Optical module

Abstract

The invention provides an optical module which comprises an optical chip, an optical fiber and a waveguide coupler in coupling connection with the optical fiber, the waveguide coupler comprises a substrate, a first cladding and a second cladding which are arranged in the epitaxial growth direction, the refractive index of the substrate is larger than that of the second cladding, and the refractive index of the second cladding is larger than that of the first cladding; a first coupling waveguide, a second coupling waveguide and at least one transition waveguide located between the first coupling waveguide and the second coupling waveguide are arranged in the second cladding, the first coupling waveguide is in coupling connection with the optical fiber, and the gap between the first coupling waveguide and the transition waveguide is larger than that between the second coupling waveguide and the transition waveguide. The coincidence length between the first coupling waveguide and the transition waveguide is larger than the coincidence length between the second coupling waveguide and the transition waveguide, and an optical signal transmitted by the first coupling waveguide is coupled to the optical chip through at least one transition waveguide and the second coupling waveguide. According to the invention, the cladding with a low refractive index is additionally arranged between the coupling waveguide and the substrate, so that the leakage loss of the substrate is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of optical communication technology, and in particular to an optical module. Background Art

[0002] Optical communication technology is used in new services and application modes such as cloud computing, mobile Internet, and video. In optical communication, optical modules are devices that realize photoelectric signal conversion and are one of the key components in optical communication equipment. Among them, due to the advantages of optical chips such as small size, high integration density, and low cost, the use of optical chips to realize electro-optical-photoelectric conversion has become a mainstream solution for high-speed optical modules.

[0003] Optical chips need to be coupled with optical fibers to achieve the purpose of connecting to external optical paths. Common coupling methods include end-face coupling. When the optical chip is coupled with the optical fiber through an end-face coupler, due to the large refractive index difference between silicon and silicon dioxide or air, the silicon-based optical waveguide has a strong ability to limit the light field. The size of the silicon-based optical waveguide can be made very small, and its cross-sectional size is usually less than 0.5 microns, while the core diameter size of ordinary single-mode optical fibers is about 8-10 microns. The large difference between the two sizes causes serious mode field mismatch, resulting in large coupling losses.

[0004] Therefore, designing a method that can increase the mode field matching between silicon-based optical waveguides and single-mode optical fibers, thereby improving the coupling efficiency of the end coupler, is of great significance for silicon-based optoelectronic interconnection technology. Summary of the invention

[0005] The embodiments of the present disclosure provide an optical module to solve the defect of large coupling loss between silicon-based optical waveguide and single-mode optical fiber, and achieve ultra-low coupling insertion loss between silicon-based optical waveguide and single-mode optical fiber.

[0006] In a first aspect, the present disclosure provides an optical module, comprising:

[0007] Circuit boards;

[0008] An optical chip, electrically connected to the circuit board, and used for receiving an external optical signal;

[0009] An optical fiber, used for transmitting the external optical signal;

[0010] A waveguide coupler is coupled to the optical fiber, and is used to couple an external optical signal transmitted by the optical fiber to the optical chip; wherein the waveguide coupler includes:

[0011] substrate;

[0012] A first cladding layer is arranged on the substrate along the epitaxial growth direction;

[0013] A second cladding layer is arranged on the first cladding layer along the epitaxial growth direction, the refractive index of the substrate is greater than the refractive index of the second cladding layer, and the refractive index of the second cladding layer is greater than the refractive index of the first cladding layer;

[0014] a first coupling waveguide, located in the second cladding, one end of the first coupling waveguide being coupled to the optical fiber, and the first coupling waveguide being used to receive an external optical signal transmitted by the optical fiber;

[0015] A second coupling waveguide, located in the second cladding, the second coupling waveguide being used to couple the external optical signal to the optical chip;

[0016] at least one transition waveguide is located between the first coupling waveguide and the second coupling waveguide, a first gap is provided between the first coupling waveguide and the at least one transition waveguide, a first overlapping portion is provided between the first coupling waveguide and the at least one transition waveguide, a second gap is provided between the second coupling waveguide and the at least one transition waveguide, a second overlapping portion is provided between the second coupling waveguide and the at least one transition waveguide, the second gap is smaller than the first gap, a length of the second overlapping portion is smaller than a length of the first overlapping portion, and the at least one transition waveguide is used to couple an external optical signal transmitted by the first coupling waveguide to the second coupling waveguide.

[0017] In a second aspect, the present disclosure provides an optical module, including:

[0018] Circuit boards;

[0019] An optical chip, electrically connected to the circuit board, and used for receiving an external optical signal;

[0020] An optical fiber, used for transmitting the external optical signal;

[0021] A waveguide coupler is coupled to the optical fiber, and the waveguide coupler is used to transmit an optical signal to the optical chip; wherein the waveguide coupler includes:

[0022] substrate;

[0023] A first cladding layer is disposed on the substrate;

[0024] A second cladding layer is disposed on the first cladding layer, the refractive index of the substrate is greater than the refractive index of the second cladding layer, and the refractive index of the second cladding layer is greater than the refractive index of the first cladding layer;

[0025] a first coupling waveguide, located in the second cladding, the first coupling waveguide comprising a first tapered waveguide and a second tapered waveguide connected to each other, the tip of the first tapered waveguide being coupled to the optical fiber, and the first coupling waveguide being used to receive an optical signal transmitted by the optical fiber;

[0026] A second coupling waveguide is located in the second cladding, the second coupling waveguide includes a seventh tapered waveguide connected to a straight waveguide, the straight waveguide is adjacent to the optical chip, and the second coupling waveguide is used to couple the optical signal to the optical chip;

[0027] at least one transition waveguide, located between the first coupling waveguide and the second coupling waveguide, a first overlapped portion between the tapered waveguide of the at least one transition waveguide facing the second tapered waveguide and the second tapered waveguide, a second overlapped portion between the tapered waveguide of the at least one transition waveguide facing the seventh tapered waveguide and the seventh tapered waveguide, a length of the second overlapped portion being shorter than a length of the first overlapped portion, and the at least one transition waveguide being used to couple an external optical signal transmitted by the first coupling waveguide to the second coupling waveguide;

[0028] The side grooves are located in the first cladding layer and the second cladding layer, and the side grooves are located on both sides of the first coupling waveguide and the second coupling waveguide.

[0029] As can be seen from the above embodiments, the optical module provided by the embodiments of the present disclosure includes a circuit board, an optical chip, an optical fiber and a waveguide coupler. The optical chip is electrically connected to the circuit board, the waveguide coupler is coupled to the optical fiber, the waveguide coupler is optically connected to the optical chip, and the optical signal transmitted by the optical fiber is coupled to the optical chip via the waveguide coupler. The optical chip converts the optical signal into an electrical signal to achieve light reception. The waveguide coupler includes a substrate, a first cladding, a second cladding, a first coupling waveguide, a second coupling waveguide and at least one transition waveguide. The first cladding is arranged on the substrate along the epitaxial growth direction, and the second cladding is arranged on the first cladding along the epitaxial growth direction, so that the substrate, the first cladding and the second cladding are arranged in sequence along the epitaxial growth direction, and the refractive index of the substrate is greater than the refractive index of the second cladding, and the refractive index of the second cladding is greater than the refractive index of the first cladding; the first coupling waveguide, the second coupling waveguide and at least one transition waveguide are located in the second cladding, one end of the first coupling waveguide is coupled to the optical fiber, and the first coupling waveguide is used to receive an external optical signal transmitted by the optical fiber; at least one transition waveguide is located between the first coupling waveguide and the second coupling waveguide. At least one transition waveguide is used to couple the optical signal transmitted by the first coupling waveguide to the second coupling waveguide, and the second coupling waveguide couples the optical signal to the optical chip to realize light reception; wherein, there is a first gap between the first coupling waveguide and the at least one transition waveguide, there is a first overlapped portion between the first coupling waveguide and the at least one transition waveguide, there is a second gap between the second coupling waveguide and the at least one transition waveguide, there is a second overlapped portion between the second coupling waveguide and the at least one transition waveguide, the second gap is smaller than the first gap, and the length of the second overlapped portion is smaller than the length of the first overlapped portion, so as to realize the coupling connection between the first coupling waveguide and the second coupling waveguide through at least one transition waveguide. When the optical signal is gradually coupled from the first coupling waveguide to the second coupling waveguide through at least one transition waveguide, the optical signal may leak into the second cladding. Since the refractive index of the first cladding is smaller than the refractive index of the second cladding and the substrate, the optical signal transmitted by the waveguide is difficult to leak from the second cladding with a high refractive index to the first cladding with a low refractive index, which can reduce the leakage of light to the substrate, thereby reducing the substrate leakage loss of the waveguide.

