive index of the core layer 12a is designed to be larger than the refractive indexes of the silicon substrate 11 and the clad layer 13, the form of the Si optical waveguide is not limited to an embedded type optical waveguide, and various types of waveguides can be appropriately adopted, such as a method in which a convex shape is created on the silicon substrate and the light is confined by the surrounding air, or a method in which a strip-shaped Si film or SiNx film is placed on the top surface of the Si clad layer and an air space is created around it to confine the light.

[0021] The Si through electrode 14a is an electrode that penetrates a silicon substrate, and is formed using a so-called TSV (through-silicon via) mounting technique.

[0022] Next, we will explain the configuration of the sapphire substrate side of optical element 101. It consists of sapphire substrate 21, c-axis oriented lithium niobate epitaxial film 22 (LN thin film) provided on one surface of the sapphire substrate, LN ridge portions 24a, 24b, and 24c obtained by processing the LN thin film by etching or the like, cladding layer 23 (LN cladding layer) covering the side surfaces of the LN ridge portion, buffer layer 25 (LN buffer layer) provided on the surface of the LN ridge portion opposite the sapphire substrate side, and LN-side electrode 26 (LN electrode).

[0023] The LN thin film 22 is an epitaxial film grown epitaxially on the sapphire substrate 21. An epitaxial film is a single-crystal film whose crystal orientation is aligned with the underlying substrate. An epitaxial film is a film with a single crystal orientation in the Y direction and in the XZ in-plane direction, with the crystals aligned in the X-axis, Y-axis, and Z-axis directions. Whether the film formed on the sapphire substrate 21 is an epitaxial film can be verified, for example, by checking the peak intensity and poles at the orientation positions in 2θ-θ X-ray diffraction.

[0024] The thickness of the LN thin film 22 is, for example, 2 μm or less. The thickness of the lithium niobate film 22 refers to the thickness of the portion other than the LN ridge portion. If the lithium niobate film 40 is too thick, there is a risk of the crystallinity being reduced. The thickness of the lithium niobate film 40 is, for example, at least about 1 / 10 of the wavelength of the light used.

[0025] The LN cladding layer 23 covers and protects the side surfaces of the LN ridge portion and is made of SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, or a mixture thereof.

[0026] The LN buffer layer 25 covers and protects the underside of the LN ridge portion and is made of SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, or a mixture thereof.

[0027] The LN ridge portions 24a, 24b, and 24c form a ridge-type optical waveguide (LN optical waveguide) together with the surrounding LN thin film 22, LN cladding layer 23, and LN buffer layer 25. If the LN ridge portion has a higher refractive index than its surroundings, it can be configured not only as an embedded type in the cladding layer or LN buffer layer, but also as a method in which air is placed around the LN ridge portion to confine and guide the light.

[0028] LN ridge portion 24a is connected to LN ridge portions 24b and 24c via branch portions, and LN ridge portions 24a, 24b, and 24c form a Mach-Zehnder interferometer optical waveguide (MZI optical waveguide) 24 consisting of LN optical waveguides. LN electrode 26 applies an electric field to each of the branched guided light propagating through LN ridge portion 24b and LN ridge portion 24c. Because lithium niobate has an electro-optic effect, the phase of the guided light changes in response to the applied electric field. When the branched guided light is combined, modulated light whose optical phase is controlled by the electric field can be obtained. In other words, the MZI optical waveguide 24 and LN electrode 26 enable an optical element having the function of an LN optical modulator to be integrated into the sapphire substrate 11.

[0029] A part of the LN electrode 26 includes a through electrode 26a (LN through electrode) formed by filling a through hole provided in the sapphire substrate with metal.

[0030] Figure 2 is a cross-sectional view of the XY plane taken at point A1 in Figure 1, viewed from the Z direction, the direction of light travel. The Si optical waveguide 12a is formed from a core layer and is surrounded by a silicon substrate 11 and a cladding layer 13. Looking in the Y direction, which is the lamination layer, an LN buffer layer 25 of LN is located on the silicon side of the optical waveguide 12a, and an LN ridge portion 24a is located on the LN buffer layer. An LN thin film 22 is located on the LN ridge portion 24a, and a sapphire substrate is located on top of that.

[0031] The light guided through the Si optical waveguide 12a and the light guided through the MZI optical waveguide 24 can be coupled by selecting the film thickness and materials of the Si cladding layer 13, the LN buffer layer 25, etc. In other words, the Si optical waveguide and the MZI optical waveguide can be optically connected. Alternatively, each light can be propagated independently.

