A laser chip and an optical module

Abstract

In the laser chip and optical module provided by the present application, the laser chip integrates a gain region, a grating region, and an electro-absorption modulation region. The gain region generates a light beam, and the grating region performs wavelength tuning on the light beam. The quantum well of the electro-absorption modulation region has a special structural design to ensure excellent transmission performance and further improve the signal modulation speed. At the same time, a silica layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the top layer of the quantum well and the metal electrode. The electro-absorption modulation region in the embodiment of the present application realizes a 25G signal modulation speed through special design, meeting the requirement of a 10-kilometer transmission distance. Therefore, the laser chip in the embodiment of the present application is a chip integrating the functions of gain, wavelength adjustment, and electrical signal modulation.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and in particular, to a laser chip and an optical module. Background Art

[0002] In today's optical fiber transmission systems, the requirements for light sources are getting higher and higher. High-speed, highly integrated, and wavelength-tunable light sources have always been a hot research topic in the industry. Among them, laser chips integrated with electro-absorption modulators have emerged. There are such technical problems in laser chips integrated with electro-absorption modulators: First, the signal modulation speed is basically at 10G and cannot reach the high signal modulation speed of 25G, and thus cannot meet the 10-kilometer transmission requirement; Second, the wavelength adjustment function cannot be integrated, resulting in the need to simultaneously enable and maintain light sources of a large number of different signals in a dense wavelength division multiplexing system. Summary of the Invention

[0003] Embodiments of this application provide a laser chip and an optical module. By integrating gain, wavelength tunability, and electrical signal modulation functions into one chip, a 25G signal modulation speed and a wavelength tuning range of more than 8 nm are achieved.

[0004] A laser chip provided by an embodiment of this application includes:

[0005] A gain region for generating a light beam;

[0006] A grating region for wavelength tuning of the light beam from the gain region;

[0007] An electro-absorption modulation region includes a quantum well. The quantum well includes a quantum well substrate layer, a first heterojunction layer, a potential well and a barrier layer, a second heterojunction layer, a backset layer, and a quantum well top layer that are stacked on each other. Among them, a silica layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the quantum well top layer and the metal electrode, for signal modulation of the light beam from the grating region.

[0008] The optical module provided by the embodiment of this application includes the above laser chip.

[0009] Beneficial effects: In the laser chip and optical module provided by this application, the laser chip integrates a gain region, a grating region, and an electro-absorption modulation region. The gain region generates photons and amplifies them. The grating region selects the frequency of the amplified light wave. The electro-absorption modulation region modulates a specific wavelength, and then realizes the output of a laser with a specific wavelength. The grating region can output light beams with different wavelengths. Moreover, the quantum well in the electro-absorption modulation region has a special structural design to ensure excellent transmission performance and further improve the signal modulation speed. At the same time, a silicon dioxide layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the top layer of the quantum well and the metal electrode. The setting of the silicon dioxide layer can adjust the chip capacitance to obtain a smaller parasitic capacitance and further improve the signal modulation speed. The electro-absorption modulation region in the embodiment of this application realizes a 25G signal modulation speed through special design, meeting the requirements of a 10-kilometer transmission distance. Therefore, the laser chip in the embodiment of this application is a chip integrating gain, wavelength adjustability, and electro-signal modulation functions, which is of great significance to the optical fiber transmission system. Brief Description of the Drawings

[0010] In order to more clearly illustrate the technical solutions in this disclosure, the following will briefly introduce the drawings required for use in some embodiments of this disclosure. Obviously, the drawings in the following description are only the drawings of some embodiments of this disclosure. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings. In addition, the drawings in the following description can be regarded as schematic diagrams, and are not limitations on the actual size of the products, the actual processes of the methods, the actual timings of the signals, etc. involved in the embodiments of this disclosure.

[0011] Figure 1 It is a connection relationship diagram of an optical communication system according to some embodiments;

[0012] Figure 2 It is a structural diagram of an optical network terminal according to some embodiments;

[0013] Figure 3 It is a structural diagram of an optical module according to some embodiments;

[0014] Figure 4 It is an exploded view of an optical module according to some embodiments;

[0015] Figure 5 It is a schematic external view of a laser chip according to some embodiments;

[0016] Figure 6 It is a schematic diagram of the outer edge growth structure of a laser chip according to some embodiments;

[0017] Figure 7 It is a schematic diagram of the quantum well structure of the electro-absorption modulation region in a laser chip according to some embodiments;

[0018] Figure 8 Schematic diagram of the modulation speed of a laser chip according to some embodiments;

[0019] Figure 9 Schematic diagram of the change of the wavelength of a laser chip with the injection current according to some embodiments;

[0020] Figure 10 Schematic diagram of the manufacturing process of a laser chip according to some embodiments. Detailed implementation manners

[0021] The technical solutions in some embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided by the present disclosure fall within the scope of protection of the present disclosure.