[0030] The present invention adopts a first cladding and a second cladding with different refractive indices, and a coupling waveguide and a transition waveguide are located in the second cladding. Light transmission is achieved through the gap between the coupling waveguide and the transition waveguide and the length of the overlapping part, so that the light transmitted by the optical fiber is coupled to the optical chip via the waveguide coupler, which can improve the light coupling efficiency; the first cladding is located between the second cladding and the substrate, and the second cladding is supported by the first cladding, which can avoid the use of a substrate hollowing process and enhance the structural strength of the waveguide coupler. At the same time, since the refractive index of the first cladding is lower than the refractive index of the substrate, it can avoid the light in the waveguide and the second cladding from entering the first cladding with a low refractive index, which can reduce the light transmission to the substrate, and can reduce the substrate leakage loss of the waveguide, so as to achieve ultra-low coupling insertion loss with the single-mode optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the present disclosure, the following briefly introduces the drawings required to be used in some embodiments of the present disclosure. Obviously, the drawings described below are only drawings of some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can also be obtained based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams, and are not intended to limit the actual size of the product involved in the embodiments of the present disclosure, the actual process of the method, the actual timing of the signal, etc.

[0032] Figure 1 A partial structural diagram of an optical communication system provided according to some embodiments of the present disclosure;

[0033] Figure 2 A partial structural diagram of a host computer provided according to some embodiments of the present disclosure;

[0034] Figure 3 A structural diagram of an optical module provided according to some embodiments of the present disclosure;

[0035] Figure 4 An exploded view of an optical module provided according to some embodiments of the present disclosure;

[0036] Figure 5 A partial structural diagram of an optical module provided according to some embodiments of the present disclosure;

[0037] Figure 6 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 1 ;

[0038] Figure 7 A top view of an end face coupler in an optical module provided according to some embodiments of the present disclosure;

[0039] Figure 8 for Figure 7 Middle AA section view;

[0040] Fig. 9 for Figure 7 Middle BB section view;

[0041] Fig.10 for Figure 7 Middle CC section view;

[0042] Fig.11 for Figure 7 Middle DD section view;

[0043] Fig.12 for Figure 7 Middle EE section view;

[0044] Fig.13 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 2 ;

[0045] Fig.14 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 3 ;

[0046] Fig.15 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 4 ;

[0047] Fig.16 It is a longitudinal cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0048] The following will be combined with the accompanying drawings to clearly and in detail describe the technical solutions in some embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present disclosure.

[0049] In optical communication technology, in order to establish information transmission between information processing devices, it is necessary to load information onto light and use the propagation of light to achieve information transmission. Here, the light loaded with information is an optical signal. When optical signals are transmitted in information transmission equipment, the loss of optical power can be reduced, so high-speed, long-distance, and low-cost information transmission can be achieved. The signals that information processing equipment can recognize and process are electrical signals. Information processing equipment usually includes optical network terminals (Optical Network Unit, ONU), gateways, routers, switches, mobile phones, computers, servers, tablets, televisions, etc., and information transmission equipment usually includes optical fibers and optical waveguides.

[0050] The optical module can realize the mutual conversion between optical signals and electrical signals between information processing equipment and information transmission equipment. For example, at least one of the optical signal input end or the optical signal output end of the optical module is connected to an optical fiber, and at least one of the electrical signal input end or the electrical signal output end of the optical module is connected to an optical network terminal; the first optical signal from the optical fiber is transmitted to the optical module, and the optical module converts the first optical signal into a first electrical signal, and transmits the first electrical signal to the optical network terminal; the second electrical signal from the optical network terminal is transmitted to the optical module, and the optical module converts the second electrical signal into a second optical signal, and transmits the second optical signal to the optical fiber. Since multiple information processing devices can transmit information through electrical signals, at least one of the multiple information processing devices needs to be directly connected to the optical module, and all information processing devices do not need to be directly connected to the optical module. Here, the information processing device directly connected to the optical module is called the upper computer of the optical module. In addition, the optical signal input end or the optical signal output end of the optical module can be called an optical port, and the electrical signal input end or the electrical signal output end of the optical module can be called an electrical port.

[0051] Figure 1 FIG. 1 is a partial structural diagram of an optical communication system provided according to some embodiments of the present disclosure. Figure 1 As shown, the optical communication system mainly includes a remote information processing device 1000 , a local information processing device 2000 , a host computer 100 , an optical module 200 , an optical fiber 101 and a network cable 103 .

[0052] One end of the optical fiber 101 extends toward the remote information processing device 1000, and the other end of the optical fiber 101 is connected to the optical module 200 through the optical port of the optical module 200. The optical signal can be totally reflected in the optical fiber 101, and the propagation of the optical signal in the total reflection direction can almost maintain the original optical power. The optical signal undergoes multiple total reflections in the optical fiber 101 to transmit the optical signal from the remote information processing device 1000 to the optical module 200, or to transmit the optical signal from the optical module 200 to the remote information processing device 1000, thereby realizing long-distance, low-power loss information transmission.

[0053] The optical communication system may include one or more optical fibers 101, and the optical fibers 101 are detachably connected or fixedly connected to the optical module 200. The host computer 100 is configured to provide data signals to the optical module 200, receive data signals from the optical module 200, or monitor or control the working state of the optical module 200.

[0054] The host computer 100 includes a substantially rectangular housing and an optical module interface 102 disposed on the housing. The optical module interface 102 is configured to connect to the optical module 200 so that the host computer 100 and the optical module 200 establish a unidirectional or bidirectional electrical signal connection.

[0055] The host computer 100 also includes an external electrical interface, which can be connected to an electrical signal network. For example, the external electrical interface includes a Universal Serial Bus (USB) interface or a network cable interface 104, and the network cable interface 104 is configured to access the network cable 103 so that the host computer 100 establishes a unidirectional or bidirectional electrical signal connection with the network cable 103. One end of the network cable 103 is connected to the local information processing device 2000, and the other end of the network cable 103 is connected to the host computer 100, so as to establish an electrical signal connection between the local information processing device 2000 and the host computer 100 through the network cable 103. For example, the third electrical signal sent by the local information processing device 2000 is transmitted to the host computer 100 through the network cable 103, and the host computer 100 generates a second electrical signal according to the third electrical signal. The second electrical signal from the host computer 100 is transmitted to the optical module 200, and the optical module 200 converts the second electrical signal into a second optical signal, and transmits the second optical signal to the optical fiber 101, and the second optical signal is transmitted to the remote information processing device 1000 in the optical fiber 101. For example, the first optical signal from the remote information processing device 1000 is transmitted through the optical fiber 101, and the first optical signal from the optical fiber 101 is transmitted to the optical module 200, and the optical module 200 converts the first optical signal into a first electrical signal, and the optical module 200 transmits the first electrical signal to the host computer 100, and the host computer 100 generates a fourth electrical signal according to the first electrical signal, and transmits the fourth electrical signal to the local information processing device 2000. It should be noted that the optical module is a tool for realizing the mutual conversion between optical signals and electrical signals. During the conversion process between the optical signals and electrical signals, the information does not change, but the encoding and decoding methods of the information can change.

[0056] In addition to the optical network terminal, the host computer 100 also includes an optical line terminal (OLT), an optical network device (ONT), or a data center server.

[0057] Figure 2 1 is a partial structural diagram of a host computer provided according to some embodiments of the present disclosure. In order to clearly show the connection relationship between the optical module 200 and the host computer 100, Figure 2 Only the structure of the host computer 100 related to the optical module 200 is shown. Figure 2 As shown, the host computer 100 further includes a PCB circuit board 105 disposed in the housing, a cage 106 disposed on the surface of the PCB circuit board 105, a heat sink 107 disposed on the cage 106, and an electrical connector disposed inside the cage 106. The electrical connector is configured to access the electrical port of the optical module 200; the heat sink 107 has a protruding structure such as fins to increase the heat dissipation area.

[0058] The optical module 200 is inserted into the cage 106 of the host computer 100, and the cage 106 fixes the optical module 200. The heat generated by the optical module 200 is transferred to the cage 106 and then diffused through the heat sink 107. After the optical module 200 is inserted into the cage 106, the electrical port of the optical module 200 is connected to the electrical connector inside the cage 106, so that the optical module 200 establishes a bidirectional electrical signal connection with the host computer 100. In addition, the optical port of the optical module 200 is connected to the optical fiber 101, so that the optical module 200 establishes a bidirectional optical signal connection with the optical fiber 101.