[0032] 3 is a cross-sectional view of the XY plane taken at point B1 in FIG. 1, viewed from the Z direction, the direction of light propagation. Silicon-side optical waveguide 12a is formed from a core layer and is surrounded by silicon substrate 11 and cladding layer 13. LN-side electrode 26b is disposed on silicon-side electrode 14b. LN-side electrode 26c is disposed on silicon-substrate-side electrode 14c. LN buffer layer 25 is disposed on LN-side electrodes 26a and 26b, and LN ridge portions 24b and 24c are disposed on the LN buffer layer. Cladding layer 23 surrounds LN ridge portions 24b and 24c. An LN thin film 22 is disposed on the LN ridge portion, and a sapphire substrate 21 is disposed on LN thin film 22.

[0033] The LN through electrode 26a is connected to the top surface of the sapphire substrate through a through hole. Furthermore, by applying a voltage to the LN-side electrode 26b as a signal electrode (LN signal electrode) and the LN-side electrode 26c as a ground electrode (LN ground electrode), electric fields in opposite directions can be applied to the light guided through the LN ridge portion 24b and the LN ridge portion 24c. Because the LN thin film is a c-axis-oriented sputtered film, TM mode light, whose polarization direction is parallel to the c-axis, is guided. By applying electric fields in opposite directions to the guided TM mode light, the signs of the phase shifts of the light guided through the LN ridge portion 24b (first arm) that becomes the first arm and the LN ridge portion 24c (second arm) that becomes the second arm are reversed. This enables on / off control of the combined light in response to the on / off control of the electric field, enabling operation as an optical modulator.

[0034] The silicon substrate 11 and the sapphire substrate 12 may be bonded by surface activated bonding, atomic diffusion bonding, or resin. Any method is acceptable as long as bonding is possible. Depending on the selected method, an altered layer or resin layer may be added to the bonding surfaces, but this is not shown in the drawings.

[0035] The above is an explanation of the optical element 101 according to the first embodiment. The optical element 101 has an LN optical waveguide, which serves as the first optical waveguide, sandwiched between a silicon substrate 11 and a sapphire substrate 21. The optical element 101 can realize an optical element that combines silicon photonics and an LN thin film, and can be mass-produced at the wafer level through a packaging process.

[0036] "Second embodiment" Next, an optical element 102 according to the second embodiment will be described. Fig. 4 is a perspective view of the optical element 102 according to the second embodiment. Explanations of the same parts as those in the first embodiment will be omitted.

[0037] We will now describe the configuration of the silicon substrate side of the optical element 102. The silicon substrate side includes a silicon substrate 11, a cladding layer 13 (Si cladding layer) provided on the silicon substrate, a through electrode 14a (Si through electrode) on the silicon substrate side, and a ground electrode 14c (Si ground electrode).

[0038] Figure 5 is a cross-sectional view of the XY plane taken at point A2 in Figure 4, viewed from the Z direction, the direction of light propagation. A Si clad layer 13 is located on a silicon substrate 11. Looking in the Y direction, which is the lamination layer, an LN buffer layer 25 is located on the Si clad layer, and an LN ridge portion 24a is located on the LN buffer layer. An LN thin film 22 is located on the LN ridge portion 24a, and a sapphire substrate is located on that.

[0039] 6 is a cross-sectional view of the XY plane taken along the line B2 in FIG. 4, seen from the Z direction, the direction of light propagation. An Si cladding layer 13 is disposed on a silicon substrate 11. A silicon-side signal electrode 14b (Si signal electrode) and a silicon-side ground electrode 14c (Si ground electrode) are provided on the surface of the Si cladding layer 13. An LN-side electrode 26b is disposed on the Si signal electrode 14b, and an LN ground electrode 26c is disposed on the Si ground electrode 14c. An LN buffer layer 25 is disposed on the LN signal electrode 26b and the LN ground electrode 26c, and LN ridge portions 24b and 24c are disposed on the LN buffer layer. A cladding layer 23 surrounds the LN ridge portions 24b and 24c. An LN thin film 22 is disposed on the LN ridge portion, and a sapphire substrate 21 is disposed on the LN thin film 22.

[0040] Here, the silicon substrate 11, the Si cladding layer 13, the Si signal electrode 14b, and the Si ground electrode 14c constitute a CMOS circuit 15a (electrical circuit) including a transistor, and the Si through electrode 14a serves as a ground electrode connecting the Si ground electrode 14c to the outside via a through hole in the silicon substrate.

[0041] Although not shown, the impurity concentration on the surface of the Si substrate may be adjusted by ion implantation or the like, and a wiring layer constituting a CMOS circuit may be formed inside the Si cladding layer.

[0042] The silicon substrate 11 and the sapphire substrate 12 may be bonded by surface activated bonding, atomic diffusion bonding, or by using resin. Any bonding method is acceptable. By performing wafer bonding, the Si signal electrode 14b is electrically connected to the LN signal electrode 26b, and the Si ground electrode is electrically connected to the LN ground electrode 26c.

