Optical chip, optical module, optical communication device, and manufacturing method

Abstract

The present application provides an optical chip, an optical module, an optical communication device, and a manufacturing method. The optical chip comprises a lithium niobate layer, a buried oxide layer, and a substrate from top to bottom, wherein an electro-optic modulator is provided in the lithium niobate layer; an integrated waveguide structure is provided in the buried oxide layer, and the electro-optic modulator is used for modulating signal light transmitted in the integrated waveguide structure; the substrate is bonded to the buried oxide layer, and the substrate satisfies at least one or more of the following conditions: the dielectric constant is less than or equal to 10, or the resistivity is greater than or equal to 10 KΩ / cm. That is, the substrate of the optical chip can be flexibly selected by means of bonding technology, so that impedance matching can be performed on a lithium niobate film and a new substrate, thereby reducing radio frequency signal loss and improving the modulation bandwidth of the electro-optic modulator.

Description

An optical chip, an optical module, an optical communication device, and a method for fabricating them.

[0001] This application claims priority to Chinese Patent Application No. 202411794693.6, filed on December 6, 2024, with the invention entitled "An optical chip, optical module, optical communication device and preparation method", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optical communication technology, and in particular to an optical chip, an optical module, an optical communication device, and a method for its fabrication. Background Technology

[0003] An electro-optic modulator is a modulator that utilizes the electro-optic effect of electro-optic crystals, such as lithium niobate crystals (LiNbO3). Electro-optic modulators modulate the phase, amplitude, intensity, and polarization state of signal light by applying voltage to the electro-optic crystal, thereby changing its refractive index.

[0004] Lithium niobate crystals possess numerous superior optical properties, and in recent years, emerging lithium niobate thin-film technology has garnered significant attention in integrated photonics research. Compared to traditional bulk lithium niobate modulators, thin-film lithium niobate modulators enhance optical confinement through waveguide etching, greatly reducing device size. Furthermore, lithium niobate substrates enable large-scale wafer fabrication, making them ideal materials for electro-optic modulators.

[0005] However, in lithium niobate-based electro-optic modulators, impedance matching between the lithium niobate film and the semiconductor substrate is difficult, leading to increased RF signal loss and affecting modulation bandwidth. One impedance matching method is to hollow out the semiconductor substrate; however, this method impacts the overall reliability and robustness of the chip, as well as subsequent cutting, film application / removal, and packaging processes. Therefore, achieving impedance matching between the lithium niobate film and the semiconductor substrate in lithium niobate electro-optic modulators while ensuring chip reliability and process compatibility is a pressing technical problem that needs to be solved. Summary of the Invention

[0006] This application provides an optical chip, an optical module, an optical communication device, and a fabrication method. The method involves replacing the substrate of an electro-optic modulator based on a lithium niobate thin film using a bonding process to match the impedance of the lithium niobate thin film with that of the semiconductor substrate.

[0007] In a first aspect, an optical chip is provided, comprising, from top to bottom, a lithium niobate layer, a buried oxide layer, and a substrate, wherein: an electro-optic modulator is disposed in the lithium niobate layer; an integrated waveguide structure is disposed in the buried oxide layer, and the electro-optic modulator is used to modulate the signal light transmitted in the integrated waveguide structure; the substrate is bonded to the buried oxide layer, and the substrate satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10; or electrical resistance greater than or equal to 10 kΩ / cm. That is, the bonding technology enables flexible selection of the substrate for the optical chip, thereby achieving impedance matching between the lithium niobate film and the new substrate, reducing radio frequency signal loss, and improving the modulation bandwidth of the electro-optic modulator.