[0022] Unless otherwise required by the context, throughout the specification and claims, the term "comprise" and its other forms such as the third-person singular form "comprises" and the present participle form "comprising" are interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples", etc. are intended to indicate that the specific features, structures, materials or characteristics related to the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0023] Hereinafter, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present disclosure, unless otherwise specified, the meaning of "a plurality" is two or more.

[0024] In describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. For example, in describing some embodiments, the term "connected" may be used to indicate that two or more components have direct physical or electrical contact with each other. Another example is that in describing some embodiments, the term "coupled" may be used to indicate that two or more components have direct physical or electrical contact. However, the term "coupled" or "communicatively coupled" may also mean that two or more components do not have direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the content herein.

[0025] "At least one of A, B, and C" has the same meaning as "at least one of A, B, or C", and both include the following combinations of A, B, and C: only A, only B, only C, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0026] "A and / or B" includes the following three combinations: only A, only B, and the combination of A and B.

[0027] The use of "suitable for" or "configured to" herein means open and inclusive language, which does not exclude devices that are suitable for or configured to perform additional tasks or steps.

[0028] As used herein, "about", "substantially", or "approximately" includes the stated value and the average value within an acceptable deviation range of the specific value, where the acceptable deviation range is determined by a person of ordinary skill in the art considering the measurement being discussed and the error associated with the measurement of the specific quantity (i.e., the limitations of the measurement system).

[0029] In optical communication technology, light is used to carry the information to be transmitted, and the optical signal carrying the information is transmitted through an information transmission device such as an optical fiber or an optical waveguide to an information processing device such as a computer to complete the transmission of the information. Since the optical signal has a passive transmission characteristic when transmitted through an optical fiber or an optical waveguide, low-cost and low-loss information transmission can be achieved. In addition, the signal transmitted by an information transmission device such as an optical fiber or an optical waveguide is an optical signal, while the signal that an information processing device such as a computer can recognize and process is an electrical signal. Therefore, in order to establish an information connection between an information transmission device such as an optical fiber or an optical waveguide and an information processing device such as a computer, it is necessary to realize the mutual conversion between the electrical signal and the optical signal.

[0030] The optical module realizes the above-mentioned function of mutual conversion between optical signals and electrical signals in the field of optical fiber communication technology. The optical module includes an optical port and an electrical port. The optical module realizes optical communication with information transmission devices such as optical fibers or optical waveguides through the optical port, and realizes electrical connection with an optical network terminal (for example, an optical modem) through the electrical port. The electrical connection is mainly used for power supply, I2C signal transmission, data signal transmission, grounding, etc.; the optical network terminal transmits the electrical signal to an information processing device such as a computer through a network cable or Wi-Fi (Wireless Fidelity).

[0031] Figure 1 It is a connection diagram of an optical communication system according to some embodiments. As Figure 1 shown, the optical communication system mainly includes a remote server 1000, a local information processing device 2000, an optical network terminal 100, an optical module 200, an optical fiber 101, and a network cable 103.

[0032] One end of the optical fiber 101 is connected to the remote server 1000, and the other end is connected to the optical network terminal 100 through the optical module 200. The optical fiber itself can support long-distance signal transmission, such as signal transmission of several kilometers (6 kilometers to 8 kilometers). On this basis, if a repeater is used, theoretically ultra-long-distance transmission can be achieved. Therefore, in a general optical communication system, the distance between the remote server 1000 and the optical network terminal 100 can usually reach several kilometers, dozens of kilometers, or hundreds of kilometers.

[0033] One end of the network cable 103 is connected to the local information processing device 2000, and the other end is connected to the optical network terminal 100. The local information processing device 2000 can be any one or several of the following devices: router, switch, computer, mobile phone, tablet computer, television, etc.

[0034] The physical distance between the remote server 1000 and the optical network terminal 100 is greater than the physical distance between the local information processing device 2000 and the optical network terminal 100. The connection between the local information processing device 2000 and the remote server 1000 is completed by the optical fiber 101 and the network cable 103; while the connection between the optical fiber 101 and the network cable 103 is completed by the optical module 200 and the optical network terminal 100.

[0035] The optical module 200 includes an optical port and an electrical port. The optical port is configured to be connected to the optical fiber 101, so that the optical module 200 establishes a bidirectional optical signal connection with the optical fiber 101; the electrical port is configured to be connected to the optical network terminal 100, so that the optical module 200 establishes a bidirectional electrical signal connection with the optical network terminal 100. The optical module 200 realizes the mutual conversion between optical signals and electrical signals, so that a connection is established between the optical fiber 101 and the optical network terminal 100. For example, the optical signal from the optical fiber 101 is converted into an electrical signal by the optical module 200 and then input into the optical network terminal 100, and the electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module 200 and input into the optical fiber 101.