[0043] For example, the CMOS circuit 15a serves as a driver circuit for the LN modulator, and a high-frequency electrical signal propagates to the first arm 24b via the Si signal electrode 14b, which serves as the signal electrode of the CMOS circuit, thereby enabling high-speed modulated waveguide light to be obtained.

[0044] The above is a description of the optical element 102 according to the second embodiment, and the optical element 102 can be actively operated by applying an electric field to the LN optical waveguide that serves as the first optical waveguide.

[0045] "Third embodiment" 7 is a perspective view of an optical element 103 according to the third embodiment. Descriptions of the same parts as those in the first and second embodiments will be omitted.

[0046] The optical element 103 has a configuration in which the Si optical waveguide 12a of the first embodiment and the CMOS circuit 15a of the second embodiment are both included on the silicon substrate side. The cross section of the XY plane at point A3 as viewed from the Z direction, the light propagation direction, is the same as that of the first embodiment.

[0047] Fig. 8 is a cross-sectional view of the XY plane as seen from the Z direction, the light traveling direction, at point B3 in Fig. 8. A Si cladding layer 13 is provided with a Si optical waveguide 12a and a CMOS circuit 15a including a transistor.

[0048] Although an example has been shown in which the silicon-side optical waveguide 12a and the CMOS circuit 15a are arranged in the same XY plane, wiring may be routed in the XZ plane and connected to the LN-side electrodes 26a, 26b. The silicon-side optical waveguide 12a and the CMOS circuit 15a may be arranged in positions where the optical characteristics of the silicon-side optical waveguide 12a and the electrical characteristics of the CMOS circuit 15a do not affect each other.

[0049] Although an example has been shown in which the silicon-side optical waveguide 12a and the CMOS circuit 15a are arranged in the same XY plane, wiring may be routed in the XZ plane and connected to the LN-side electrodes 26a, 26b. The silicon-side optical waveguide 12a and the CMOS circuit 15a may be arranged in positions where the optical characteristics of the silicon-side optical waveguide 12a and the electrical characteristics of the CMOS circuit 15a do not affect each other.

[0050] The above is a description of the optical element 103 according to the third embodiment. The optical element 103 has both an LN optical waveguide as the first optical waveguide and a Si optical waveguide as the second optical waveguide, and therefore can be actively operated by applying an electric field, and can further utilize the relationship between light guided through the LN optical waveguide and light guided through the Si optical waveguide.

[0051] "Embodiments of a manufacturing method for an optical element" Next, an embodiment of a method for manufacturing an optical element will be described. Figure 9 is a flowchart of a method for manufacturing an optical element 101. The method comprises a silicon substrate patterning step (first substrate patterning step) S1, a sapphire substrate patterning step (second substrate patterning step) S2, a wafer bonding step S3, and a dicing step S4. The silicon substrate patterning step S1 and the sapphire substrate patterning step S2 can be performed in any order. In the wafer bonding step S3, the patterned silicon substrate and the patterned sapphire substrate are wafer-bonded, and then in the dicing step, the wafer-bonded substrates are diced to cut out the optical elements.

[0052] 10 to 12 will explain in detail a manufacturing method of an optical element 101 having an optical waveguide on the silicon substrate side and an LN optical modulator on the sapphire substrate side. Fig. 10 shows a silicon substrate patterning step S1 and a sapphire substrate patterning step S2.

[0053] In the silicon substrate patterning process S1, first, a silicon substrate 11, which is a substrate different from a sapphire substrate, is prepared in the silicon substrate preparation process S11. Then, a polysilicon film or a silicon nitride (SiNx) film is deposited in the core layer formation process S12. Then, in the silicon-side optical waveguide formation process S13, a waveguide pattern is formed by photolithography and etching to form an optical waveguide. After the waveguide pattern is formed, silicon oxide (SiO2) is deposited to form an optical waveguide (Si optical waveguide) with the embedded core layer 12a as its core, resulting in a patterned silicon substrate.

[0054] In the sapphire substrate patterning process S2, first, a sapphire substrate 11 is prepared in a sapphire substrate preparation process S21. Then, in an LN film layer formation process S22, a c-axis oriented LiNbO3 film is deposited by sputtering. Then, in an LN optical waveguide formation process S23, an optical waveguide pattern is photolithographically formed on the LN thin film, followed by milling or etching to form LN ridge portions 24a, 24b, and 24c. An insulating cladding layer 23 (LN cladding layer) is then deposited around the LN ridge portion. Then, in an LN electrode formation process S24, an LN buffer layer is deposited, and an electrode pattern for the LN electrode is created by photolithography, electrode vapor deposition, lift-off, etching, or the like. In this manner, a patterned sapphire substrate is obtained.