[0008] In conjunction with the first aspect, in certain implementations of the first aspect, wherein: the substrate material is quartz; or the substrate material is sapphire; or the substrate material is silicon, the resistivity of which is greater than 10 kΩ / cm; or the substrate includes a trap-rich layer. Wherein, the dielectric constant of the quartz substrate is less than 5. The resistivity of the sapphire substrate is greater than 1000 Ω / cm. The resistivity of the high-resistivity silicon (HR Si) is greater than 10 kΩ / cm. The trap-rich silicon can capture free parasitic charges in the buried oxide layer, further improving the performance of the optical chip.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the bonding between the substrate and the buried oxide layer includes: direct bonding between the substrate and the buried oxide layer; or an adhesive layer is disposed between the substrate and the buried oxide layer.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the lithium niobate layer is bonded to the buried oxide layer. Specifically, this bonding can refer to direct bonding, that is, connecting the two surfaces together through physical contact, or it can be understood as the two surfaces being bonded by van der Waals forces. In the case of direct bonding, the double cantilever beam (DCB) method can be used for measurement. Alternatively, bonding can also specifically refer to bonding using an adhesive, such as a polymer adhesive, epoxy resin, polyurethane, etc. In this case, the two bonded surfaces are also provided with an adhesive layer.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, wherein: the buried oxide layer further includes a first layer and / or a second layer; the first layer is composed of silicon dioxide, and the bonding between the substrate and the buried oxide layer includes: bonding between the substrate and the first layer; the second layer is composed of silicon dioxide, and the lithium niobate layer is bonded to the second layer.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the optical chip is provided with a first coupler and a second coupler, wherein: the first coupler is used to receive a first signal light from the integrated waveguide and send the first signal light to the electro-optic modulator; the electro-optic modulator is used to modulate the first signal light to obtain a second signal light; and the second coupler is used to receive the second signal light from the electro-optic modulator and send the second signal light to the integrated waveguide.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the buried oxide layer includes a third layer and a fourth layer, wherein: the third layer is adjacent to the substrate and includes a first waveguide and / or a second waveguide, wherein the first waveguide is used to receive the third signal light input to the optical chip, and the second waveguide is used to output the fourth signal light from the optical chip; the first and second waveguides are composed of silicon material; the fourth layer is adjacent to the lithium niobate layer and includes a polarization beamsplitter and / or a polarization beam combiner made of silicon nitride material. That is, the transmission of the signal light is mainly carried out by silicon-based waveguides, and silicon material has a higher refractive index than silicon nitride material, which can effectively constrain the signal light. The passive structure prepared by silicon nitride has the characteristics of low transmission loss and low transmission loss with temperature variation, and can be used to realize polarization beam splitting and beam combining of signal light. Using the above composite method, the loss of the optical chip can be minimized.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the optical chip further includes a third coupler and / or a fourth coupler, wherein: the third coupler is used to receive a fifth signal light from the third layer and transmit the fifth signal light to the fourth layer; the fourth coupler is used to receive a sixth signal light from the fourth layer and transmit the sixth signal light to the third layer. Through the third coupler and / or the fourth coupler, the transmission of signal light between the third and fourth layers can be realized, thereby forming a complete optical path.

[0015] In a second aspect, an optical module is provided, comprising: a light source, a signal generation chip, and an optical chip of the first aspect and any possible implementation thereof; and / or a signal processing chip of the optical chip of the first aspect and any possible implementation thereof.

[0016] Thirdly, an optical communication system is provided, including an optoelectronic device and an optical module as described in the second aspect, wherein the optoelectronic device is connected to the optical module, and the optoelectronic device is any one of an optical switch, an optical fiber router, or an optical fiber network card.

[0017] Fourthly, an optical communication system is provided, including an optoelectronic device and an optical module as described in the second aspect, wherein the optoelectronic device is connected to the optical module, and the optoelectronic device is any one of an optical switch, an optical fiber router, or an optical fiber network card.

[0018] Fifthly, a method for fabricating an optical chip is provided, comprising: fabricating a buried oxide layer on a silicon substrate, wherein an integrated waveguide structure is disposed in the buried oxide layer; bonding the buried oxide layer and a lithium niobate layer, wherein an electro-optic modulator is disposed in the lithium niobate layer, the electro-optic modulator being used to modulate the signal light transmitted in the integrated waveguide structure; removing the silicon substrate; and bonding the buried oxide layer and a first substrate, wherein the first substrate satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10, and resistance greater than or equal to 100 Ω / cm. By bonding the lithium niobate layer and the buried oxide layer, all the design advantages of modulators fabricated on single-crystal thin-film lithium niobate substrates, such as small size, high bandwidth, and low driving voltage, can be inherited. Furthermore, this technology is compatible with complementary metal oxide semiconductor (CMOS) processes, inherits the excellent passive properties of SOI and SiN, further improves chip light extraction and extinction ratio performance, and can also achieve integrated design, greatly reducing chip size and supporting the evolution of miniaturized module packaging. In addition, by flexibly selecting new substrate types and integration steps, it is possible to ensure chip performance without large-area hollowing and to guarantee the mechanical robustness of the chip.

[0019] In conjunction with the fifth aspect, in some implementations of the fifth aspect, before removing the silicon substrate, the method further includes: bonding a lithium niobate layer and a second substrate; after removing the silicon substrate, the method further includes: removing the second substrate. This second substrate can also be referred to as a handle wafer, used to ensure the overall stability of the optical chip after removing the silicon substrate.

[0020] In conjunction with the fifth aspect, in some implementations of the fifth aspect, after removing the silicon substrate, the method further includes: removing a first portion of the lithium niobate layer, wherein the first portion is the portion far from the buried oxide layer. This ensures the overall stability of the optical chip after removing the silicon substrate. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of an optical chip provided in an embodiment of this application.

[0022] Figure 2 is a schematic diagram of an electro-optic modulator provided in an embodiment of this application.

[0023] Figure 3 is a schematic diagram of a method for fabricating an optical chip according to an embodiment of this application.

[0024] Figure 4 is a schematic diagram of a method for bonding a buried oxide layer and a substrate according to an embodiment of this application.

[0025] Figure 5 is a schematic diagram of another method for bonding a buried oxide layer and a substrate provided in an embodiment of this application.

[0026] Figure 6 is a schematic diagram of an optical module provided in an embodiment of this application.