[0036] The optical network terminal 100 includes a housing that is roughly rectangular, and an optical module interface 102 and a network cable interface 104 arranged on the housing. The optical module interface 102 is configured to access the optical module 200, so that the optical network terminal 100 establishes a bidirectional electrical signal connection with the optical module 200; the network cable interface 104 is configured to access the network cable 103, so that the optical network terminal 100 establishes a bidirectional electrical signal connection with the network cable 103. The optical module 200 and the network cable 103 are connected through the optical network terminal 100. For example, the optical network terminal 100 transmits the electrical signal from the optical module 200 to the network cable 103, and transmits the signal from the network cable 103 to the optical module 200. Therefore, the optical network terminal 100, as the host computer of the optical module 200, can monitor the operation of the optical module 200. In addition to the optical network terminal 100, the host computer of the optical module 200 can also include an optical line terminal (Optical Line Terminal, OLT) and the like.

[0037] The remote server 1000 establishes a bidirectional signal transmission channel with the local information processing device 2000 through the optical fiber 101 , the optical module 200 , the optical network terminal 100 and the network cable 103 .

[0038] Figure 2 FIG. 1 is a structural diagram of an optical network terminal according to some embodiments. In order to clearly show the connection relationship between the optical module 200 and the optical network terminal 100, Figure 2 Only the structure of the optical network terminal 100 related to the optical module 200 is shown. Figure 2 As shown, the optical network terminal 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, 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 protrusions such as fins that increase the heat dissipation area.

[0039] The optical module 200 is inserted into the cage 106 of the optical network terminal 100. The cage 106 fixes the optical module 200, and the heat generated by the optical module 200 is conducted 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, thereby establishing a two-way electrical signal connection between the optical module 200 and the optical network terminal 100. In addition, the optical port of the optical module 200 is connected to the optical fiber 101, thereby establishing a two-way electrical signal connection between the optical module 200 and the optical fiber 101.

[0040] Figure 3 It is a structural diagram of an optical module according to some embodiments. Figure 4 It is an exploded view of an optical module according to some embodiments. As Figure 3 and Figure 4 shown, the optical module 200 includes a housing, a circuit board 105 disposed in the housing, and an optical transceiver device.

[0041] The housing includes an upper housing 201 and a lower housing 202. The upper housing 201 covers the lower housing 202 to form the above-mentioned housing with two openings 204 and 205; the outer contour of the housing generally presents a rectangular body.

[0042] In some embodiments of the present disclosure, the lower housing 202 includes a bottom plate and two lower side plates located on both sides of the bottom plate and perpendicular to the bottom plate; the upper housing 201 includes a cover plate and two upper side plates located on both sides of the cover plate and perpendicular to the cover plate. The two side walls are combined with the two side plates to realize the upper housing 201 covering the lower housing 202.

[0043] The direction where the line connecting the two openings 204 and 205 is located may be consistent with the length direction of the optical module 200 or may not be consistent with the length direction of the optical module 200. Exemplarily, the opening 204 is located at the end of the optical module 200 ( Figure 3 the left end), and the opening 205 is also located at the end of the optical module 200 ( Figure 3 the right end). Or, the opening 204 is located at the end of the optical module 200, while the opening 205 is located at the side of the optical module 200. Among them, the opening 204 is an electrical port, and the gold fingers of the circuit board 105 extend out from the opening 204 and are inserted into the upper computer (such as the optical network terminal 100); the opening 205 is an optical port configured to access the external optical fiber 101 so that the optical fiber 101 is connected to the optical transceiver device inside the optical module 200.

[0044] Adopting the assembly method of combining the upper housing 201 and the lower housing 202 facilitates the installation of components such as the circuit board 105 and the optical transceiver device into the housing, and the upper housing 201 and the lower housing 202 can form a package protection for these components. In addition, when assembling components such as the circuit board 105, it is convenient for the deployment of the positioning components, heat dissipation components, and electromagnetic shielding components of these components, which is beneficial to the implementation of automated production.

[0045] In some embodiments, the upper housing 201 and the lower housing 202 are generally made of metal materials, which is beneficial to achieving electromagnetic shielding and heat dissipation.

[0046] In some embodiments, the optical module 200 further includes an unlocking component 203 located on the outer wall of its housing. The unlocking component 203 is configured to achieve a fixed connection between the optical module 200 and the host computer, or to release the fixed connection between the optical module 200 and the host computer.

[0047] Exemplarily, the unlocking component 203 is located on the outer walls of the two lower side plates of the lower housing 202 and includes a latching component that matches the cage of the host computer (for example, the cage 106 of the optical network terminal 100). When the optical module 200 is inserted into the cage of the host computer, the latching component of the unlocking component 203 fixes the optical module 200 in the cage of the host computer; when the unlocking component 203 is pulled, the latching component of the unlocking component 203 moves accordingly, thereby changing the connection relationship between the latching component and the host computer to release the latching relationship between the optical module 200 and the host computer, so that the optical module 200 can be pulled out from the cage of the host computer.