[0055] 11, the wafer bonding process 3 will be described in detail. In the patterned substrate preparation process S31, a patterned silicon substrate produced in the silicon substrate patterning process and a patterned sapphire substrate produced in the sapphire substrate patterning process are prepared. Then, in the patterned substrate face-to-face alignment process 32, the patterned surfaces of the silicon substrate 11 and the sapphire substrate 21 are aligned so that they face each other. Then, in the patterned substrate bonding process S33, the silicon substrate 11 and the sapphire substrate 21 are bonded together. Examples of wafer bonding methods include surface activated bonding, atomic diffusion bonding, and resin bonding. Then, in the composite substrate polishing process, the integrated composite substrate is polished from the bottom surface of the silicon substrate and the top surface of the sapphire substrate. 12, after the composite substrate polishing step, through holes are formed in the underside of the silicon substrate in a through electrode fabrication step S35, and metal is embedded in the fabricated through holes to form through electrodes. Thereafter, in a dicing step S4, the composite substrate is diced to cut into element sizes, thereby obtaining optical elements 101.

[0056] FIG. 13 illustrates in detail a manufacturing method for an optical element 102 having a CMOS circuit including a transistor on a silicon substrate and a LiNbO3 optical modulator on a sapphire substrate. Explanations of previously described steps are omitted. In the silicon substrate patterning step (first substrate patterning step), a silicon substrate preparation step S11 is followed by a transistor formation step S14. In the transistor formation step, ion implantation and thermal diffusion are performed on the silicon substrate 11 to adjust the impurity concentration near the Si substrate surface, an insulating clad layer 12 and electrodes serving as wiring layers are fabricated within the clad layer, and silicon-side electrodes connected to the LN-side electrodes are formed to form a CMOS circuit 15a including a transistor. The patterned silicon substrate having the transistor and the patterned sapphire substrate are then bonded in a wafer bonding step 3. The composite substrate is then diced into element sizes in a dicing step S4, yielding the optical element 102.

[0057] FIG. 14 illustrates in detail a manufacturing method for an optical element 103 having a transistor and an optical waveguide on a silicon substrate and an LN optical modulator on a sapphire substrate. Explanations of previously described steps are omitted. In the silicon substrate patterning process, after the silicon substrate preparation process S11, a transistor formation process S14 is performed to form a CMOS circuit 15a, followed by the silicon-side optical waveguide formation process S13. In the silicon-side optical waveguide formation process, a core layer 12a such as a silicon film or SiNx film is formed, a waveguide pattern is formed by photolithography or etching, and the periphery of the waveguide pattern is buried with a cladding layer. A material with a lower refractive index than the core layer, such as SiO2, can be appropriately selected for the cladding layer. Subsequently, in the wafer bonding process 3, the patterned silicon substrate and the patterned sapphire substrate are bonded together. Then, in the dicing process S4, the composite substrate is diced to cut into element size, yielding the optical element 102.

[0058] The above example describes a method for manufacturing an optical element by forming lithium niobate on a sapphire substrate to form a composite substrate. It is also possible to manufacture optical elements by forming lithium niobate on a silicon substrate instead of a sapphire substrate. In this case, to form a lithium niobate element on a silicon substrate, bulk lithium niobate must be attached to the silicon substrate and then used to fabricate the element. However, bulk lithium niobate must be formed to the same size as the silicon substrate, and a lithium niobate film of the typical 12-inch size cannot be formed on a silicon substrate. Therefore, the limit for combining a lithium niobate element with an optical waveguide formed on a silicon substrate is approximately 6 inches. Therefore, optical elements can be obtained by processing wafers of 6 inches or larger.

[0059] "Embodiment of Optical Element with Laser Diode" Next, as another application example, an optical element 201 equipped with a laser diode (optical element with a laser diode) will be described. An embodiment of an optical element with a laser diode in which a laser diode is connected to the Si optical waveguide 12a or the input portion 24a of the LN optical waveguide of the optical element 103 will be described.

[0060] Figure 15 is a diagram of the XZ plane of an optical element with a laser diode, in which a laser diode is attached to optical element 103, and the LN optical waveguide on the sapphire substrate side of optical element 103 is viewed from the XZ plane. The sapphire substrate is provided with three sets of MZI optical waveguides that guide light with visible wavelengths of 400 nm to 700 nm, a multiplexer that multiplexes the MZI optical waveguides into a single LN optical waveguide, and three sets of LN signal electrodes and LN ground electrodes. The output sections of the MZI optical waveguides are multiplexed by the multiplexer.