[0027] Figure 7 illustrates an optical communication system provided in an embodiment of this application. Detailed Implementation

[0028] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0029] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0030] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0031] In the description of the embodiments of this application, the terms "upper," "lower," "vertical," "horizontal," etc., indicate the orientation or positional relationship relative to the orientation or position of the components shown in the drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and not to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They can change accordingly depending on the orientation of the components in the drawings, and therefore should not be construed as limiting this application.

[0032] The terms “comprising” and “having” and any variations thereof used in the embodiments of this application shown below are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0033] In the embodiments of this application, the words "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Embodiments or designs described as "exemplary" or "for example" should not be construed as being more preferred or advantageous than other embodiments or designs. The use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner to facilitate understanding.

[0034] An electro-optic modulator is a modulator that utilizes the electro-optic effect of electro-optic crystals, such as lithium niobate crystals (LiNbO3). Electro-optic modulators modulate the phase, amplitude, intensity, and polarization state of signal light by applying voltage to the electro-optic crystal, thereby changing its refractive index.

[0035] Lithium niobate crystals possess numerous superior optical properties, including a large linear electro-optic coefficient (33 pm / V), a wide transparency band of 550–5500 nm, stable chemical properties, and thermal stability. These make them suitable for fabricating optical waveguides and high-performance electro-optic modulators, and they have long been considered one of the most promising matrix materials for integrated photonics. In recent years, emerging lithium niobate thin-film technology has received considerable attention in integrated photonics research. Compared to traditional bulk lithium niobate modulators, thin-film lithium niobate modulators significantly reduce device size by etching waveguides to enhance optical confinement. Furthermore, lithium niobate substrates allow for large-scale wafer fabrication, making them ideal electro-optic modulator materials. Thin-film lithium niobate modulators are suitable for coherent applications at baud rates of 140 GHz and higher, and can be coupled with uncooled, miniaturized packaging.

[0036] However, in lithium niobate-based electro-optic modulators, impedance matching between the lithium niobate film and the semiconductor substrate is difficult, leading to increased RF signal loss and affecting modulation bandwidth. One impedance matching method is to hollow out the semiconductor substrate; however, this method impacts the overall reliability and robustness of the chip, as well as subsequent cutting, film application / removal, and packaging processes. Therefore, achieving impedance matching between the lithium niobate film and the semiconductor substrate in lithium niobate electro-optic modulators while ensuring chip reliability and process compatibility is a pressing technical problem that needs to be solved.

[0037] In view of this, embodiments of this application provide an optical chip, an optical module, an optical communication device, and a fabrication method, which replaces the substrate of an electro-optic modulator based on a lithium niobate thin film through a bonding process to match the impedance of the lithium niobate thin film and the semiconductor substrate.

[0038] Figure 1 is a schematic diagram of the structure of an optical chip provided in an embodiment of this application. As shown in Figure 1, the optical chip includes, from top to bottom, a lithium niobate layer 110, a buried oxide (BOX) layer, and a substrate 130.

[0039] An electro-optic modulator is disposed in the lithium niobate layer 110. The structure of the electro-optic modulator is described in conjunction with Figure 2 below.

[0040] An integrated waveguide structure is provided in the buried oxide layer 120, and an electro-optic modulator is used to modulate the signal light transmitted in the integrated waveguide structure.

[0041] The buried oxide layer 120 can also be called the buried oxide layer, which includes insulating materials such as silicon dioxide (SiO2).

[0042] The integrated waveguide structure may include one or more passive optical waveguide devices, such as waveguides, couplers, splitters, beam splitters, waveguide Bragg gratings, arrayed waveguide gratings, Mach-Zehnder interferometers, ring resonators, etc., depending on the specific requirements. The integrated waveguide structure may be made of one or more materials; for example, it may include silicon waveguide structures, silicon nitride (SiN) waveguide structures, etc.

[0043] In some implementations, the optical chip includes a first coupler and a second coupler, wherein: the first coupler is used to receive a first signal light from the integrated waveguide and send the first signal light to the electro-optic modulator; the electro-optic modulator is used to modulate the first signal light to obtain a second signal light; and the second coupler is used to receive the second signal light from the electro-optic modulator and send the second signal light to the integrated waveguide.

[0044] The first coupler and the second coupler can be specifically designed as vertical thermally adiabatic couplers, grating couplers, or other structures. Through the first coupler and / or the second coupler, the signal light can be modulated in the lithium niobate layer 110 and transmitted in the integrated waveguide structure included in the buried oxide layer 120, thus forming a complete optical path.

[0045] Figure 1 shows a specific structure of an integrated waveguide structure in a buried oxide layer 120.

[0046] In some implementations, the buried oxide layer 120 includes a first layer 121 and / or a second layer 124. The first layer 121 is composed of silicon dioxide and is bonded to the lithium niobate layer 110. The second layer 124 is composed of silicon dioxide and is bonded to the substrate 130.

[0047] In some implementations, the buried oxygen layer 120 includes a third layer 123 and a fourth layer 122.