[0059] Figure 3 is a structural diagram of an optical module provided according to some embodiments of the present disclosure, Figure 4 FIG. 1 is an exploded view of an optical module provided according to some embodiments of the present disclosure. Figure 3 and Figure 4 As shown, the optical module 200 includes a shell, a circuit board 300 disposed in the shell, a light source 900, an optical chip 1100, an optical fiber adapter 700, and an optical fiber connecting the optical chip 1100 and the optical fiber adapter 700, but the present disclosure is not limited thereto.

[0060] The housing comprises an upper housing 201 and a lower housing 202 . The upper housing 201 covers the lower housing 202 to form the housing having two openings 204 and 205 . The outer contour of the housing is generally a square body.

[0061] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 located on both sides of the bottom plate 2021 and arranged perpendicular to the bottom plate 2021; the upper shell 201 includes a cover plate 2011, and the cover plate 2011 covers the two lower side plates 2022 of the lower shell 202 to form the above-mentioned shell.

[0062] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 located on both sides of the bottom plate 2021 and vertically arranged with the bottom plate 2021; the upper shell 201 includes a cover plate 2011 and two upper side plates located on both sides of the cover plate 2011 and vertically arranged with the cover plate 2011, and the two upper side plates are combined with the two lower side plates 2022 to realize that the upper shell 201 covers the lower shell 202.

[0063] The direction of the line connecting the two openings 204 and 205 may be consistent with the length direction of the optical module 200, or may be inconsistent with the length direction of the optical module 200. For example, the opening 204 is located at the end of the optical module 200 ( Figure 3 The opening 205 is also located at the end of the optical module 200 ( Figure 3Alternatively, the opening 204 is located at the end of the optical module 200, and the opening 205 is located at the side of the optical module 200. The opening 204 is an electrical port, and the gold finger of the circuit board 300 extends from the electrical port and is inserted into the electrical connector of the host computer 100; the opening 205 is an optical port, which is configured to access the external optical fiber 101 so that the optical fiber 101 is connected to the optical transceiver component 900 in the optical module 200.

[0064] The assembly method of combining the upper housing 201 and the lower housing 202 is adopted, so that the circuit board 300, the light source 900, the optical chip 1100, the optical fiber adapter 700, and the optical fiber connecting the optical chip 1100 and the optical fiber adapter 700 are conveniently installed in the above housing, and the above components can be encapsulated and protected by the upper housing 201 and the lower housing 202. In addition, when assembling the circuit board 300, the light source 900, the optical chip 1100, the optical fiber adapter 700, and the optical fiber connecting the optical chip 1100 and the optical fiber adapter 700, the assembly method of the upper housing 201 and the lower housing 202 is adopted, so that the positioning components, heat dissipation components, and electromagnetic shielding components of these components are conveniently arranged, which is conducive to the automated production.

[0065] In some embodiments, the upper shell 201 and the lower shell 202 are made of metal materials to facilitate electromagnetic shielding and heat dissipation.

[0066] In some embodiments, the optical module 200 further includes an unlocking component 600 located outside its housing. The unlocking component 600 is configured to achieve a fixed connection between the optical module 200 and the host computer 100, or to release the fixed connection between the optical module 200 and the host computer 100.

[0067] For example, the unlocking component 600 is located on the outside of the two lower side plates 2022 of the lower housing 202, and includes a snap-fit ​​component that matches the cage 106 of the host computer 100. When the optical module 200 is inserted into the cage 106, the snap-fit ​​component of the unlocking component 600 fixes the optical module 200 in the cage 106; when the unlocking component 600 is pulled, the snap-fit ​​component of the unlocking component 600 moves accordingly, thereby changing the connection relationship between the snap-fit ​​component and the host computer, so as to release the fixation of the optical module 200 and the host computer, so that the optical module 200 can be pulled out of the cage 106.

[0068] The circuit board 300 includes circuit traces, electronic components and chips, etc. The electronic components and chips are connected according to the circuit design through the circuit traces to realize the functions of power supply, electrical signal transmission and grounding. The electronic components may include capacitors, resistors, transistors, metal-oxide-semiconductor field-effect transistors (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET). The chip may include a microcontroller unit (Microcontroller Unit, MCU), a laser driver chip, a transimpedance amplifier (Transimpedance Amplifier, TIA), a limiting amplifier (Limiting Amplifier, LA), a clock and data recovery chip (Clock and Data Recovery, CDR), a power management chip, and a digital signal processing (Digital Signal Processing, DSP) chip.

[0069] The circuit board 300 is generally a rigid circuit board. Due to its relatively hard material, the rigid circuit board can also realize the load-bearing function. For example, the rigid circuit board can stably carry the above-mentioned electronic components and chips; the rigid circuit board can also be inserted into the electrical connector in the cage 106 of the host computer 100.

[0070] The circuit board 300 also includes a gold finger formed on the end surface thereof, and the gold finger is composed of a plurality of independent pins. The circuit board 300 is inserted into the cage 106, and the gold finger is connected to the electrical connector in the cage 106. The gold finger can be provided on the surface of only one side of the circuit board 300 (for example, Figure 4 The upper surface shown in the figure) can also be set on the upper and lower surfaces of the circuit board 300 to provide a larger number of pins, so as to adapt to occasions where the number of pins is large. The gold finger is configured to establish an electrical connection with the host computer to achieve power supply, grounding, two-wire synchronous serial (Inter-Integrated Circuit, I2C) signal transmission, data signal transmission, etc. Of course, flexible circuit boards are also used in some optical modules. Flexible circuit boards are generally used in conjunction with rigid circuit boards to supplement rigid circuit boards.

[0071] In some embodiments, the light source 900 and the optical chip 1100 are physically separated from the circuit board 300 and then electrically connected to the circuit board 300 through a flexible circuit board or an electrical connector.

[0072] In some embodiments, the light source 900 and the optical chip 1100 may be directly disposed on the circuit board 300. For example, the light source 900 and the optical chip 1100 may be disposed on the surface of the circuit board 300 or on the side of the circuit board 300.

[0073] Figure 5 FIG. 1 is a partial structural diagram of an optical module provided according to some embodiments of the present disclosure. Figure 5 As shown, the optical chip 1100 is disposed on the circuit board 300, and the optical chip 1100 is electrically connected to the circuit board 300. For example, the optical chip 1100 is electrically connected to the circuit board 300 by wire bonding, and the periphery of the optical chip 1100 is connected to the circuit board 300 through multiple conductive wires. Therefore, the optical chip 1100 is generally disposed on the surface of the circuit board 300.

[0074] The optical chip 1100 and the light source 900 can be optically connected via a first optical fiber ribbon, and the optical chip 1100 receives light from the light source 900 via the optical fiber ribbon, and the optical chip 1100 modulates the light; end-face coupling can also be directly achieved between the optical chip 1100 and the light source 900, and the optical chip 1100 directly receives light from the light source 900, and the optical chip 1100 modulates the light.

[0075] The optical chip 1100 and the optical fiber adapter 700 can be optically connected through the transmitting optical fiber and the receiving optical fiber, and the optical fiber adapter 700 can realize the optical connection with the external optical fiber of the optical module. The light modulated by the optical chip 1100 is transmitted to the optical fiber adapter 700 through the transmitting optical fiber, and then transmitted to the external optical fiber through the optical fiber adapter 700 to realize the emission of light; the light transmitted by the external optical fiber is transmitted to the receiving optical fiber through the optical fiber adapter 700, and then transmitted to the optical chip 1100 through the receiving optical fiber, and the optical chip 1100 converts the received optical signal into an electrical signal to realize the reception of light.

[0076] In some embodiments, the optical chip 1100 is a silicon photonic chip, which is provided with an input optical port, an output optical port, a monitoring optical port, a high-speed electrical signal interface, and a DC bias signal interface, etc., wherein the input optical port includes a first input optical port and a second input optical port, the first input optical port is used to couple the light output by the light source 900 into the silicon photonic chip, the second input optical port is used to couple the signal light transmitted by the optical fiber outside the optical module into the silicon photonic chip, and the output optical port is used to couple the signal light modulated by the silicon photonic chip out of the optical chip 1100.

[0077] When the optical chip 1100 is coupled with the transmitting optical fiber and the receiving optical fiber, common coupling methods include end-face coupling and grating coupling. Among them, the grating coupling method is easy to process and has a larger light spot, but it has limitations such as large insertion loss and wavelength sensitivity. In the end-face coupling method, due to the large refractive index difference between silicon and silicon dioxide or air, the silicon waveguide has a strong ability to limit the light field. The size of the silicon waveguide can be made into a very small size, and its cross-sectional size is usually less than 0.5 microns, while the core diameter size of an ordinary single-mode optical fiber is about 8-10 microns. The size difference between the two is very large, resulting in serious mode field mismatch, which leads to large coupling loss.