[0061] The MZI optical waveguides 24ar, 24br, and 24cr correspond to red, the MZI optical waveguides 24ag, 24bg, and 24cg correspond to green, and the MZI optical waveguides 24ab, 24bb, and 24cb correspond to blue. Three pairs of LN signal electrodes 26b and LN ground electrodes 26c are provided on the sapphire substrate. The LN signal electrode 26bb and LN ground electrode 26cb corresponding to blue are shown here. The output sections of each MZI optical waveguide are combined by a combiner 24d.

[0062] An optical semiconductor element 41r emitting red light, an optical semiconductor element 41g emitting green light, and an optical semiconductor element 41b emitting blue light are connected to the input terminals of each of the three sets of MZI optical waveguides. Furthermore, the light of the red, green, and blue wavelengths is modulated by three sets of LN electrodes. In this way, the use of optical element 103 in an optical element with a laser diode allows for a compact size. Furthermore, since the LN modulator controls the highly insulating external modulator with voltage, almost no current is required for intensity modulation, and it operates with the minimum current required for laser emission, enabling low power consumption.

[0063] Each optical semiconductor element is mounted on a subcarrier (base) 42, and the MZI optical waveguide is sandwiched between a sapphire substrate and a silicon substrate.

[0064] Various laser elements can be used as the optical semiconductor element. For example, commercially available laser diodes (LDs) that emit red, green, or blue light can be used. For red light, light with a peak wavelength of 610 nm or more and 750 nm or less can be used. For green light, light with a peak wavelength of 500 nm or more and 560 nm or less can be used. For blue light, light with a peak wavelength of 435 nm or more and 480 nm or less can be used.

[0065] In the optical element with a laser diode, the three optical semiconductor elements are designated as LD 41b that emits blue light, LD 41g that emits green light, and LD 41r that emits red light, and are arranged at intervals in a direction substantially perpendicular to the emission direction of the light emitted from each LD.

[0066] The LD is mounted as a bare chip on a subcarrier 42, which can be configured by directly bonding a composite substrate of a sapphire substrate and a silicon substrate via a metal layer. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling.

[0067] In the laser diode-equipped optical element 201, an antireflection film 51 is provided between the LD and the light incident surface of the light input unit 24a. For example, the antireflection film is integrally formed on the side surface of the sapphire substrate, the LD, and the light incident surface of the light input unit 24a. However, the antireflection film may be formed only on the light incident surface of the LN optical waveguide light input unit 24a.

[0068] The anti-reflection film 51 is a film that prevents reflection in the direction opposite to the direction of incidence from the light incident surface of the light input unit 24a and increases the transmittance of incident light. The anti-reflection film is a multilayer film formed by alternately stacking, for example, multiple types of dielectrics at predetermined thicknesses according to the wavelengths of the incident light, i.e., red light, green light, and blue light. Examples of the aforementioned dielectrics include titanium oxide (TiO2), tantalum oxide (Ta2O5), silicon oxide (SiO2), and aluminum oxide (Al2O3).

[0069] The output surface of the LD and the light incident surface of the LN light input unit 24a are arranged with a predetermined gap between them. The light incident surface of the LN light input unit 24a faces the output surface of the LD, and there is a gap between the LD output surface and the light incident surface of the LN optical waveguide in the Z direction. Because the optical element with a laser diode is exposed to air, the gap is filled with air. Because the gap is filled with the same gas (air), it is easy to make each color light emitted from the LD enter the incident path while satisfying a predetermined coupling efficiency. When the optical element with a laser is used in AR glasses or VR glasses, taking into account the light intensity required for the AR glasses or VR glasses, the size of the gap (spacing) in the Z direction is, for example, greater than 0 μm and less than 5 μm.

[0070] Although the above describes an example of an optical element with a laser diode in which a visible light laser diode is connected to an LN optical waveguide, it may also be connected to a Si optical waveguide.Furthermore, if the LN optical waveguide or Si optical waveguide is configured to allow near-infrared light of 800 nm to 1600 nm to propagate, a laser diode that emits near-infrared light of 800 nm to 1600 nm may be connected.

[0071] In this way, by attaching a laser diode to the optical element according to the present disclosure, it is possible to realize miniaturization of a visible light source device that emits visible light or a near-infrared light source device that emits near-infrared light.

[0072] "Embodiment of Optical Communication System" Next, as another application example, an embodiment of an optical communication system using the optical element according to the present disclosure will be described. An optical communication system 7001 shown in FIG.

[0073] The light source unit 6001 includes a laser diode 6030 for an optical communication system, an optical modulation element 6200 for an optical communication system, an electric signal generation element 6013, and a signal emission port 6014. The laser diode 6030 for an optical communication system includes an optical element 201 with a laser diode.