[0048] The third layer 123 is adjacent to the substrate 130 and includes a first waveguide and / or a second waveguide. The first waveguide receives a third signal light input to the optical chip, and the second waveguide outputs a fourth signal light from the optical chip. Both the first and second waveguides are made of silicon. The fourth layer 122 is adjacent to the lithium niobate layer 110 and includes a silicon nitride polarization beamsplitter and / or polarization combiner. Furthermore, the fourth layer 122 may also include at least one of the following silicon nitride structures: an end-face coupler, a grating, or a waveguide. The thickness of the third layer 123 can be greater than or equal to 100 nm and less than or equal to 300 nm. The thickness of the fourth layer 122 can be greater than or equal to 100 nm and less than or equal to 600 nm. The specific arrangement of the optical waveguide structures in the third layer 123 and the fourth layer 122 within and between layers is determined according to actual conditions. That is, this application does not impose any limitation on the distance between the optical waveguide structure included in the third layer 123 and the optical waveguide structure included in the fourth layer 122 in the vertical direction (i.e., perpendicular to the substrate 130 direction). Furthermore, it does not impose any limitation on the horizontal (i.e., parallel to the substrate 130 direction) arrangement of the optical waveguide structures included in the third layer 123 and the fourth layer 122. In addition, the optical waveguide structures in the third layer 123 and the fourth layer 122 may include vertically overlapping transition structures, as determined according to the actual situation.

[0049] In other words, the signal light transmission is mainly handled by silicon-based waveguides. Silicon has a higher refractive index than silicon nitride, which effectively confines the signal light. Meanwhile, passive structures made of silicon nitride exhibit low transmission loss and low temperature-dependent transmission loss, making them suitable for polarization beam splitting and combining of signal light. Utilizing this composite approach, the losses of the optical chip can be minimized.

[0050] In some implementations, the optical chip further includes a third coupler and / or a fourth coupler, wherein: the third coupler is used to receive the fifth signal light from the third layer 123 and transmit the fifth signal light to the fourth layer 122; the fourth coupler is used to receive the sixth signal light from the fourth layer 122 and transmit the sixth signal light to the third layer 123. The third and fourth couplers can specifically be structures such as vertical thermally adiabatic couplers or grating couplers. Through the third and / or fourth couplers, signal light transmission between the third layer 123 and the fourth layer 122 can be achieved, thereby forming a complete optical path.

[0051] In some implementations, a photodetector (PD) can also be provided in the optical chip to detect the signal light transmitted in the optical chip. This photodetector can be a silicon (Si) photodetector, a germanium (Ge) photodetector, a waveguide-coupled Ge / Si photodetector, etc. Figure 1 exemplarily illustrates the structure of a photodetector. As shown in Figure 1, the photodetector can be a PN junction type photodetector. The photodetector can include a P-type doped region 141, an N-type doped region 142, and an intrinsic region 140. The P-type doped region 141 can include silicon material implanted with P-type ions, which can specifically be trivalent elements (such as boron, aluminum, etc.). The N-type doped region 142 can include silicon material implanted with N-type ions, which can specifically be pentavalent elements (such as phosphorus, arsenic, etc.). The P-type doped region 141 is connected to a first electrode 143, and the N-type doped region is connected to a second electrode 144. The first electrode 143 and the second electrode 144 can be metal electrodes. The intrinsic region 140 is located between the P-type doped region 141 and the N-type doped region 142. The intrinsic region 140 is disposed within a recess 145 formed of undoped silicon material. Undoped germanium material can be deposited in the intrinsic region 140 to improve the responsivity and bandwidth of the photodetector. Furthermore, a photodetector can also be disposed in the lithium niobate layer 110, or the photodetector can penetrate through the lithium niobate layer 110 and the buried oxide layer 120, depending on the specific circumstances.

[0052] The substrate 130 is bonded to the buried oxide layer 120, wherein the substrate 130 satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10; resistivity greater than or equal to 10 kΩ / cm. That is, the bonding technology enables flexible selection of the substrate 130 for the optical chip, thereby achieving impedance matching between the lithium niobate film and the new substrate 130, reducing RF signal loss, and improving the modulation bandwidth of the electro-optic modulator. The thickness of the substrate 130 is greater than or equal to 100 μm and less than or equal to 1000 μm, thus supporting the buried oxide layer 120 and the lithium niobate layer 110.

[0053] In some implementations, the substrate 130 can specifically be one of quartz, sapphire, high-resistivity silicon, or trap-rich silicon substrate 130. The quartz substrate 130 has a dielectric constant of less than 5. Sapphire has a resistivity greater than 1000 Ω / cm. High-resistivity silicon (HR Si) has a resistivity greater than 10 KΩ / cm. Trap-rich silicon can capture free parasitic charges in the buried oxide layer 120, further improving the performance of the optical chip.

