CN118285031A

CN118285031A - Optical module

Info

Publication number: CN118285031A
Application number: CN202280076517.1A
Authority: CN
Inventors: 梁海波; 章力明; 马军涛; 吴名忠
Original assignee: Hisense Broadband Multimedia Technology Co Ltd
Current assignee: Hisense Broadband Multimedia Technology Co Ltd
Priority date: 2021-11-29
Filing date: 2022-06-30
Publication date: 2024-07-02
Also published as: CN114156732A; WO2023093052A1

Abstract

A laser chip and optical module (200), the laser chip integrated with a gain region, a grating region and an electroabsorption modulation region, the gain region producing a beam, the grating region wavelength tuning the beam; the quantum well of the electroabsorption modulation region has a special structural design, so that excellent transmission performance is ensured, and the signal modulation speed is further improved; and meanwhile, silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the reset layer and the metal electrode and between the quantum well top layer and the metal electrode.

Description

Optical module

The present application claims priority from chinese patent application filed at 2021, 11 and 29 to the national intellectual property agency, application number 202111432015.1, entitled "a laser chip and optical module", the entire contents of which are incorporated herein by reference.

Technical Field

The disclosure relates to the technical field of optical communication, and in particular relates to an optical module.

Background

In today's optical fiber transmission systems, the requirements for the light source are getting higher and higher. High-speed, high-integration, wavelength-tunable light sources have been a hotspot in research in the industry, with the following laser chips integrated with electroabsorption modulators, which have the following technical problems: firstly, the signal modulation speed is basically 10G, and cannot reach the high signal modulation speed of 25G, so that the transmission requirement of 10 km cannot be met; second, the inability to integrate wavelength tuning functions results in the need for the simultaneous activation and maintenance of a large number of different signal light sources in a dense wavelength division multiplexing system.

Disclosure of Invention

The embodiment of the disclosure provides a laser chip, which comprises: a gain region for generating a light beam; a grating region for wavelength tuning the light beam from the gain region; the electro-absorption modulation region comprises a quantum well, the quantum well comprises a quantum well substrate layer, a first heterojunction layer, a potential well, a potential barrier layer, a second heterojunction layer, a back layer and a quantum well top layer which are stacked with each other, wherein silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the back layer and the metal electrode and between the quantum well top layer and the metal electrode, and are used for modulating signals of light beams from the grating region.

Drawings

In order to more clearly illustrate the technical solutions of the present disclosure, the drawings that need to be used in some embodiments of the present disclosure will be briefly described below, and it is apparent that the drawings in the following description are only drawings of some embodiments of the present disclosure, and other drawings may be obtained according to these drawings to those of ordinary skill in the art. Furthermore, the drawings in the following description may be regarded as schematic diagrams, not limiting the actual size of the products, the actual flow of the methods, the actual timing of the signals, etc. according to the embodiments of the present disclosure.

Fig. 1 is a connection diagram of an optical communication system according to some embodiments;

Fig. 2 is a block diagram of an optical network terminal according to some embodiments;

FIG. 3 is a block diagram of an optical module according to some embodiments;

fig. 4 is an exploded view of a light module according to some embodiments;

FIG. 5 is a schematic diagram of the appearance of a laser chip according to some embodiments;

FIG. 6 is a schematic diagram of an edge growth structure of a laser chip according to some embodiments;

FIG. 7 is a schematic diagram of a quantum well structure of an electroabsorption modulation region in a laser chip according to some embodiments;

FIG. 8 is a schematic diagram of modulation speed of a laser chip according to some embodiments;

FIG. 9 is a graph showing a laser chip wavelength as a function of injection current according to some embodiments;

Fig. 10 is a schematic diagram of a manufacturing process of a laser chip according to some embodiments.

Detailed Description

The following description of the embodiments of the present disclosure will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by one of ordinary skill in the art based on the embodiments provided by the present disclosure are within the scope of the present disclosure.

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" and its other forms such as the third person referring to the singular form "comprise" and the present word "comprising" are to be construed as open, inclusive meaning, i.e. as "comprising, but not limited to. In the description of the specification, the terms "one embodiment", "some embodiments (some embodiments)", "exemplary embodiment (exemplary embodiments)", "example (example)", "specific example (some examples)", etc. are intended to indicate that a particular feature, structure, material, or characteristic associated with the embodiment or example is 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. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The terms "first" and "second" are used below for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present disclosure, unless otherwise indicated, the meaning of "a plurality" is two or more.

In describing some embodiments, expressions of "coupled" and "connected" and their derivatives may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more elements are in direct physical or electrical contact with each other. As another example, the term "coupled" may be used in describing some embodiments to indicate that two or more elements are in direct physical or electrical contact. However, the term "coupled" or "communicatively coupled (communicatively coupled)" may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the disclosure herein.

At least one of "A, B and C" has the same meaning as at least one of "A, B or C" and includes the following combinations of A, B and C: a alone, B alone, C alone, a combination of a and B, a combination of a and C, a combination of B and C, and a combination of A, B and C.

"A and/or B" includes the following three combinations: only a, only B, and combinations of a and B.

The use of "configured to" herein is meant to be an open and inclusive language that does not exclude devices configured to perform additional tasks or steps.