[0074] The receiving unit includes a signal inlet 6024 , a visible light signal receiving section 6021 , and an optical-electrical signal conversion element 6022 .

[0075] The speed at which visible light signals are generated can be increased when visible light is used as the light emitted from light source unit 6001. With the increase in computer processing speed and the accompanying improvement in information data processing capabilities, further increases in communication speed are desired in optical communication systems, but in a transmitting device that generates visible light signals by internal modulation, there is a limit to how much the on / off switching time of the visible light source can be reduced, making it difficult to increase the speed at which visible light signals are generated.

[0076] Furthermore, when visible light sources are arranged in an array, the size of the device increases, which may make it difficult to use in small information terminals such as smartphones. Furthermore, when visible light sources are arranged in an array, data processing may become complicated. Furthermore, using multiple light sources to increase the information data processing capacity complicates the device configuration, resulting in extremely high costs. Therefore, it is not practical to apply such a configuration to a consumer transmission device.

[0077] When visible light is used in an optical communication system, the speed at which visible light signals are generated is high, and miniaturization and cost reduction are possible.

[0078] The laser diode 6030 for optical communication systems uses a red LD 41r, a green LD 41g, and a blue LD 41b, each of which emits visible light. The LDs are continuously on. "Continuously" means that the LDs are on while transmitting a visible light signal to a receiving device. The wavelength of the visible light 1 emitted by the LDs is generally in the range of 380 nm to 830 nm. The optical modulation element for optical communication systems uses optical elements 101, 102, and 103 that function as LN modulators. Therefore, a visible light signal can be generated by current modulation of the LD and voltage modulation of the LN based on an electrical signal received from the electrical signal generating element 6013. When generating the visible light signal 2, only one of the current modulation of the LD and voltage modulation of the LN may be used.

[0079] Optical elements 101, 102, and 103 are Mach-Zehnder optical modulators, and when a visible light signal is generated by only voltage modulation of LN, the time required to modulate visible light 1 to bright light or dark light using a Mach-Zehnder optical modulator is shorter than the time required to switch a visible light source on and off. Using optical elements with laser diodes in an optical communication system increases the speed at which visible light signals are generated.

[0080] In this way, by using the optical element according to the present disclosure in an optical communication system, it is possible to achieve miniaturization of the optical communication system.

[0081] "Smart Glasses Embodiment" Next, smart glasses using an optical engine including an optical element according to the present disclosure will be described. Smart glasses, such as AR (Augmented Reality) glasses and VR (Virtual Reality) glasses, are expected to be small wearable devices. In such devices, optical elements that emit full-color visible light are used as central elements for rendering high-quality images. FIG. 17 is a conceptual diagram illustrating an optical engine 5001 according to this embodiment. The illustration shows the optical engine 5001 mounted on a frame 10010 of glasses 10000. The symbol L denotes image display light.

[0082] The optical engine 5001 has a light source unit 1001 and a light scanning mirror 3001. As the light source unit 1001 provided in the optical engine 5001, the light source unit according to the above-described embodiment is used.

[0083] The light source unit 1001 may include a built-in optical element 201 with laser diodes including a red laser 41r, a green laser 41g, and a blue laser 41b. The laser light emitted from the light source unit 1001 attached to the eyeglass frame is reflected by an optical scanning mirror and enters the human eye, where an image (video) is projected directly onto the retina.

[0084] Furthermore, a module incorporating a near-infrared laser, a near-infrared LN optical waveguide or a near-infrared Si waveguide, and an optical element with a laser diode that further adds a near-infrared and visible light multiplexer can be used as the light source unit 1001. With this configuration, an image is projected directly onto the retina while performing eye tracking.

[0085] The optical scanning mirror 3001 is, for example, a MEMS mirror. In order to project a 2D image, it is preferable that the optical scanning mirror 3001 be a two-axis MEMS mirror that oscillates so as to reflect laser light while changing the angle in the horizontal direction (X direction) and the vertical direction (Y direction).

[0086] The optical engine 5001 has a collimator lens, a slit, and an ND filter as an optical system 2001 that optically processes the laser light emitted from the light source unit 1001. This optical system 2001 is an example, and other configurations may be used.

[0087] The optical engine 5001 includes a laser driver 1100, an optical scanning mirror driver 1200, and a video controller 1300 that controls these drivers.

[0088] In the optical engine 5001, three wavelengths are combined and output from the light source unit 1001, so each optical component can be made into a single component and made compact. Also, since white light is produced in a single beam spot, it is easier to increase the resolution.

[0089] In this way, by using an optical engine including an optical element according to the present disclosure in smart glasses, the overall size of the smart glasses can be reduced.