[0078] Traditional end-face couplers (Spot Size Converter, SSC) need to prevent light from leaking to the silicon wafer substrate, usually requiring a substrate hollowing process to form a suspended waveguide structure, which often has greater reliability risks than solid waveguide structures. A common solid SSC design idea is to slightly reduce the mode spot to about 6μm, which can effectively reduce substrate leakage loss, but compared with the standard single-mode fiber mode spot size (9-10μm), there is still a large mode mismatch loss of about 1dB.

[0079] In order to solve the above problems, the present disclosure provides an optical module, which proposes a low-loss solid large-mode spot SSC design, which can avoid the use of a substrate hollowing process and enhance the installation reliability of the waveguide. At the same time, the multi-layer cladding oxide structure design with different refractive indices can further reduce the substrate leakage loss of the solid waveguide and achieve ultra-low coupling insertion loss with a standard single-mode optical fiber.

[0080] Figure 6 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 1 .like Figure 5 and Figure 6 As shown, the optical module provided by the embodiment of the present disclosure also includes a waveguide coupler 1200, which is an end face coupler. The waveguide coupler 1200 is located between the optical chip 1100 and the transmitting optical fiber, and between the optical chip 1100 and the receiving optical fiber. The waveguide coupler 1200 is used to realize the coupling connection between the optical chip 1100 and the transmitting optical fiber, so as to couple the signal light modulated by the optical chip 1100 to the transmitting optical fiber through the waveguide coupler 1200 to realize the emission of the modulated light; and, the signal light transmitted by the receiving optical fiber is coupled to the optical chip 1100 through the waveguide coupler 1200 to realize the reception of light.

[0081] Among them, the waveguide coupler 1200 includes a substrate 1201, a first cladding 1202 and a second cladding 1203. Along the epitaxial growth direction, the first cladding 1202 is arranged on the substrate 1201, and the second cladding 1203 is arranged on the first cladding 1202, so that the substrate 1201, the first cladding 1202 and the second cladding 1203 are arranged in sequence along the epitaxial growth direction.

[0082] In some embodiments, the substrate 1201 is a silicon-on-insulator (SOI) substrate. The SOI substrate is a substrate commonly used for silicon-based devices. The SOI substrate generally includes a silicon substrate and a buried oxide layer disposed on the silicon substrate. The thickness of the buried oxide layer is generally 3 μm. It should be noted that a complete SOI substrate generally also includes a top layer of silicon disposed on the buried oxide layer. The thickness of the top layer of silicon is generally 220 nm. However, when preparing the end face coupler, in order to prevent light from being drawn into the top layer of silicon, the top layer of silicon is removed to leak out of the buried oxide layer, and then corresponding processing is performed on the buried oxide layer.

[0083] The first cladding layer 1202 is disposed on a side of the buried oxide layer opposite to the silicon substrate. The first cladding layer 1202 may be a silicon dioxide cladding layer. The refractive index of the first cladding layer 1202 is smaller than the refractive index of the substrate 1201 .

[0084] The second cladding 1203 is disposed on a side of the first cladding 1202 opposite to the substrate 1201, so as to support the second cladding 1203 through the first cladding 1202. The second cladding 1203 may be a silicon nitride cladding, and the refractive index of the second cladding 1203 is greater than the refractive index of the first cladding 1202. In this way, along the epitaxial growth direction, the refraction of the waveguide coupler 1200 first decreases and then increases, so that better longitudinal constraints on the light field can be formed to prevent the light in the second cladding 1203 from leaking into the substrate 1201.

[0085] In some embodiments, the thickness of the first cladding 1202 is a first thickness H1, and the thickness of the second cladding 1203 is a second thickness H2. The second thickness H2 is greater than the first thickness H1 to facilitate the arrangement of a coupling waveguide in the second cladding 1203.

[0086] In some embodiments, the first thickness H1 has a size ranging from 2 to 3 μm, and the second thickness H2 has a size ranging from 6 to 10 μm.

[0087] The second cladding 1203 has a first end face 1208 optically coupled to the optical fiber and a second end face 1209 optically coupled to the optical chip 1100. A coupling waveguide may be provided in the second cladding 1203, one end of the coupling waveguide being adjacent to the first end face 1208, and the other end of the coupling waveguide being adjacent to the second end face 1209, so that one end of the coupling waveguide is coupled to the optical fiber to receive an optical signal, and the coupling waveguide can directionally transmit the optical signal along its own extension direction, and the coupling waveguide couples the transmitted optical signal to the optical chip 1100, thereby realizing the coupling connection between the optical chip 1100 and the optical fiber through the coupling waveguide.

[0088] The coupling waveguide may be a tapered waveguide, the end of the coupling waveguide used for coupling the optical fiber is called the tip, and the end of the coupling waveguide used for connecting the optical chip 1100 is called the end, the tip is smaller in size to match the mode field of the optical fiber, and the end is larger in size to match the optical chip 1100. In the actual design process, the widths of the tip and the end and the overall thickness of the coupling waveguide may be designed according to actual needs.

[0089] The coupling waveguides in the second cladding 1203 include a first coupling waveguide 1204 and a second coupling waveguide 1205. One end of the first coupling waveguide 1204 is close to the first end face 1208, so that the first coupling waveguide 1204 is coupled and connected to the optical fiber, and the first coupling waveguide 1204 is used to confine the light transmitted by the optical fiber to a mode field of a predetermined size; one end of the second coupling waveguide 1205 is close to the second end face 1209, so that the second coupling waveguide 1205 is optically connected to the optical chip 1100, and the second coupling waveguide 1205 is used to couple the light confined in the predetermined mode field by the first coupling waveguide 1204 into the optical chip 1100; the first coupling waveguide 1204 and the second coupling waveguide 1205 are coupled and connected, thereby realizing optical coupling between the optical fiber and the optical chip 1100 through the first coupling waveguide 1204 and the second coupling waveguide 1205.

[0090] In some embodiments, when the waveguide coupler 1200 realizes the coupling connection between the optical fiber and the optical chip 1100 through the first coupling waveguide 1204 and the second coupling waveguide 1205, the position of the first coupling waveguide 1204 in the second cladding 1203 needs to correspond to the optical fiber. When the gap between the first coupling waveguide 1204 and the second coupling waveguide 1205 exceeds the preset range, that is, when the position of the optical fiber is higher, the first coupling waveguide 1204 is far away from the substrate 1201, which will affect the coupling efficiency of the first coupling waveguide 1204 and the second coupling waveguide 1205. In order to improve the coupling efficiency of the first coupling waveguide 1204 and the second coupling waveguide 1205, a transition waveguide can be set between the first coupling waveguide 1204 and the second coupling waveguide 1205, and the light field with a higher end face in the waveguide coupler 1200 is transitioned layer by layer to the lower waveguide through the transition waveguide, and finally reaches the coupling waveguide closer to the substrate 1201.

[0091] The waveguide coupler 1200 includes at least one transition waveguide, wherein the at least one transition waveguide is located between a first coupling waveguide 1204 and a second coupling waveguide 1205, a first gap is provided between the first coupling waveguide 1204 and the at least one transition waveguide, and a second gap is provided between the second coupling waveguide 1205 and the at least one transition waveguide.

[0092] Since the larger the gap between the waveguides, the greater the coupling difficulty, therefore, in order to reduce the coupling difficulty of the first coupling waveguide 1204, the at least one transition waveguide and the second coupling waveguide 1205, the second gap G2 is smaller than the first gap G1, so that the higher light field at the first end face 1208 is gradually transitioned to the at least one transition waveguide through the first coupling waveguide 1204, and finally reaches the second coupling waveguide 1205, and in the process of light field transition, the light field in the second cladding 1203 is prevented from leaking to the substrate 1201.

[0093] In order to couple the optical signal transmitted by the first coupling waveguide 1204 into at least one transition waveguide, and couple the optical signal transmitted by at least one transition waveguide into the second coupling waveguide 1205, a first overlapping portion is provided between the first coupling waveguide 1204 and at least one transition waveguide, and a second overlapping portion is provided between the second coupling waveguide 1205 and at least one transition waveguide, and the length of the second overlapping portion is smaller than the length of the first overlapping portion, so as to ensure the coupling efficiency among the first coupling waveguide 1204, at least one transition waveguide and the second coupling waveguide 1205, and reduce the leakage of the optical field in the second cladding 1203 to the substrate 1201.