[0054] Specifically, the aforementioned bonding can refer to direct bonding, that is, connecting two surfaces together through physical contact, or it can be understood as the two surfaces being bonded by van der Waals forces. In the case of direct bonding, the double cantilever beam (DCB) method can be used for measurement. Alternatively, bonding can also specifically refer to bonding using an adhesive, such as a polymer adhesive, epoxy resin, polyurethane, etc. In this case, an adhesive layer is also provided on the two bonded surfaces. The aforementioned bonding can specifically refer to lithium niobate layer 110 and buried oxide layer 120, buried oxide layer 120 and substrate 130, lithium niobate layer 110 and first layer 121, second layer 124 and substrate 130, as determined by the specific description.

[0055] Figure 2 is a schematic diagram of an electro-optic modulator provided in an embodiment of this application. As shown in Figure 2(a), (b), and (c), four electro-optic modulators on X-cut lithium niobate films are shown respectively, with the signal light propagating along the y-axis.

[0056] As shown in Figure 2(a), the electro-optic modulator of this application can be a phase modulator. The phase modulator includes a first electrode 211, a second electrode, and a waveguide located between the first electrode 211 and the second electrode. The first electrode 211 is connected to the positive terminal of a power supply, and the second electrode is grounded. The first electrode 211 and the second electrode are used to apply power to the waveguide to perform phase modulation on the signal light propagating along the waveguide.

[0057] As shown in Figure 2(b), the electro-optic modulator of this application can be a Mach-Zehnder interferometer (MZI) modulator. The MZI modulator includes a first port 224, a first modulation arm 226, a second modulation arm 227, and a second port 225. One end of the first modulation arm 226 is connected to the first port 224, and the other end of the first modulation arm 226 is connected to the second port 225. One end of the second modulation arm 227 is connected to the first port 224, and the other end of the second modulation arm 227 is connected to the second port 225. Figure 2(b) shows one electrode distribution.

[0058] In one implementation, the MZI modulator may include a third electrode 221, a fourth electrode 222, and a fifth electrode 223. The fourth electrode 222 is disposed between the first modulation arm 226 and the second modulation arm 227. The third electrode 221 is disposed on one side of the first modulation arm 226. The fifth electrode 223 is disposed on one side of the second modulation arm 227. The third electrode 221 and the fifth electrode 223 are grounded, and the fourth electrode 222 is connected to the positive terminal of the power supply. The first port 224 is used to receive a first signal light. After passing through the first port 224, the first signal light is split into a second signal light and a third signal light. The second signal light is transmitted along the first modulation arm 226, and the third signal light is transmitted along the second modulation arm 227. The third electrode 221 and the fourth electrode 222 are used to perform phase modulation on the second signal light. The fourth electrode 222 and the fifth electrode 223 are used to perform phase modulation on the third signal light. The second port 225 is used to receive the modulated second signal light and the modulated third signal light, and to combine the modulated second signal light and the modulated third signal light to obtain the fourth signal light. The intensity of the fourth signal light is maximum when the phase difference between the modulated second signal light and the modulated third signal light is 0. The intensity of the fourth signal light is minimum when the phase difference between the modulated second signal light and the modulated third signal light is π.

[0059] In addition, MZI modulators may include more or fewer electrodes, depending on the specific circumstances.

[0060] As shown in Figure 2(c), the electro-optic modulator of this application can be an orthogonal modulator, which may include a polarization beamsplitter 231, a first MZI modulator 232, a second MZI modulator 233, and a polarization beam combiner 234. The polarization beamsplitter 231 includes a third port, a first branch waveguide, and a second branch waveguide. The third port is used to receive a fifth signal light. The fifth signal light is split at the third port into a sixth signal light with a first polarization mode and a seventh signal light with a second polarization mode. The sixth signal light enters the first MZI modulator 232, and the seventh signal light enters the second MZI modulator 233. The first MZI modulator 232 modulates the sixth signal light, and the second MZI modulator modulates the seventh signal light. The polarization beam combiner 234 combines the modulated sixth and seventh signal lights to obtain an eighth signal light. The eighth signal light includes signal lights with two polarization modes, each modulated with information. The first polarization mode and the second polarization mode can be orthogonal, and the first polarization mode and the second polarization mode can be a transverse magnetic (TM) mode and a transverse electric (TE) mode, respectively. Furthermore, the polarization beam splitter 231 and / or the polarization beam combiner 234 can also be disposed in the buried oxide layer of the optical chip, depending on the actual situation.

[0061] In addition, electro-optic modulators can also take the form of Michelson interferometer modulators (MIM), etc., which will not be elaborated here.

[0062] Figure 3 is a schematic diagram of a method for fabricating an optical chip according to an embodiment of this application. As shown in Figure 3, the method includes steps S310-S340.

[0063] It should be understood that the following steps are based on the structure shown in Figure 1. When preparing optical chips with other structures provided in this application, the steps shown in Figure 2 can be modified and replaced according to the specific structure.

[0064] S310 involves fabricating a buried oxide layer on a silicon substrate, within which an integrated waveguide structure is disposed.