[0090] Computer Embodiments Next, as another application example, an embodiment of a computer using the optical element according to the present disclosure will be described. A computer 20000 shown in Fig. 18 includes an optical integrated circuit 20001 (hereinafter referred to as PIC) using the optical element according to the present disclosure, optical wiring 20002, a graphics processing unit 20003 (hereinafter referred to as GPU), and a central processing unit (CPU) 20004.

[0091] The PIC 20001 is connected to an optical wiring 20002. The PUC 20001 is provided at a connection point with the optical wiring of the GPU 20003a, 20003b, 20003c, 20003d, or the CPU 20004. The GPUs are connected to each other, or the GPUs are connected to the CPUs via optical wiring, and the PIC 20001 is provided at the connection point of each GPU.

[0092] In this way, an optical computer 20000 can be realized by using a PIC20001 including an optical element according to the present disclosure. Conventional optical elements are large, but this optical element, which has been miniaturized, can transmit optical signals, dramatically improving computer performance. Furthermore, because it is miniaturized on a single chip, it can be installed in computers that could not be realized with conventional optical elements. The computer according to the present disclosure is particularly suitable for computers used in fields such as AI, where high-speed exchange of information is required between GPUs and between CPUs and GPUs within a computer.

[0093] The optical element according to the present disclosure is an optical element comprising a sapphire substrate having a first optical waveguide and another substrate different from the sapphire substrate, wherein the first optical waveguide is made of a lithium niobate film provided on one surface of the sapphire substrate, and the first optical waveguide is sandwiched between the sapphire substrate and the other substrate different from the sapphire substrate.

[0094] In another aspect of the optical element according to the present disclosure, the sapphire substrate further has a first electrode, and the first optical waveguide and the first electrode form a Mach-Zehnder optical modulator.

[0095] An optical element according to another aspect of the present disclosure is characterized in that the substrate different from the sapphire substrate is a silicon substrate, the silicon substrate has a second optical waveguide, the second optical waveguide is made of a polysilicon film or a silicon nitride film provided on the silicon substrate, and the second optical waveguide is sandwiched between the sapphire substrate and the silicon substrate.

[0096] In an optical element according to another aspect of the present disclosure, the first optical waveguide and the second optical waveguide are optically connected to each other.

[0097] An optical element according to another aspect of the present disclosure further includes a laser diode, the laser diode being connected to either the first optical waveguide or the second optical waveguide.

[0098] The optical element according to the present disclosure further includes an electric circuit and a second electrode connected to the electric circuit and applying a voltage to the Mach-Zehnder optical modulator via the first electrode, and the electric circuit and the second electrode are sandwiched between the sapphire substrate and another substrate different from the sapphire substrate, and operates as an optical modulator.

[0099] The optical element according to the present disclosure is characterized in that visible light of 400 nm to 800 nm propagates through the first optical waveguide.

[0100] The optical element according to the present disclosure is characterized in that near-infrared light of 800 nm to 1600 nm propagates through the first optical waveguide.

[0101] The optical element according to the present disclosure is characterized in that the visible light has three wavelengths of red, green, and blue.

[0102] The optical communication system according to the present disclosure is characterized by using the optical element according to the present disclosure.

[0103] The smart glasses according to the present disclosure are characterized by using the optical element according to the present disclosure.

[0104] The computer according to the present disclosure comprises a PIC including an optical element according to the present disclosure, optical wiring, a plurality of GPUs, and a CPU, wherein the PIC is provided in the GPU and the CPU, and the PIC is connected to the plurality of GPUs or the GPU and the CPU via the optical wiring.

[0105] A manufacturing method of an optical element according to the present disclosure is a manufacturing method of an optical element including a substrate different from a sapphire substrate and the sapphire substrate, and includes: a first substrate patterning step of patterning the substrate different from the sapphire substrate to form a first pattern on the substrate different from the sapphire substrate; a second substrate patterning step of forming a first optical waveguide on one surface of the sapphire substrate to form a second pattern; a wafer bonding step of bonding one surface of the substrate different from the sapphire substrate on which the first pattern has been formed in the first substrate patterning step to the one surface of the sapphire substrate having the second pattern formed in the second substrate patterning step; and a dicing step of dicing the sapphire substrate and the substrate different from the sapphire substrate that have been integrated in the wafer bonding step.

[0106] Another aspect of the method for manufacturing an optical element according to the present disclosure is characterized in that the first substrate patterning step further comprises forming a first through hole in a substrate other than the sapphire substrate and filling the first through hole with metal.

[0107] In another aspect of the method for manufacturing an optical element according to the present disclosure, the second substrate patterning step further comprises forming a second through hole in the sapphire substrate and filling the second through hole with a metal.