[0094] Reference Figure 6 In some embodiments, the waveguide coupler 1200 may include a first transition waveguide 1206 and a second transition waveguide 1207. The first transition waveguide 1206 and the second transition waveguide 1207 are located in the second cladding 1203. Along the epitaxial growth direction, the first transition waveguide 1206 is located between the first coupling waveguide 1204 and the second coupling waveguide 1205. The second transition waveguide 1207 is located between the first transition waveguide 1206 and the second coupling waveguide 1205. One end of the first coupling waveguide 1204 is coupled to the optical fiber. The other end of 1204 is coupled and connected to one end of the first transition waveguide 1206, the other end of the first transition waveguide 1206 is coupled and connected to one end of the second transition waveguide 1207, the other end of the second transition waveguide 1207 is coupled and connected to one end of the second coupling waveguide 1205, and the other end of the second coupling waveguide 1205 is optically connected to the optical chip 1100, so as to realize the coupling connection between the optical fiber and the optical chip 1100 through the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205.

[0095] In some embodiments, the second transition waveguide 1207 has a third height H3 with the upper surface of the substrate 1201, the first transition waveguide 1206 has a fourth height H4 with the upper surface of the substrate 1201, the first coupling waveguide 1204 has a fifth height H5 with the upper surface of the substrate 1201, the second coupling waveguide 1205 is adjacent to the first cladding 1202, the fifth height H5 is greater than the fourth height H4, and the fourth height H4 is greater than the third height H3.

[0096] There is a first gap G1 between the first coupling waveguide 1204 and the first transition waveguide 1206, a second gap G2 between the second coupling waveguide 1205 and the second transition waveguide 1207, and a third gap G3 between the first transition waveguide 1206 and the second transition waveguide 1207. Since the larger the gap between the waveguides, the greater the coupling difficulty, in order to reduce the coupling difficulty between the first coupling waveguide 1204 and the first transition waveguide 1206, the first transition waveguide 1206 and the second transition waveguide 1207, and the second transition waveguide 1207 and the second coupling waveguide 1205, the first gap G1 is greater than the second gap G2, and the third gap G3 is greater than the second gap G2, so that the higher light field at the first end face 1208 is gradually transitioned to the first transition waveguide 1206 and the second transition waveguide 1207, and finally reaches the second coupling waveguide 1205, and in the process of light field transition, the light field in the second cladding 1203 is prevented from leaking to the substrate 1201.

[0097] In some embodiments, the size range of the third height H3 is 2 to 4 μm, the size range of the fourth height H4 is 3 to 6 μm, the size range of the fifth height H5 is 3 to 6 μm, the size range of the first gap G1 is 0.5 to 2 μm, the size range of the second gap G2 is 0.1 to 0.8 μm, and the size range of the third gap G3 is 0.5 to 2 μm.

[0098] In some embodiments, the first gap G1 may be larger than the third gap G3, so that the first gap G1, the third gap G3 and the second gap G2 gradually decrease, that is, along the light receiving direction, the gap between the waveguides in the waveguide coupler 1200 gradually decreases.

[0099] In some embodiments, the first gap G1 may also be smaller than the third gap G3 , and the first gap G1 may be larger than the second gap G2 , so that there is no regularity among the first gap G1 , the third gap G3 , and the second gap G2 .

[0100] In some embodiments, in order to improve the coupling efficiency between waveguides, the larger the gap between the waveguides, the longer the overlapping length between the waveguides. Thus, the size of the first gap G1 is 1.3 μm, and the length of the first overlapping portion between the first coupling waveguide 1204 and the first transition waveguide 1206 is 400 μm; the size of the second gap G2 is 0.43 μm, and the length of the second overlapping portion between the second coupling waveguide 1205 and the second transition waveguide 1207 is 100 μm; the size of the third gap is 0.85 μm, and the length of the third overlapping portion between the first transition waveguide 1206 and the second transition waveguide 1207 is 200 μm.

[0101] In some embodiments, the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 are supported on the second cladding 1203 through the first cladding 1202 located therebelow, and are supported on the substrate 1201 through the second cladding 1203, that is, the second cladding 1203 covering the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 is supported on the substrate 1201 through the first cladding 1202, so that the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 can be effectively supported by the substrate 1201, avoiding the use of a substrate hollowing process, and enhancing the installation reliability of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205.

[0102] Since the refractive index of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 is greater than the refractive index of the second cladding 1203, and the refractive index of the second cladding 1203 is greater than the refractive index of the first cladding 1202, the light transmitted by the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 is difficult to leak from the second cladding 1203 to the first cladding 1202, thereby reducing the leakage of the optical signal into the substrate 1201, thereby reducing the substrate leakage loss of the coupling waveguide, which is beneficial to improving the optical signal coupling efficiency from the optical fiber to the optical chip 1100.

[0103] Figure 7 FIG. 1 is a top view of an end face coupler in an optical module provided according to some embodiments of the present disclosure. Figure 7 As shown, in order to facilitate the matching of the mode field of the first coupling waveguide 1204 and the optical fiber, the modes of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 are matched, and the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 adopt a tapered structure.

[0104] The first coupling waveguide 1204 includes a first tapered waveguide 1220 and a second tapered waveguide 1221. The tip of the first tapered waveguide 1220 is adjacent to the first end face 1208, and the tip of the second tapered waveguide 1221 is opposite to the tip of the first tapered waveguide 1220, that is, the tip of the first tapered waveguide 1220 is adjacent to the first end face 1208, and the tip of the second tapered waveguide 1221 is away from the first end face 1208.

[0105] In some embodiments, the tip of the first tapered waveguide 1220 is coupled to a transmitting optical fiber or a receiving optical fiber, and the width of the tip is small, so that the light mode at the tip is distributed into the second cladding 1203, so as to better match the light mode transmitted by the externally coupled optical fiber, that is, the light field distribution at the tip has a better overlap with the light field distribution in the optical fiber and a higher coupling efficiency.

[0106] In some embodiments, the end of the first tapered waveguide 1220 can be directly connected to the end of the second tapered waveguide 1221, and the width of the end is greater than the width of the tip, so that the refractive index of the end is greater than the refractive index of the tip to facilitate coupling of light from the tip to the end.

[0107] In some embodiments, the first coupling waveguide 1204 may further include a straight waveguide, which connects the first tapered waveguide 1220 and the second tapered waveguide 1221. The width of the straight waveguide is the same as the width of the ends of the first tapered waveguide 1220 and the second tapered waveguide 1221, that is, the end of the first tapered waveguide 1220 is connected to one end of the straight waveguide, and the end of the second tapered waveguide 1221 is connected to the other end of the straight waveguide, so that the first tapered waveguide 1220 and the second tapered waveguide 1221 are connected through the straight waveguide in the middle.

[0108] The first transition waveguide 1206 includes a third tapered waveguide 1240 and a fourth tapered waveguide 1241 connected to each other. The tip of the third tapered waveguide 1240 faces the second tapered waveguide 1221 . The third tapered waveguide 1240 and the second tapered waveguide 1221 have an overlapping portion. The first transition waveguide 1206 is used to receive the optical signal transmitted by the first coupling waveguide 1204 .

[0109] The second transition waveguide 1207 includes a fifth tapered waveguide 1250 and a sixth tapered waveguide 1251 connected to each other. The tip of the fifth tapered waveguide 1250 faces the fourth tapered waveguide 1241 . The fifth tapered waveguide 1250 and the fourth tapered waveguide 1241 have an overlapping portion. The second transition waveguide 1207 is used to receive the optical signal transmitted by the first transition waveguide 1206 .

[0110] The second coupling waveguide 1205 includes a seventh tapered waveguide 1230 and a straight waveguide 1231. The tip of the seventh tapered waveguide 1230 faces the sixth tapered waveguide 1251. The seventh tapered waveguide 1230 and the sixth tapered waveguide 1251 have an overlapping portion. The second coupling waveguide 1205 is used to receive the optical signal transmitted by the second transition waveguide 1207 and couple the optical signal to the optical chip 1100.

[0111] The end of the seventh tapered waveguide 1230 is connected to the straight waveguide 1231 , which is adjacent to the second end face 1209 . The optical field in the seventh tapered waveguide 1230 is coupled to the straight waveguide 1231 , and the straight waveguide 1231 couples the optical signal to the optical chip 1100 to achieve light reception.

[0112] In some embodiments, the first coupling waveguide 1204 may be a silicon nitride waveguide, and the second coupling waveguide 1205 may be a silicon waveguide. The refractive index of silicon nitride is around 2.0. Compared with silicon, the refractive index of silicon nitride is smaller, and the silicon nitride waveguide that can be manufactured is larger in size, thereby reducing the coupling loss between the first coupling waveguide 1204 and the single-mode optical fiber. In addition, silicon nitride has lower transmission loss. Using silicon nitride to prepare silicon nitride waveguides can reduce the transmission loss between the first coupling waveguide 1204 and the single-mode optical fiber.