[0065] The buried oxide layer can be formed using silicon-on-insulator (SOI) technology, which involves depositing an insulating layer on a silicon substrate. The fabrication method for the buried oxide layer can be adapted to foundry process baselines, supporting the commercialization and application of optical chips.

[0066] Taking a buried oxide layer comprising the first, second, third, and fourth layers as shown in Figure 1 as an example, the first and second layers can be obtained using processes such as plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), and thermal oxidation. The waveguide structure included in the third layer can be obtained using PECVD or LPCVD processes. The waveguide structure included in the fourth layer can be obtained using high-density plasma (HDP) CVD, PECVD, or CVD using tetraethoxysilane (TEOS) as a silicon source. Furthermore, the buried oxide layer can be further mechanically and / or chemically polished.

[0067] In addition, the buried oxygen layer can also be obtained through smart cut technology, and this application does not limit this.

[0068] S320 consists of a bonded buried oxide layer and a lithium niobate layer. An electro-optic modulator is incorporated within the lithium niobate layer to modulate the signal light transmitted within the integrated waveguide structure.

[0069] The bonding of the buried oxide layer and the lithium niobate layer uses smart cut technology, and the specific process flow is illustrated in Figure 6.

[0070] S330, remove silicon substrate.

[0071] In some implementations, before removing the silicon substrate, the method further includes bonding a lithium niobate layer and a second substrate. This second substrate, also known as a handle wafer, is used to ensure the overall stability of the optical chip after the silicon substrate is removed.

[0072] In some implementations, the bonded lithium niobate layer is bulk, meaning that the lithium niobate layer has a thickness greater than or equal to 200 μm and less than or equal to 1000 μm during bonding. This ensures the overall stability of the optical chip after the silicon substrate is removed.

[0073] S340, bonding a buried oxide layer and a first substrate, wherein the substrate satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10, and resistance greater than or equal to 100 Ω / cm.

[0074] In the case where the lithium niobate layer is bonded to the second substrate, after bonding the buried oxide layer and the first substrate, the method further includes removing the second substrate. This completes the overall fabrication of the optical chip.

[0075] When the lithium niobate layer is bulk, after bonding the buried oxide layer and the first substrate, the method further includes removing a first portion of the lithium niobate layer, which is the portion far from the buried oxide layer. This completes the overall fabrication of the optical chip.

[0076] In the method shown in Figure 3, by bonding the lithium niobate layer and the buried oxide layer, all the design advantages of modulators fabricated on single-crystal thin-film lithium niobate substrates, such as small size, high bandwidth, and low drive voltage, can be inherited. Furthermore, this technology is compatible with complementary metal oxide semiconductor (CMOS) processes, inheriting the excellent passive properties of SOI and SiN, further improving chip performance such as light extraction and extinction ratio. It also enables integrated design, significantly reducing chip size and supporting the evolution of miniaturized module packaging. In addition, by flexibly selecting new substrate types and integration steps, chip performance can be ensured without large-area hollowing out, guaranteeing the chip's mechanical robustness.

[0077] The bonding technology provided in the embodiments of this application will now be described with reference to Figures 4, 5 and 6.

[0078] Figure 4 is a schematic diagram of a method for bonding a buried oxide layer and a substrate according to an embodiment of this application. As shown in Figure 4, the method includes steps (a)-(f).

[0079] (a) A buried oxide layer 420 is fabricated on a silicon substrate 410, wherein an integrated waveguide structure is disposed in the buried oxide layer 420.

[0080] (b) Bonding of buried oxide layer 420 and lithium niobate layer 430.

[0081] (c) Temporarily bond the lithium niobate layer 430 and the second substrate 440.

[0082] The second substrate 440, also known as a handle wafer, can be made of materials such as Si, SiC, or glass. The thickness of the second substrate 440 is greater than or equal to 200 μm and less than or equal to 1000 μm.

[0083] Temporary bonding can specifically refer to a thermo-press bonding process, which involves bonding the lithium niobate layer 430 and the second substrate 440 under high temperature and pressure. Alternatively, temporary bonding can specifically refer to an ultraviolet temporary bonding process, which involves bonding the lithium niobate layer 430 and the second substrate 440 with ultraviolet wafer temporary bonding adhesive and then curing the ultraviolet wafer temporary bonding adhesive with ultraviolet light.

[0084] (d) Removing the silicon substrate 410. Here, "removing the silicon substrate 410" can also be understood as "removing the silicon substrate 410". The process may specifically include grinding, wet etching, dry etching, etc., depending on the actual situation.

[0085] (e) Bonding the buried oxide layer 420 and the first substrate 450.

[0086] The bonding technique can be either temporary bonding or permanent bonding. Temporary bonding is similar to that described in step (a) above and will not be repeated here. Permanent bonding can specifically refer to direct bonding or adhesive bonding, both of which have been explained with reference to Figure 1 and will not be repeated here.

[0087] (f) Remove the second substrate 440.