[0048] The circuit board 105 includes circuit traces, electronic components, and chips. The electronic components and chips are connected together according to the circuit design through the circuit traces to achieve functions such as power supply, electrical signal transmission, and grounding. The electronic components may include, for example, capacitors, resistors, triodes, and metal-oxide-semiconductor field-effect transistors (MOSFETs). The chips may include, for example, a microcontroller unit (MCU), a limiting amplifier, a clock and data recovery chip (CDR), a power management chip, and a digital signal processing (DSP) chip.

[0049] The circuit board 105 is generally a rigid circuit board. Due to its relatively hard material, the rigid circuit board can also achieve a bearing function. For example, the rigid circuit board can stably bear the chips; the rigid circuit board can also be inserted into the electrical connectors in the cage of the host computer.

[0050] The circuit board 105 further includes a gold finger formed on its end surface, and the gold finger is composed of a plurality of independent pins. The circuit board 105 is inserted into the cage 106, and is electrically connected to the electrical connector in the cage 106 through the gold finger. The gold finger can be provided only on the surface of one side of the circuit board 105 (such as Figure 4 the upper surface shown), or can be provided on the upper and lower surfaces of the circuit board 105 to adapt to the occasion with a large demand for the number of pins. The gold finger is configured to establish an electrical connection with the host computer to achieve power supply, grounding, 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 cooperation with rigid circuit boards as a supplement to the rigid circuit boards.

[0051] The optical module with a silicon photonics structure further includes a silicon photonics chip 400. The silicon photonics chip 400 itself does not have a light source, and the light source component 500 is used as an external light source for the silicon photonics chip 400. The light source component 500 can be a laser box. A laser chip is encapsulated inside the laser box, and the laser chip emits light to generate a laser beam. The light source component 500 is used to provide the emitted laser to the silicon photonics chip 400. The laser becomes the preferred light source for the optical module and even optical fiber transmission with better single-wavelength characteristics and better wavelength tuning characteristics. For other types of light such as LED light, etc., common optical communication systems generally do not adopt it. Even if this kind of light source is adopted in a special optical communication system, the characteristics of its light source and chip components are quite different from those of the laser, making the optical module using the laser and the optical module using other light sources have great technical differences. Those skilled in the art generally do not think that these two types of optical modules can give each other technical inspiration.

[0052] The bottom surface of the silicon photonics chip 400 and the bottom surface of the light source component 500 are respectively arranged on the substrate. There is an optical connection between the silicon photonics chip and the light source. The optical path is very sensitive to the positional relationship between the silicon photonics chip and the light source. Materials with different coefficients of thermal expansion will cause different degrees of deformation, which is not conducive to the realization of the preset optical path; in the embodiment of the present application, the silicon photonics chip and the light source are arranged on the same substrate. The substrate of the same material deforms, which will equally affect the positions of the silicon photonics chip and the light source, avoiding a large change in the relative position between the silicon photonics chip and the light source; it is preferred that the coefficient of thermal expansion of the substrate material is close to the coefficient of thermal expansion of the silicon photonics chip and / or the light source material. The main material of the silicon photonics chip is silicon, the light source can use kovar metal, and the substrate generally selects silicon or glass, etc.

[0053] There are many relationships between the substrate and the circuit board 105. One of the ways is as Figure 4As shown, the circuit board 105 has openings penetrating through the upper and lower surfaces, and the silicon photonic chip and / or the light source are disposed in the openings. In this way, the silicon photonic chip and / or the light source can dissipate heat to both the upper surface and the lower surface of the circuit board simultaneously. The substrate is disposed on one side of the circuit board. The silicon photonic chip and / or the light source pass through the opening of the circuit board and are then placed on the heat dissipation substrate, and the substrate plays a role of supporting and heat dissipation. In another way, the circuit board is not provided with an opening, and the substrate is disposed on the circuit board. Specifically, the substrate can be disposed on the surface of the circuit board or embedded in the circuit board, and the silicon photonic chip and the light source are disposed on the surface of the substrate.

[0054] The bottom surface of the light source assembly 500 is disposed on the substrate. The light source assembly 500 emits light from the side, and the emitted light enters the silicon photonic chip 400. The silicon photonic chip uses silicon as the main base material, and silicon is not an ideal light-emitting material. A light source cannot be integrated in the silicon photonic chip 400, and an external light source assembly 500 is required to provide the light source. The light provided by the light source assembly 500 to the silicon photonic chip is an emission light with a single wavelength and stable power, and does not carry any data. The silicon photonic chip 400 modulates the emission light to load the data onto the emission light.