[0113] Figure 8 for Figure 7 Middle AA section view, Fig. 9 for Figure 7 Middle BB section view, Fig.10 for Figure 7 Middle CC section view, Fig.11 for Figure 7 Middle DD section view, Fig.12 for Figure 7 EE section view. Figure 8-Figure 12 As shown, the thickness of the first coupling waveguide 1204 is smaller than the thickness of the second coupling waveguide 1205, and the cross-sectional dimensions of the first coupling waveguide 1204 and the second coupling waveguide 1205 may be different. When light is coupled between the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205, due to the difference in the cross-section of the optical waveguide, the transmission mode of the light will have a sudden change, thereby causing loss and polarization-related loss. Therefore, a special structure is designed at the coupling point of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 to reduce the loss and polarization-related loss.

[0114] The width of the second tapered waveguide 1221 of the first coupling waveguide 1204 and the width of the third tapered waveguide 1240 of the first transition waveguide 1206 are designed so that in the overlapped portion of the first coupling waveguide 1204 and the first transition waveguide 1206, the lateral width of the second tapered waveguide 1221 gradually narrows, while the lateral width of the third tapered waveguide 1240 gradually widens, thereby slowly releasing the light field transmitted in the first coupling waveguide 1204 into the first transition waveguide 1206, so that there is no mode mutation in the process of light coupling between the first coupling waveguide 1204 and the first transition waveguide 1206, and the mode conversion approximately satisfies the adiabatic condition, that is, both TE polarized light and TM polarized light can be well coupled to the first coupling waveguide 1204 or the first transition waveguide 1206, thereby reducing polarization-dependent loss and improving coupling efficiency.

[0115] The width of the fourth tapered waveguide 1241 of the first transition waveguide 1206 and the width of the fifth tapered waveguide 1250 of the second transition waveguide 1207 are designed so that in the overlapped portion of the first transition waveguide 1206 and the second transition waveguide 1207, the lateral width of the fourth tapered waveguide 1241 gradually narrows, and the lateral width of the fifth tapered waveguide 1250 gradually widens, thereby slowly releasing the light field transmitted in the first transition waveguide 1206 into the second transition waveguide 1207, so that there is no mode mutation in the process of light coupling between the first transition waveguide 1206 and the second transition waveguide 1207, and the mode conversion approximately satisfies the adiabatic condition, that is, both TE polarized light and TM polarized light can be well coupled to the first transition waveguide 1206 or the second transition waveguide 1207, thereby reducing polarization-related loss and improving coupling efficiency.

[0116] The width of the sixth tapered waveguide 1251 of the second transition waveguide 1207 and the width of the seventh tapered waveguide 1230 of the second coupling waveguide 1205 are designed so that in the overlapped portion of the second transition waveguide 1207 and the second coupling waveguide 1205, the lateral width of the sixth tapered waveguide 1251 gradually narrows, and the lateral width of the seventh tapered waveguide 1230 gradually widens, thereby slowly releasing the light field transmitted in the second transition waveguide 1207 into the second coupling waveguide 1205, so that there is no mode mutation in the process of light coupling between the second transition waveguide 1207 and the second coupling waveguide 1205, and the mode conversion approximately satisfies the adiabatic condition, that is, both TE polarized light and TM polarized light can be well coupled to the second transition waveguide 1207 or the second coupling waveguide 1205, thereby reducing polarization-dependent loss and improving coupling efficiency.

[0117] Since the refractive index of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 is greater than the refractive index of the second cladding 1203, and the refractive index of the second cladding 1203 is greater than the refractive index of the first cladding 1202, the light transmitted by the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205 is difficult to leak from the second cladding 1203 to the first cladding 1202, thereby reducing the leakage of the optical signal into the substrate 1201, thereby reducing the substrate leakage loss of the coupling waveguide, which is beneficial to improving the optical signal coupling efficiency from the optical fiber to the optical chip 1100.

[0118] In some embodiments, by adding a first cladding 1202 with a lower refractive index between the second cladding 1203 and the substrate 1201, better longitudinal constraints on the light field in the second cladding 1203 can be formed. In order to strengthen the horizontal constraints on the light field in the second cladding 1203, side grooves 1210 are set in the first cladding 1202 and the second cladding 1203. The side grooves 1210 are located on both sides of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205.

[0119] See also Figure 7 and Figure 8 Side grooves 1210 are provided on both sides of the first coupling waveguide 1204, the first transition waveguide 1206, the second transition waveguide 1207 and the second coupling waveguide 1205. The side grooves 1210 can be located in the first cladding 1202 and the second cladding 1203, and an opening is formed on the side of the side groove 1210 away from the substrate 1201, so that a U-shaped side groove 1210 is formed on the first cladding 1202 and the second cladding 1203.

[0120] In some embodiments, air grooves are etched on both sides of the first coupling waveguide 1204 and the second coupling waveguide 1205 in the second cladding 1203. During coupling packaging, glue is filled in the air grooves, and the refractive index of the glue is lower than that of the second cladding 1203. The side grooves 1210 are symmetrical with respect to the first coupling waveguide 1204 and the second coupling waveguide 1205, which also simulates the transverse refractive index distribution of the optical fiber to strengthen the constraint on the horizontal direction of the light field.

[0121] Along the width direction of the waveguide coupler 1200, the second cladding 1203 is divided into two separate parts by the side groove 1210, namely a central part 1260 and a peripheral part 1261, wherein the central part 1260 is located on the inner side and wrapped around the first coupling waveguide 1204 and the second coupling waveguide 1205; the peripheral part 1261 is arranged outside the central part 1260, and also plays a supporting and protective role.

[0122] By providing a side groove 1210 on the second cladding 1203, the mode field distribution jointly formed by the central portion 1260 and the first coupling waveguide 1204 can better match the mode field distribution of the optical fiber within the plane where the waveguide coupler 1200 contacts the optical fiber, thereby reducing the coupling loss at the first end face 1208 where the waveguide coupler 1200 contacts the optical fiber.

[0123] In some embodiments, within the first end face 1208 where the waveguide coupler 1200 contacts the optical fiber, the central portion 1260 and the first coupling waveguide 1204 together form a receiving mode field, and the optical fiber has a transmitting mode field. When the receiving mode field distribution and the transmitting mode field distribution match more closely, the optical signal loss is less. Therefore, the receiving mode field distribution can be changed by adjusting the size of the central portion 1260, that is, adjusting the width W1 of the side groove 1210, so as to better match the transmitting mode field distribution in the optical fiber, thereby reducing the optical signal loss.

[0124] In some embodiments, the width dimension W1 of the side trench 1210 is greater than 2 μm.

[0125] The side groove 1210 may adopt a groove structure established on the substrate 1201 , that is, the bottom surface of the side groove 1210 is located just on the surface of the substrate 1201 , so that part of the upper surface of the substrate 1201 can be exposed from the bottom surface of the side groove 1210 .

[0126] The bottom surface of the side groove 1210 may also be located in the first cladding layer 1202 , and the bottom surface of the side groove 1210 may also be located in the second cladding layer 1203 , that is, the bottom surface of the side groove 1210 may be at a certain distance from the surface of the substrate 1201 .

[0127] In some embodiments, the bottom surface of the side groove 1210 may also pass through the first cladding layer 1202 and enter the substrate 1201 , that is, the bottom surface of the side groove 1210 is located below the surface of the substrate 1201 .

[0128] In some embodiments, the side groove 1210 may be a polygonal groove, that is, the side groove 1210 may have a polygonal horizontal cross-section, such as a rectangular groove form, a trapezoidal groove form, etc.

[0129] In some embodiments, the medium filled in the side groove 1210 may be air, or may be filled with other dielectric materials having a refractive index lower than the refractive index of the second cladding layer 1203 .

[0130] In some embodiments, the formation of the side groove 1210 can be achieved directly by a one-step etching process. For example, a first cladding layer 1202 of silicon dioxide can be deposited on the substrate 1201, and a second cladding layer 1203 of silicon nitride can be deposited on the first cladding layer 1202. A first coupling waveguide 1204 and a second coupling waveguide 1205 are formed in the second cladding layer 1203. Then, the side groove 1210 is formed by etching downward on the surface of the second cladding layer 1203 on both sides of the first coupling waveguide 1204 and the second coupling waveguide 1205.