[0108] Another aspect of the method for manufacturing an optical element according to the present disclosure is characterized in that the wafer bonding step is performed by surface activated bonding or atomic diffusion bonding.

[0109] Another aspect of the method for manufacturing an optical element according to the present disclosure is characterized in that the wafer bonding step uses a resin for bonding.

[0110] Although silicon substrates have been exemplified above as substrates other than sapphire substrates that constitute optical elements, other substrates such as GaAs substrates and InP substrates can also be used. [Explanation of symbols]

[0111] 11 Silicon substrate (substrate different from sapphire substrate) 12 Core Layer 12a Optical waveguide on the silicon substrate side (Si optical waveguide) 13 Cladding layer on the silicon substrate side (Si cladding layer) 14a Through electrode on the silicon substrate side (Si through electrode) 14b Signal electrode on silicon substrate side (Si signal electrode) 14c Ground electrode on the silicon substrate side (Si ground electrode) 15a CMOS circuits (electrical circuits) containing transistors 21 Sapphire substrate 22 Lithium niobate thin film (LN thin film) 23 LN side cladding layer (LN cladding layer) 24 Mach-Zehnder Optical Waveguide (MZI Optical Waveguide) 24a LN ridge section (optical input / output section)

Claims

1. a sapphire substrate having a first optical waveguide; an optical element comprising a substrate different from the sapphire substrate, the first optical waveguide is made of a lithium niobate film provided on one surface of a sapphire substrate, The optical element is characterized in that the first optical waveguide is disposed between the sapphire substrate and a substrate different from the sapphire substrate.

2. the sapphire substrate further has a first electrode; 2. The optical element according to claim 1, wherein the first optical waveguide and the first electrode constitute a Mach-Zehnder type optical modulator.

3. the substrate different from the sapphire substrate is a silicon substrate; the silicon substrate has a second optical waveguide; the second optical waveguide is made of a polysilicon film or a silicon nitride film provided on the silicon substrate, 2. The optical element according to claim 1, wherein the second optical waveguide is sandwiched between the sapphire substrate and the silicon substrate.

4. The optical element according to claim 3 , wherein the first optical waveguide and the second optical waveguide are optically connected.

5. a laser diode; 5. The optical element according to claim 1, wherein the laser diode is connected to either the first optical waveguide or the second optical waveguide.

6. An electric circuit, a second electrode connected to the electric circuit and applying a voltage to the Mach-Zehnder optical modulator via the first electrode; the electric circuit and the second electrode are sandwiched between the sapphire substrate and a substrate different from the sapphire substrate; 3. The optical element according to claim 2, which operates as an optical modulator.

7. 6. The optical element according to claim 5, wherein visible light of 400 nm to 800 nm propagates through said first optical waveguide.

8. 6. The optical element according to claim 5, wherein near-infrared light of 800 nm to 1600 nm propagates through the first optical waveguide.

9. 8. The optical element according to claim 7, wherein the visible light has three wavelengths of red, green, and blue.

10. An optical communication system using the optical element according to claim 8.

11. Smart glasses using the optical element according to claim 9.

12. A PIC including the optical element according to claim 6; Optical wiring and Multiple GPUs; a CPU; The PIC is provided in the GPU and the CPU, and the PIC is connected to the plurality of GPUs or the GPU and the CPU via the optical fiber line.

13. A method for manufacturing an optical element including a substrate different from a sapphire substrate and the sapphire substrate, a first substrate patterning step of patterning a substrate different from the sapphire substrate to form a first pattern on the substrate different from the sapphire substrate; forming a first optical waveguide on one surface of the sapphire substrate; a second substrate patterning step of forming a second pattern on one surface of the substrate; a wafer bonding step of bonding one surface of a substrate different from the sapphire substrate on which the first pattern is formed in the first substrate patterning step to the one surface of the sapphire substrate on which the second pattern is formed in the second substrate patterning step; a dicing step of dicing the sapphire substrate and a substrate different from the sapphire substrate that has been integrated in the wafer bonding step.

14. The first substrate patterning step further includes:

14. The method for manufacturing an optical element according to claim 13, further comprising forming a first through hole in a substrate other than the sapphire substrate, and filling the first through hole with a metal.

15. The second substrate patterning step further includes:

14. The method for manufacturing an optical element according to claim 13, further comprising forming a second through hole in the sapphire substrate and filling the second through hole with a metal.

16. 14. The method for manufacturing an optical element according to claim 13, wherein the wafer bonding step is performed by a surface activated bonding method or an atomic diffusion bonding method.

17. 14. The method for manufacturing an optical element according to claim 13, wherein the wafer bonding step uses a resin for bonding.

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