[0055] The bottom surface of the silicon photonic chip 400 is disposed on the substrate, and the side surface of the silicon photonic chip 400 receives the emission light from the light source; the modulation of the emission light and the demodulation of the received light are completed by the silicon photonic chip. The surface of the silicon photonic chip is provided with pads electrically connected to the circuit board by wire bonding. Specifically, the circuit board provides a data signal from the host computer to the silicon photonic chip, and the silicon photonic chip modulates the data signal onto the emission light. After the received light from the outside is demodulated into an electrical signal by the silicon photonic chip, it is output to the host computer through the circuit board.

[0056] Both the first optical fiber ribbon 600 and the second optical fiber ribbon 700 are formed by combining multiple optical fibers; in the embodiment of the present application, the first optical fiber ribbon 600 is an emission optical fiber ribbon, and the second optical fiber ribbon 700 is a reception optical fiber ribbon; one end of the first optical fiber ribbon 600 is connected to the silicon photonic chip 400, and the other end is connected to the optical fiber interface 800; one end of the second optical fiber ribbon 700 is connected to the silicon photonic chip 400, and the other end is connected to the optical fiber interface 800; the optical fiber interface 800 is connected to an external optical fiber. It can be seen that the optical connection between the silicon photonic chip 400 and the optical fiber interface 800 is realized through the first optical fiber ribbon 600 and the second optical fiber ribbon 700, and the optical fiber interface 800 realizes the optical connection with the external optical fiber of the optical module.

[0057] The light source component 500 transmits the emission light without carrying signals into the silicon photonic chip 400. The silicon photonic chip 400 modulates the emission light without carrying signals. Specifically, data is loaded into the emission light without carrying signals, and then the emission light without carrying signals is modulated into the emission light carrying data signals. The emission light carrying data signals is transmitted to the fiber optic interface 800 through the first fiber optic ribbon 600 and then transmitted to the external optical fiber through the fiber optic interface 800, thereby transmitting the light carrying data signals to the external optical fiber of the optical module and realizing the conversion of electrical signals into optical signals.

[0058] The optical signal from the external optical fiber is transmitted to the fiber optic interface 800, and then the optical signal is transmitted to the silicon photonic chip 400 through the second fiber optic ribbon 700. The silicon photonic chip 400 demodulates the optical signal into an electrical signal and outputs it to the host computer through the circuit board, realizing the conversion of optical signals into electrical signals.

[0059] The light source component 500 in the embodiment of the present application includes a laser chip. On the surface of the laser chip in the embodiment of the present application, a gain region, a grating region, and an electro-absorption modulation region are integrated. The gain region generates photons and is amplified. The grating region selects the frequency of the amplified light wave. The electro-absorption modulation region modulates a specific wavelength, and then realizes the output of a laser with a specific wavelength; by changing the magnitude of the current injected into the grating region, the refractive index of the waveguide in the grating region can be continuously changed, thereby outputting light beams with different wavelengths; the length of the electro-absorption modulation region is designed to be relatively long. Only a long enough electro-absorption modulation region can ensure sufficient electro-absorption ability, ensure that the reaction speed of the device is fast enough, improve the signal modulation speed, and the quantum well in the electro-absorption modulation region has a special structural design to ensure excellent transmission performance and further improve the signal modulation speed; at the same time, a silicon dioxide layer is filled between the quantum well substrate layer and the metal electrode, between the back layer and the metal electrode, and between the top layer of the quantum well and the metal electrode. The setting of the silicon dioxide layer can adjust the chip capacitance to obtain a small parasitic capacitance and further improve the signal modulation speed; the electro-absorption modulation region in the embodiment of the present application realizes a 25G signal modulation speed through special design, meeting the requirements of a 10-kilometer transmission distance. Therefore, the laser chip in the embodiment of the present application is a chip integrating gain, wavelength adjustable, and electrical signal modulation functions, which has important significance for the optical fiber transmission system.

[0060] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0061] Figure 5 It is a schematic diagram of the appearance of a laser chip according to some embodiments; Figure 6 It is a schematic diagram of the outer edge growth structure of a laser chip according to some embodiments.

[0062] As Figure 5As shown, in the embodiment of the present application, the surface of the laser chip includes a gain region, a grating region, and an electro-absorption modulation region. The gain region and the electro-absorption modulation region are respectively located at two end sides, and the grating region is located between the gain region and the electro-absorption modulation region. The gain region generates photons and amplifies them. The grating region selects the frequency of the amplified light wave. The electro-absorption modulation region modulates a specific wavelength, and then realizes the output of a laser with a specific wavelength. The electro-absorption modulation region can change the magnitude of the light absorption loss of itself, and thus realizes the modulation of the optical signal. The electro-absorption modulation region includes a quantum well structure, which is formed by stacking layers of materials with different bandgaps one on top of the other.