[0131] Side grooves 1210 are provided on both sides of the first coupling waveguide 1204 and the second coupling waveguide 1205, so that the light field of the second cladding 1203 can be confined to a range close to the mode field size of the single-mode optical fiber, thereby achieving optimal mode field matching with the standard single-mode optical fiber. Compared with the design without side grooves, the insertion loss can be effectively reduced.

[0132] In some embodiments, the transition waveguide between the first coupling waveguide 1204 and the second coupling waveguide 1205 may include not only the first transition waveguide 1206 and the second transition waveguide 1207 , and the number of the transition waveguides may be determined according to the position of the optical fiber.

[0133] Fig.13 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 2 .like Fig.13 As shown, the waveguide coupler 1200 also includes a first transition waveguide 1206, which is located in the second cladding 1203. Along the epitaxial growth direction, the first transition waveguide 1206 is located above the second coupling waveguide 1205, and the first coupling waveguide 1204 is located above the first transition waveguide 1206. One end of the first coupling waveguide 1204 is coupled and connected to the optical fiber, and the other end of the first coupling waveguide 1204 is coupled and connected to one end of the first transition waveguide 1206. The other end of the first transition waveguide 1206 is coupled and connected to one end of the second coupling waveguide 1205. The second coupling waveguide 1205 is optically connected to the optical chip 1100, so as to realize the coupling connection between the optical fiber and the optical chip 1100 through the first coupling waveguide 1204, the first transition waveguide 1206 and the second coupling waveguide 1205.

[0134] In some embodiments, there is a third height H3 between the first transition waveguide 1206 and the upper surface of the substrate 1201, there is a fourth height H4 between the first coupling waveguide 1204 and the upper surface of the substrate 1201, and the fourth height H4 is greater than the third height H3. The second coupling waveguide 1205 is adjacent to the first cladding 1202, there is a first gap G1 between the first coupling waveguide 1204 and the first transition waveguide 1206, there is a first overlapping portion between the first coupling waveguide 1204 and the first transition waveguide 1206, there is a second gap G2 between the first transition waveguide 1206 and the second coupling waveguide 1205, and there is a second overlapping portion between the second coupling waveguide 1205 and the first transition waveguide 1206.

[0135] Since the larger the gap between the waveguides, the greater the coupling difficulty, therefore, in order to reduce the coupling difficulty between the first transition waveguide 1206 and the second coupling waveguide 1205, the second gap G2 is smaller than the first gap G1, and the length of the second overlapping portion is smaller than the length of the first overlapping portion, so as to gradually transition the higher light field at the first end face 1208 to the first transition waveguide 1206 and finally reach the second coupling waveguide 1205, and in the process of light field transition, prevent the light field in the second cladding 1203 from leaking to the substrate 1201.

[0136] In some embodiments, the third height H3 has a size range of 2-4 μm, the fourth height H4 has a size range of 3-6 μm, the first gap G1 has a size range of 0.5-2 μm, and the second gap G2 has a size range of 0.1-0.8 μm.

[0137] In some embodiments, in order to improve the coupling efficiency between waveguides, the larger the gap between the waveguides, the longer the overlapping length between the waveguides. Thus, the size of the first gap G1 is 1.5 μm, and the length of the first overlapping part is 600 μm; the size of the second gap G2 is 0.78 μm, and the length of the second overlapping part is 300 μm.

[0138] In some embodiments, depending on the position of the optical fiber, no transition waveguide may be provided between the first coupling waveguide 1204 and the second coupling waveguide 1205 , that is, the waveguide coupler 1200 only includes the first coupling waveguide 1204 and the second coupling waveguide 1205 .

[0139] Fig.14 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 3 .like Fig.14As shown, along the epitaxial growth direction, the first coupling waveguide 1204 is located above the second coupling waveguide 1205, and the second coupling waveguide 1205 can be close to the first cladding 1202. The position of the first coupling waveguide 1204 in the second cladding 1203 corresponds to the transmitting optical fiber and the receiving optical fiber. For example, there is a third height H3 between the first coupling waveguide 1204 and the side of the substrate 1201 facing the first cladding 1202, and there is a first gap G1 between the first coupling waveguide 1204 and the second coupling waveguide 1205. When the first gap G1 is larger, it is more difficult for the first coupling waveguide 1204 and the second coupling waveguide 1205 to couple. Therefore, the first gap G1 needs to be located within a preset range to ensure the coupling efficiency between the first coupling waveguide 1204 and the second coupling waveguide 1205 and reduce the leakage of the light field in the second cladding 1203 to the substrate 1201.

[0140] In some embodiments, a third height H3 between the first coupling waveguide 1204 and the substrate 1201 has a size ranging from 2 to 4 μm, and a first gap G1 between the first coupling waveguide 1204 and the second coupling waveguide 1205 has a size ranging from 0.1 to 0.8 μm.

[0141] In some embodiments, the refractive index of the first coupling waveguide 1204 is greater than the refractive index of the second cladding 1203, the refractive index of the second coupling waveguide 1205 is greater than the refractive index of the second cladding 1203, and the first gap G1 between the first coupling waveguide 1204 and the second coupling waveguide 1205 is located within a preset range, so that the light transmitted by the first coupling waveguide 1204 can be gradually coupled from the first coupling waveguide 124 to the second coupling waveguide 1205, or the light transmitted by the second coupling waveguide 1205 can be gradually coupled from the second coupling waveguide 1205 to the first coupling waveguide 1204.

[0142] In this way, the signal light modulated by the optical chip 1100 is coupled to the second coupling waveguide 1205, the second coupling waveguide 1205 couples the signal light to the first coupling waveguide 1204, the first coupling waveguide 1204 couples the signal light to the transmitting optical fiber, and the signal light is transmitted to the optical fiber adapter 700 through the transmitting optical fiber, and then transmitted to the external optical fiber, thereby realizing the emission of light.

[0143] The received light transmitted by the external optical fiber is transmitted to the receiving optical fiber through the optical fiber adapter 700. The received light is coupled to the first coupling waveguide 1204 through the receiving optical fiber. The first coupling waveguide 1204 couples the received light to the second coupling waveguide 1205. The second coupling waveguide 1205 couples the received light to the optical chip 1100. The optical chip 1100 converts the received optical signal into an electrical signal, thereby realizing the reception of light.

[0144] In some embodiments, the refractive index of the first cladding 1202 may be a single refractive index, or the refractive index of the first cladding 1202 may be a gradient refractive index, that is, along the epitaxial growth direction, the refractive index of the first cladding 1202 gradually decreases, the refractive index of the first cladding 1202 near the lower surface is smaller than the refractive index of the substrate 1201, and the refractive index of the first cladding 1202 near the upper surface is smaller than the refractive index of the second cladding 1203, so as to prevent the light field in the second cladding 1203 from leaking to the substrate 1201.

[0145] Fig.15 A lateral cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure Figure 4 , Fig.16 FIG. 1 is a longitudinal cross-sectional view of an end face coupler in an optical module provided according to some embodiments of the present disclosure. Fig.15 and Fig.16 As shown, in some embodiments, the waveguide coupler 1200 may further include a third cladding 1211. Along the epitaxial growth direction, the first cladding 1202 is located on the substrate 1201, the second cladding 1203 is located on the first cladding 1202, and the third cladding 1211 is located on the second cladding 1203. The first cladding 1202 and the third cladding 1211 are symmetrical with respect to the second cladding 1203, and the refractive index of the third cladding 1211 is less than the refractive index of the second cladding 1203.

[0146] In some embodiments, the refractive index of the first cladding 1202 is the same as the refractive index of the third cladding 1211 to simulate the refractive index distribution of the optical fiber, which can form better confinement of the light field in the longitudinal direction.

[0147] In some embodiments, the refractive index of the first cladding 1202 is the same as the refractive index of the third cladding 1211, which means that the refractive indices are theoretically the same. As long as the error between the refractive index of the first cladding 1202 and the refractive index of the third cladding 1211 is within a preset error range, the refractive index of the first cladding 1202 can be considered to be the same as the refractive index of the third cladding 1211.

[0148] The function of the first cladding 1202 and the third cladding 1211 is to reflect the light leaked from the second cladding 1203 so that the light can only be transmitted within the second cladding 1203. They belong to the same concept and design. If there is a deviation between the refractive index of the first cladding 1202 and the refractive index of the third cladding 1211 due to differences in production and manufacturing or individual differences, the refractive index of the first cladding 1202 and the third cladding 1211 can also be considered to be the same.