[0088] The method for removing the second substrate 440 is determined based on the temporary bonding process between the lithium niobate layer 430 and the second substrate 440. For example, the second substrate 440 can be removed using bonding processes such as thermal slip, mechanical peeling, or laser bonding.

[0089] Figure 5 is a schematic diagram of another method for bonding a buried oxide layer and a substrate according to an embodiment of this application. As shown in Figure 5, the method includes steps (a)-(e).

[0090] (a) A buried oxide layer 520 is fabricated on a silicon substrate 510, wherein an integrated waveguide structure is disposed in the buried oxide layer 520.

[0091] (b) Bonding the buried oxide layer 520 and the lithium niobate layer 530. The bonded lithium niobate layer 530 is bulk, that is, the lithium niobate layer 530 satisfies a thickness greater than or equal to 200 μm and less than or equal to 1000 μm when bonded.

[0092] The lithium niobate layer 530 comprises a first portion 531 and a second portion 532. The first portion 531 is the portion of the original buried oxide layer 520. The second portion 532 is implanted with ions using ion implantation (IMP) technology; the thickness of the second portion 532 can be greater than or equal to 500 nm and less than or equal to 800 nm. After the buried oxide layer 520 and the lithium niobate layer 530 are bonded, the first portion 531, being the portion of the lithium niobate layer 530 furthest from the buried oxide layer 520, needs to be removed in subsequent processes.

[0093] (c) Remove silicon substrate 510. Here, "remove silicon substrate 510" can also be understood as "remove silicon substrate 510". The process may specifically include grinding, wet etching, dry etching, etc., depending on the actual situation.

[0094] (d) Bonding the buried oxide layer 520 and the first substrate.

[0095] The bonding technique can be either temporary bonding or permanent bonding. Temporary bonding is similar to that described in step (a) above and will not be repeated here. Permanent bonding can specifically refer to direct bonding or adhesive bonding, both of which have been explained with reference to Figure 1 and will not be repeated here.

[0096] (e) Removing the first portion 531 of the lithium niobate layer 530. This can be achieved by heat treatment to remove the first portion 531 of the lithium niobate layer 530, followed by chemical mechanical polishing (CMP) of the lithium niobate surface.

[0097] It should be understood that the specific sequence of steps described in Figures 3 to 5 above is merely illustrative, and the actual sequence is determined according to the process. It should also be understood that the specific semiconductor fabrication processes given above are merely illustrative, and the actual fabrication process can refer to the examples above or be selected according to the actual situation.

[0098] In addition, embodiments of this application also provide an optical module and an optical communication system, including an optical chip as described in FIG1, or an optical chip prepared using the preparation methods described in FIG3 to 6.

[0099] Figure 6 is a schematic diagram of an optical module provided in an embodiment of this application.

[0100] In some implementations, as shown in Figure 6(a), the optical module includes a light source 610, an optical chip 620, and a signal generation chip 630. The specific structure of the optical chip 620 is similar to that in Figure 1, and will not be described again here. In this case, the optical module can specifically refer to an optical transmission module.

[0101] The light source 610 is used to input a light beam into the electro-optic modulator 621 in the optical chip. The signal generation chip 630 is used to input an electrical signal into the electro-optic modulator 621, which modulates the light beam input to the electro-optic modulator 621 to generate signal light carrying information. The signal generation chip may specifically integrate a digital signal processing (DSP) module, a digital-to-analog conversion (DAC) module, etc., depending on the actual situation.

[0102] In some implementations, the light beam input from the light source can be specifically coherent light. The electro-optic modulator 621 can be an orthogonal modulator, and an electrical signal is used to modulate the light beam input to the electro-optic modulator 621 to generate signal light with two different polarization modes carrying information.

[0103] In some implementations, as shown in Figure 6(b), the optical module includes a light source 610, an optical chip 620, and a signal generation chip 630. The light source 610, optical chip 620, and signal generation chip 630 shown in Figure 6(b) are similar to those in Figure 6(a), and will not be described again here. In the case shown in Figure 6(b), the light source 610 is integrated into the optical chip 620, and the light source 610 can be in the form of a laser chip.

[0104] In some implementations, as shown in Figure 6(c), the optical module includes an optical chip 640 and a signal processing chip 650. In this case, the optical module can specifically refer to an optical receiving module. In some implementations, as shown in the figure, the optical chip 640 includes a polarization beamsplitter 641. The polarization beamsplitter 641 is used to receive mixed light and output signal light carrying two different polarization modes. A coherent receiver 642 is used to convert the two different polarization modes of signal light into two different electrical signals respectively. The signal processing chip 650 is used to process these two different electrical signals to obtain the information in the two different electrical signals. The signal processing chip 650 may specifically integrate an analog-to-digital conversion (ADC) module, a digital signal processing (DSP) module, etc., depending on the actual situation.

[0105] Furthermore, the optical module shown in Figure 6(c) can be combined with optical modules such as those in Figure 6(a) or Figure 6(b) to obtain an optical transceiver module.