[0063] A first isolation region is provided between the gain region and the grating region, and a second isolation region is provided between the grating region and the electro-absorption modulation region. As Figure 5 shown, the length of the gain region is 375 μm, the length of the grating region is 150 μm, the length of the electro-absorption modulation region is 110 μm, the length of the first isolation region is 45 μm, and the length of the second isolation region is 80 μm.

[0064] As Figure 6 shown, the gain region includes an InP cushion layer, a waveguide layer, a gain quantum well structure layer, and a p-type doped InP layer stacked from bottom to top, corresponding to Figure 6 the n-InP substate, buffer layers layer, waveguide layer, Gain MQW / SCH layers layer, and P-InP clad layer in the left gain region respectively.

[0065] The grating region includes an InP cushion layer, a grating layer, and a waveguide layer stacked from bottom to top, corresponding to Figure 6 the n-InP substate, buffer layers layer, Grating layer layer, and waveguide layer in the middle grating region respectively.

[0066] The electro-absorption modulation region includes an InP cushion layer and an electro-absorption modulation quantum well structure layer stacked from bottom to top, corresponding to Figure 6 the n-InP substate, buffer layers layer and Gain MQW / SCHlayers layer in the right electro-absorption modulation region respectively.

[0067] In the embodiments of the present application, for the convenience of description, the first layer, the second layer, etc. are defined in the direction from top to bottom. The first layer, the second layer, the third layer, and the fourth layer of the gain region are a p-type doped InP layer, a gain quantum well structure layer, a waveguide layer, and an InP buffer layer respectively; the first layer and the second layer of the grating region are empty, the third layer is the waveguide layer, the fourth layer is the grating layer, and the fifth layer is the InP buffer layer; the first layer and the second layer of the electro-absorption modulation region are empty, the third layer and the fourth layer are electro-absorption modulation quantum well structure layers, and the fifth layer is the InP buffer layer. It can be seen that the first layer and the second layer corresponding to the grating region and the electro-absorption modulation region are blank, that is, the first layer and the second layer of the gain region are blank in the right direction. Figure 6 In the gain region is located on the left side, and the electro-absorption modulation region is located on the right side. Thus, it can be seen that in the embodiments of the present application, an innovative lateral coupling process is adopted between the gain region and the grating region, rather than the traditional end-to-end growth process, thereby reducing the need for one epitaxial growth.

[0068] The light generated from the quantum wells in the gain region will finally flow laterally into the waveguide layer and perform wavelength selection in the grating region.

[0069] The embodiments of the present application provide a lateral coupling technology, which reduces the loss from the gain region to the wavelength adjustment region and simplifies the process flow at the same time.

[0070] In the embodiments of the present application, the grating region includes a grating layer and a waveguide layer. The grating layer (labeled grating material in the figure) is an InGaAsP material with a photoluminescence peak of 1250 nm and a thickness of 300 Å; the waveguide layer is an InGaAsP material with a photoluminescence peak of 1380 nm and a thickness of 2900 Å, and the waveguide layer is lightly doped with 2×10¹⁷ / cubic centimeter. In the embodiments of the present application, the setting of the material thickness needs to meet the requirements of the wavelength modulation range and have low optical propagation loss.

[0071] By changing the magnitude of the current injected into the grating region to output light beams of different wavelengths, in the embodiments of the present application, the grating is a distributed Bragg reflector grating, and the entire light source chip only undergoes one holographic exposure to form the grating, so the period of the grating is fixed; by changing the magnitude of the current injected into the grating region, the refractive index of the waveguide in the grating region can be continuously changed, thereby realizing the continuous change of the grating passband and selecting the Fabry-Perot mode corresponding to the target wavelength.

[0072] Compared with mechanical tuning and thermal tuning for wavelength adjustment, electrical tuning for wavelength adjustment has a larger wavelength adjustment range, a faster wavelength switching speed, and can better meet the requirements of fiber optic communication for lasers. Electrical tuning is achieved by injecting carriers into the grating region to change the refractive index of its material.

[0073] Figure 9 Schematic diagram of the change of the wavelength of a laser chip with the injected current according to some embodiments; as Figure 9As shown, when the injection current of the laser chip in the embodiment of the present application is 50 mA, the wavelength change is about 11 nm, which can cover the wavelength change requirement of 8 nm with a margin.

[0074] In summary, in the laser chip of the embodiment of the present application, by changing the current magnitude in the injection grating region, the refractive index of the waveguide in the grating region can be continuously changed, thereby outputting light beams of different wavelengths.