[0149] The second cladding 1203 is provided with a first coupling waveguide 1204, a first transition waveguide 1206, a second transition waveguide 1207 and a second coupling waveguide 1205. One end of the first coupling waveguide 1204 is coupled and connected to the optical fiber, the other end of the first coupling waveguide 1204 is coupled and connected to one end of the first transition waveguide 1206, the other end of the first transition waveguide 1206 is coupled and connected to one end of the second transition waveguide 1207, the other end of the second transition waveguide 1207 is coupled and connected to one end of the second coupling waveguide 1205, and the other end of the second coupling waveguide 1205 is optically connected to the optical chip 1100, so as to realize optical coupling between the optical fiber and the optical chip 1100 through the waveguide coupler 1200.

[0150] Side grooves 1210 are etched on both sides of the waveguide in the second cladding 1203. The refractive index of the medium filled in the side grooves 1210 is smaller than the refractive index of the second cladding 1203 to simulate the transverse refractive index distribution of the optical fiber, thereby strengthening the horizontal constraint of the light field in the second cladding 1203 through the side grooves.

[0151] When light is transmitted in the first coupling waveguide 1204, the second transition waveguide 1207, the first transition waveguide 1206 and the second coupling waveguide 1205, since the refractive index of the second cladding 1203 is greater than the refractive index of the first cladding 1202 and the third cladding 1211, the light leaked to the second cladding 1203 will be reflected at the first cladding 1202 and the third cladding 1211. The reflected light can be coupled to the coupling waveguide or the transition waveguide and is difficult to leak to the substrate 1201, thereby reducing the substrate leakage loss and achieving the ultra-low coupling insertion loss of the standard single-mode optical fiber.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. An optical module, characterized in that: include: Circuit boards; An optical chip, electrically connected to the circuit board, and used for receiving an external optical signal; An optical fiber, used for transmitting the external optical signal; A waveguide coupler is coupled to the optical fiber, and is used to couple an external optical signal transmitted by the optical fiber to the optical chip; wherein the waveguide coupler includes: substrate; A first cladding layer is arranged on the substrate along the epitaxial growth direction; A second cladding layer is arranged on the first cladding layer along the epitaxial growth direction, the refractive index of the substrate is greater than the refractive index of the second cladding layer, and the refractive index of the second cladding layer is greater than the refractive index of the first cladding layer; a first coupling waveguide, located in the second cladding, one end of the first coupling waveguide being coupled to the optical fiber, and the first coupling waveguide being used to receive an external optical signal transmitted by the optical fiber; A second coupling waveguide, located in the second cladding, the second coupling waveguide being used to couple the external optical signal to the optical chip; at least one transition waveguide is located between the first coupling waveguide and the second coupling waveguide, a first gap is provided between the first coupling waveguide and the at least one transition waveguide, a first overlapping portion is provided between the first coupling waveguide and the at least one transition waveguide, a second gap is provided between the second coupling waveguide and the at least one transition waveguide, a second overlapping portion is provided between the second coupling waveguide and the at least one transition waveguide, the second gap is smaller than the first gap, a length of the second overlapping portion is smaller than a length of the first overlapping portion, and the at least one transition waveguide is used to couple an external optical signal transmitted by the first coupling waveguide to the second coupling waveguide.

2. The optical module according to claim 1, characterized in that: The waveguide coupler comprises a first transition waveguide, a first gap is formed between the first coupling waveguide and the first transition waveguide, a second gap is formed between the second coupling waveguide and the first transition waveguide, and the first gap is larger than the second gap; A first overlapping portion is provided between the first coupling waveguide and the first transition waveguide, and a second overlapping portion is provided between the second coupling waveguide and the first transition waveguide. The length of the first overlapping portion is greater than the length of the second overlapping portion.

3. The optical module according to claim 2, characterized in that: The size of the first gap is 1.5 μm, and the length of the first overlapped portion is 600 μm; The size of the second gap is 0.78 μm, and the length of the second overlapped portion is 300 μm.

4. The optical module according to claim 1, characterized in that: The waveguide coupler comprises a first transition waveguide and a second transition waveguide, wherein one end of the first transition waveguide is coupled to the first coupling waveguide, the other end of the first transition waveguide is coupled to one end of the second transition waveguide, and the other end of the second transition waveguide is coupled to the second coupling waveguide; There is a first gap between the first coupling waveguide and the first transition waveguide, there is a second gap between the second transition waveguide and the second coupling waveguide, there is a third gap between the first transition waveguide and the second transition waveguide, the second gap is smaller than the first gap, and the second gap is smaller than the third gap; There is a first overlapping portion between the first coupling waveguide and the first transition waveguide, there is a second overlapping portion between the second coupling waveguide and the second transition waveguide, there is a third overlapping portion between the first transition waveguide and the second transition waveguide, the length of the second overlapping portion is smaller than the length of the first overlapping portion, and the length of the second overlapping portion is smaller than the length of the third overlapping portion.

5. The optical module according to claim 4, characterized in that: The first gap is larger than the third gap, and the length of the first overlapping portion is larger than the length of the third overlapping portion; or, the first gap is smaller than the third gap, and the length of the first overlapping portion is smaller than the length of the third overlapping portion.

6. The optical module according to claim 4, characterized in that: The size of the first gap is in the range of 0.5 to 2 μm, the size of the second gap is in the range of 0.1 to 0.8 μm, and the size of the third gap is in the range of 0.5 to 2 μm.

7. The optical module according to claim 6, characterized in that: The size of the first gap is 1.3 μm, and the length of the first overlapping portion between the first coupling waveguide and the first transition waveguide is 400 μm; The size of the second gap is 0.43 μm, and the length of the second overlapping portion between the second coupling waveguide and the second transition waveguide is 100 μm; The size of the third gap is 0.85 μm, and the length of the third overlapping portion between the first transition waveguide and the second transition waveguide is 200 μm.

8. The optical module according to claim 1, characterized in that: The waveguide coupler further comprises: The third cladding is arranged on the second cladding along the epitaxial growth direction. The thickness of the third cladding is smaller than the thickness of the second cladding. The refractive index of the third cladding is the same as the refractive index of the first cladding.

9. An optical module, characterized in that: include: Circuit boards; An optical chip, electrically connected to the circuit board, and used for receiving an external optical signal; An optical fiber, used for transmitting the external optical signal; A waveguide coupler is coupled to the optical fiber, and the waveguide coupler is used to transmit an optical signal to the optical chip; wherein the waveguide coupler includes: substrate; A first cladding layer is disposed on the substrate; A second cladding layer is disposed on the first cladding layer, the refractive index of the substrate is greater than the refractive index of the second cladding layer, and the refractive index of the second cladding layer is greater than the refractive index of the first cladding layer; a first coupling waveguide, located in the second cladding, the first coupling waveguide comprising a first tapered waveguide and a second tapered waveguide connected to each other, the tip of the first tapered waveguide being coupled to the optical fiber, and the first coupling waveguide being used to receive an optical signal transmitted by the optical fiber; A second coupling waveguide is located in the second cladding, the second coupling waveguide includes a seventh tapered waveguide connected to a straight waveguide, the straight waveguide is adjacent to the optical chip, and the second coupling waveguide is used to couple the optical signal to the optical chip; at least one transition waveguide, located between the first coupling waveguide and the second coupling waveguide, a first overlapped portion between the tapered waveguide of the at least one transition waveguide facing the second tapered waveguide and the second tapered waveguide, a second overlapped portion between the tapered waveguide of the at least one transition waveguide facing the seventh tapered waveguide and the seventh tapered waveguide, a length of the second overlapped portion being shorter than a length of the first overlapped portion, and the at least one transition waveguide being used to couple an external optical signal transmitted by the first coupling waveguide to the second coupling waveguide; The side grooves are located in the first cladding layer and the second cladding layer, and the side grooves are located on both sides of the first coupling waveguide and the second coupling waveguide.

10. The optical module according to claim 9, characterized in that: The at least one transition waveguide comprises a first transition waveguide and a second transition waveguide, the first transition waveguide is located between the first coupling waveguide and the second coupling waveguide, and the second transition waveguide is located between the first transition waveguide and the second coupling waveguide; The first transition waveguide includes a third tapered waveguide and a fourth tapered waveguide connected to each other, and a first overlapping portion exists between the third tapered waveguide and the second tapered waveguide; The second transition waveguide includes a fifth tapered waveguide and a sixth tapered waveguide connected to each other, the fifth tapered waveguide and the fourth tapered waveguide have a third overlapping portion, the sixth tapered waveguide and the seventh tapered waveguide have a second overlapping portion, the length of the second overlapping portion is smaller than the length of the first overlapping portion, and the length of the second overlapping portion is smaller than the length of the third overlapping portion.

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