[0106] Figure 7 illustrates an optical communication system provided in an embodiment of this application. As shown in Figure 7, the optical system may include optoelectronic devices and an optical module as shown in Figure 6. The optoelectronic device 710 can be any one of an optical switch, a fiber optic router, or a fiber optic network interface card (NIC), and is connected to the optical module 720.

[0107] Optoelectronic devices can include multiple ports, each corresponding to an optical transmission channel. These ports are connected to optical modules, enabling multi-channel, high-speed optical signal transmission. Optical switches can be used to exchange data between multiple optical transmission channels. Fiber optic routers can convert optical signals into data signals and perform data signal forwarding and routing. Fiber optic network interface cards (NICs) can be used in Ethernet networks to connect computers to optical fibers.

[0108] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0109] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0110] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0111] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0112] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0113] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0114] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical chip, characterized in that, It includes, from top to bottom, a lithium niobate layer, a buried oxide layer, and a substrate, wherein: An electro-optic modulator is provided in the lithium niobate layer; An integrated waveguide structure is provided in the buried oxide layer, and the electro-optic modulator is used to modulate the signal light transmitted in the integrated waveguide structure. The substrate is bonded to the buried oxide layer, and the substrate satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10; or resistance greater than or equal to 10 KΩ / cm.

2. The optical chip according to claim 1, characterized in that, in: The substrate is made of quartz; or The substrate is made of sapphire; or The substrate is made of silicon, and the resistivity of the silicon is greater than 10 kΩ / cm; or The substrate includes a trap-rich layer.

3. The optical chip according to claim 1 or 2, characterized in that, The bonding between the substrate and the buried oxide layer includes: The substrate and the buried oxide layer are directly bonded; or An adhesive layer is provided between the substrate and the buried oxide layer.

4. The optical chip according to any one of claims 1 to 3, characterized in that, The lithium niobate layer is bonded to the buried oxide layer.

5. The optical chip according to any one of claims 1 to 4, characterized in that, in: The buried oxygen layer further includes a first layer and / or a second layer; The first layer is composed of silicon dioxide, and the bonding between the substrate and the buried oxide layer includes: the substrate being bonded to the first layer; The second layer is composed of silicon dioxide, and the lithium niobate layer is bonded to the second layer.

6. The optical chip according to any one of claims 1 to 5, characterized in that, The optical chip is provided with a first coupler and a second coupler, wherein: The first coupler is used to receive a first signal light from the integrated waveguide and transmit the first signal light to the electro-optic modulator; The electro-optic modulator is used to modulate the first signal light to obtain the second signal light; The second coupler is used to receive the second signal light from the electro-optic modulator and transmit the second signal light to the integrated waveguide.

7. The optical chip according to any one of claims 1 to 6, characterized in that, The buried oxide layer includes a third layer and a fourth layer, wherein: The third layer is adjacent to the substrate, and the third layer includes a first waveguide and / or a second waveguide, wherein the first waveguide is used to receive a third signal light input to the optical chip, and the second waveguide is used to output a fourth signal light from the optical chip, and the first waveguide and the second waveguide are made of silicon material; The fourth layer is adjacent to the lithium niobate layer, and the fourth layer includes a polarization beam splitter and / or a polarization beam combiner made of silicon nitride material.

8. The optical chip according to claim 7, characterized in that, The optical chip further includes a third coupler and / or a fourth coupler, wherein: The third coupler is used to receive the fifth signal light from the third layer and send the fifth signal light to the fourth layer; The fourth coupler is used to receive the sixth signal light from the fourth layer and send the sixth signal light to the third layer.

9. An optical module, characterized in that, include: A light source, a signal generation chip, and an optical chip as described in any one of claims 1 to 8; and / or The signal processing chip is an optical chip as described in any one of claims 1 to 8.

10. An optical communication system, characterized in that, It includes optoelectronic devices and the optical module as described in claim 9, wherein the optoelectronic devices are connected to the optical module, and the optoelectronic devices are any one of optical switches, fiber optic routers, and fiber optic network cards.

11. A method for fabricating an optical chip, characterized in that, include: A buried oxide layer is fabricated on a silicon substrate, wherein an integrated waveguide structure is disposed in the buried oxide layer; The buried oxide layer and the lithium niobate layer are bonded together. An electro-optic modulator is disposed in the lithium niobate layer. The electro-optic modulator is used to modulate the signal light transmitted in the integrated waveguide structure. Remove the silicon substrate; The buried oxide layer and the first substrate are bonded together, wherein the first substrate satisfies at least one or more of the following conditions: dielectric constant less than or equal to 10, and resistance greater than or equal to 100 Ω / cm.

12. The method according to claim 11, characterized in that, Before removing the silicon substrate, the method further includes: bonding the lithium niobate layer and the second substrate; After removing the silicon substrate, the method further includes removing the second substrate.

13. The method according to claim 11, characterized in that, After removing the silicon substrate, the method further includes: Remove a first portion of the lithium niobate layer, wherein the first portion is the portion away from the buried oxide layer.

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