[0075] In the embodiment of the present application, in order to enable the laser chip to achieve an electro-modulation rate of 25 GHz and meet the requirement of a transmission distance of 10 km, the following special structure is provided for the electro-absorption modulation region in the embodiment of the present application:

[0076] In some embodiments, the material of the electron trap structure in the electro-absorption modulation region is determined by the position of the overall photoluminescence peak in the electro-absorption region. After repeated experiments, its value is the target wavelength minus 60 nm. Only near this design value can the transmission performance be optimized. Figure 7 Schematic diagram of the quantum well structure in the electro-absorption modulation region of the laser chip according to some embodiments; as Figure 7 shown, the quantum well includes a relatively stacked quantum well substrate layer, a first heterojunction layer, a potential well and a barrier layer, a second heterojunction layer, a backset layer, and a quantum well top layer. Among them, a silicon dioxide layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the quantum well top layer and the metal electrode. The parameters of each layer are as follows:

[0077] Among them, the quantum well substrate layer is an n-type InP substrate; above it is the first heterojunction layer, made of InGaAsP material with a photoluminescence peak of 1170 nm, and the thickness is 420 Å (1 Å is 10^(-10) meters); above it are 8 groups of potential wells and 8 groups of barriers. Among them, the thickness of the 8 groups of potential wells is 90 Å, and a 0.7% compression is required in the potential well region in the design; the thickness of the 8 groups of barriers is 50 Å, and the material is InGaAsP material with a photoluminescence peak of 1170 nm, and a 0.3% relaxation is required in the barrier region in the design; above it is the second heterojunction layer, whose parameters are the same as those of the first heterojunction layer; above it is an 800 Å InP backset layer used to dilute the doping flowing in from the upper layer; the topmost is p-type InP material.

[0078] In some embodiments, the length of the electro-absorption modulation region is 110 μm. A long enough electro-absorption modulation region length can ensure sufficient electro-absorption ability, so that the extinction ratio of the device meets the application requirements; a long enough electro-absorption modulation region length can have a smaller capacitance and smaller time parameters, thereby improving the device response speed.

[0079] In some embodiments, a silica layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the top quantum well layer and the metal electrode; the materials of the quantum well substrate layer, the backset layer, and the top quantum well layer are all InP materials. A thicker silica material is filled between the InP material of the chip and the metal electrode to adjust the chip capacitance; in the embodiments of the present application, the silica layer uses silica with a thickness of 5000 Å to obtain a smaller parasitic capacitance and improve the device speed. Figure 8 Schematic diagram of the modulation speed of a laser chip according to some embodiments; as Figure 8 shown, the 3dB bandwidth of S21 exceeds 17 GHz, and this value can meet 25G modulation and transmission applications.

[0080] In summary, in the laser chip in the embodiments of the present application, the length of the electro-absorption modulation region is designed to be relatively long. Only a long enough electro-absorption modulation region can ensure sufficient electro-absorption ability, ensure that the device reaction speed is fast enough, improve the signal modulation speed, and the quantum wells in the electro-absorption modulation region have a special structural design to ensure excellent transmission performance and further improve the signal modulation speed; at the same time, a silica layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the top quantum well layer and the metal electrode. The setting of the silica layer can adjust the chip capacitance, obtain a smaller parasitic capacitance, and further improve the signal modulation speed; the electro-absorption modulation region in the embodiments of the present application realizes a 25G signal modulation speed through special design and meets the requirements of a 10-kilometer transmission distance.

[0081] In the embodiments of the present application, integrating the three functions of gain, wavelength adjustment, and electrical signal modulation onto one laser chip and being suitable for large-scale manufacturing to form a simple and reliable process flow has become the most important and bottleneck problem. For this reason, the embodiments of the present application provide a preparation process for a laser chip.

[0082] In the embodiments of the present application, an innovative lateral coupling process is adopted for the gain region and the grating region instead of the traditional end-to-end growth process, thereby reducing the need for one epitaxial growth. Figure 10 Schematic diagram of the manufacturing process of a laser chip according to some embodiments, as Figure 10 shown, the specific method is as follows:

[0083] One: Figure 10 (1) shows the substrate wafer, which only has a grating waveguide layer. A grating is formed by holographic exposure, and the non-grating area is etched to form Figure 10 (2) morphology.

[0084] Second: Perform epitaxial growth. Sequentially grow an InP material buffer layer, a waveguide layer (the material is InGaAsP with a photoluminescence peak of 1380 nm, 2900 Å), an InP material stop layer, and the quantum well structure of the gain region. Then, grow a p-type doped InP material, and finally, grow an InGaAsP material with a photoluminescence peak of 1250 to form as Figure 10 (3) Morphology.

[0085] Third: Grow a thin layer of silicon dioxide on the wafer. Through dry etching, remove the silicon dioxide layer in the grating region and the electro-absorption region. Through selective wet etching, remove the InGaAsP material with a photoluminescence peak of 1250 and the p-type doped InP material in the grating region and the electro-absorption region. After removing all the silicon dioxide, form Figure 10 (4).

[0086] Fourth: Through selective wet etching, only etch the InGaAsP material without etching the InP material, and the InGaAsP material with a photoluminescence peak of 1250 in the gain region and the gain quantum well structure in the grating region and the electro-absorption region can be removed, thereby forming Figure 10 (5) Shape. At this time, the light generated from the quantum wells in the gain region will finally flow laterally into the waveguide layer and perform wavelength selection in the grating region. Finally, perform traditional tail-connection process etching and growth in the grating region and the electro-absorption region to form Figure 10 (6) Shape.

[0087] This design provides a verified process flow: By adopting the lateral coupling technology, the loss from the gain region to the wavelength adjustment region is reduced, and at the same time, the process flow is simplified, the number of epitaxial growth times is reduced, which is suitable for mass production.

[0088] In the laser chip and optical module provided by this application, the laser chip integrates a gain region, a grating region, and an electro-absorption modulation region. By changing the magnitude of the current injected into the grating region, the refractive index of the waveguide in the grating region can be continuously changed, thereby outputting light beams of different wavelengths; the quantum wells in the electro-absorption modulation region have a special structural design to ensure excellent transmission performance and further improve the signal modulation speed; at the same time, silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the quantum well top layer and the metal electrode; the electro-absorption modulation region in the embodiments of this application can achieve a 25G signal modulation speed through special design, meeting the requirements of a 10-kilometer transmission distance. Therefore, the laser chip in the embodiments of this application is a chip integrating gain, wavelength adjustable, and electrical signal modulation functions.

[0089] The laser chip provided by the embodiments of the present application can, on the one hand, achieve a 25G signal modulation speed and meet the requirements of high-speed optical fiber communication networks for 25G light sources; on the other hand, it can achieve a wavelength adjustment range of more than 8nm, and the technology can be transplanted to various wavelengths, not limited to dense wavelength division multiplexing applications; on the third hand, in the face of complex functional integration requirements, the embodiments of the present application provide a proven process flow: using lateral coupling technology, reducing the loss from the gain region to the wavelength adjustment region, while simplifying the process flow, reducing the number of epitaxial growths, and being suitable for mass production.

[0090] As described above, the above is only a specific implementation manner of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present disclosure, thinking of changes or substitutions, should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A laser chip, characterized in that, Comprising: A gain region for generating a light beam; the gain region includes an InP buffer layer, a waveguide layer, a gain quantum well structure layer, and a p-type doped InP layer arranged from bottom to top; A grating region for wavelength tuning of the light beam from the gain region; the grating region includes an InP buffer layer, a grating layer, and a waveguide layer arranged from bottom to top; the waveguide layer of the grating region is the top layer of the grating region; An electro-absorption modulation region including an InP buffer layer and a quantum well arranged from bottom to top, and the quantum well is the top layer of the electro-absorption modulation region; the quantum well includes a quantum well substrate layer, a first heterojunction layer, a quantum well and a barrier layer, a second heterojunction layer, a backset layer, and a quantum well top layer stacked on each other; wherein, the waveguide layer of the gain region, the quantum well of the electro-absorption modulation region, and the waveguide layer of the grating region are located on the same layer; the quantum well substrate layer, the backset layer, and the quantum well top layer are made of InP-based materials respectively; a silica layer is filled between the quantum well substrate layer and the metal electrode, between the backset layer and the metal electrode, and between the quantum well top layer and the metal electrode; the electro-absorption modulation region is used for signal modulation of the light beam from the grating region.

2. The laser chip according to claim 1, wherein, A first isolation region is arranged between the gain region and the grating region, and a second isolation region is arranged between the grating region and the electro-absorption modulation region.

3. The laser chip according to claim 1, wherein The quantum well substrate layer is an n-type InP substrate, the first heterojunction layer, the quantum well and the barrier layer, and the second heterojunction layer are all made of InGaAsP materials with a photoluminescence peak of 1170 nm, the backset layer is made of InP material, and the quantum well top layer is a p-type InP material; Wherein the quantum well and the barrier layer include a quantum well region and a barrier region, the quantum well region has a compressive strain of 0.6 - 0.8% and includes 8 groups of quantum wells, and the barrier region has a relaxation strain of 0.2 - 0.4% and includes 8 groups of barriers.

4. The laser chip according to claim 2, wherein The length of the gain region is 375 μm, the length of the grating region is 150 μm, the length of the electro-absorption modulation region is 110 μm, the length of the first isolation region is 45 μm, and the length of the second isolation region is 80 μm.

5. The laser chip according to claim 1, wherein The grating region includes a grating layer and a waveguide layer, the material of the grating layer is InGaAsP material with a photoluminescence peak of 1250 nm and a thickness of 300 Å, and the material of the waveguide layer is InGaAsP material with a photoluminescence peak of 1380 nm and a thickness of 2900 Å.

6. The laser chip according to claim 1, characterized in that, The thickness of the silica layer is 5000 Å.

7. The laser chip according to claim 1, characterized in that, The grating layer is a distributed Bragg reflector formed by holographic exposure.

8. An optical module, characterized in that, Including the laser chip according to any one of claims 1 - 7.

Images