As used herein, "about," "approximately" or "approximately" includes the stated values as well as average values within an acceptable deviation range of the particular values as determined by one of ordinary skill in the art in view of the measurement in question and the errors associated with the measurement of the particular quantity (i.e., limitations of the measurement system).

In the optical communication technology, light is used to carry information to be transmitted, and an optical signal carrying the information is transmitted to an information processing device such as a computer through an information transmission device such as an optical fiber or an optical waveguide, so as 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 realized. Further, since a signal transmitted by an information transmission device such as an optical fiber or an optical waveguide is an optical signal and a signal that can be recognized and processed by an information processing device such as a computer is an electrical signal, it is necessary to perform mutual conversion between the electrical signal and the optical signal in order to establish an information connection between the information transmission device such as an optical fiber or an optical waveguide and the information processing device such as a computer.

The optical module realizes the function of interconversion between the optical signal and the electric signal in the technical field of optical fiber communication. The optical module comprises an optical port and an electric port, the optical module realizes optical communication with information transmission equipment such as optical fibers or optical waveguides through the optical port, realizes electric connection with an optical network terminal (for example, optical cat) through the electric port, and the electric connection is mainly configured to realize power supply, I2C signal transmission, data signal transmission, grounding and the like. The optical network terminal transmits the electric signal to information processing equipment such as a computer through a network cable or wireless fidelity (Wi-Fi).

Fig. 1 is a connection diagram of an optical communication system according to some embodiments. As shown in fig. 1, 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.

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 (6-8 kilometers), on the basis of which, if a repeater is used, it is theoretically possible to realize ultra-long-distance transmission. Thus, in a typical optical communication system, the distance between the remote server 1000 and the optical network terminal 100 may typically reach several kilometers, tens of kilometers, or hundreds of kilometers.

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 apparatus 2000 may be any one or several of the following: routers, switches, computers, cell phones, tablet computers, televisions, etc.

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 apparatus 2000 and the optical network terminal 100. The connection between the local information processing apparatus 2000 and the remote server 1000 is made by an optical fiber 101 and a network cable 103. And the connection between the optical fiber 101 and the network cable 103 is made by the optical module 200 and the optical network terminal 100.

The optical module 200 includes an optical port and an electrical port. The optical port is configured to connect with the optical fiber 101 such that the optical module 200 establishes a bi-directional optical signal connection with the optical fiber 101. The electrical port is configured to be accessed into the optical network terminal 100 such that the optical module 200 establishes a bi-directional electrical signal connection with the optical network terminal 100. The optical module 200 performs 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, an optical signal from the optical fiber 101 is converted into an electrical signal by the optical module 200 and then input to the optical network terminal 100, and an electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module 200 and input to the optical fiber 101.

The optical network terminal 100 includes a substantially rectangular parallelepiped housing (housing), and an optical module interface 102 and a network cable interface 104 provided on the housing. The optical module interface 102 is configured to access the optical module 200 such that the optical network terminal 100 establishes a bi-directional electrical signal connection with the optical module 200. The network cable interface 104 is configured to access the network cable 103 such that the optical network terminal 100 establishes a bi-directional electrical signal connection with the network cable 103. A connection is established between the optical module 200 and the network cable 103 through the optical network terminal 100. By way of example, since the optical network terminal 100 transmits an electrical signal from the optical module 200 to the network cable 103 and transmits a signal from the network cable 103 to the optical module 200, the optical network terminal 100 can monitor the operation of the optical module 200 as a host computer of the optical module 200. The upper computer of the Optical module 200 may include an Optical line terminal (Optical LINE TERMINAL, OLT) or the like in addition to the Optical network terminal 100.

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.

Fig. 2 is a block diagram of an optical network terminal according to some embodiments, and fig. 2 only shows a structure of the optical network terminal 100 related to the optical module 200 in order to clearly show a connection relationship between the optical module 200 and the optical network terminal 100. As shown in fig. 2, the optical network terminal 100 further includes a PCB circuit board 105 disposed in the housing, a cage 106 disposed on a surface of the PCB circuit board 105, and an electrical connector disposed inside the cage 106. The electrical connector is configured to access an electrical port of the optical module 200. The cage 106 is provided with a radiator 107, and the radiator 107 has a convex portion such as a fin for increasing a heat radiation area.

The optical module 200 is inserted into the cage 106 of the optical network terminal 100, the optical module 200 is fixed by the cage 106, and 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 with an electrical connector inside the cage 106, so that the optical module 200 establishes a bi-directional electrical signal connection with the optical network terminal 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 bi-directional electrical signal connection with the optical fiber 101.

Fig. 3 is a block diagram of an optical module according to some embodiments, and fig. 4 is an exploded view of an optical module according to some embodiments. As shown in fig. 3 and 4, the optical module 200 includes a housing, a circuit board 105 disposed in the housing, and an optical transceiver.

The housing comprises an upper housing 201 and a lower housing 202, the upper housing 201 being folded over the lower housing 202 to form the above-described housing with two openings 204 and 205, the outer contour of the housing generally assuming a square shape.

In some embodiments of the present disclosure, the lower housing 202 includes a bottom plate and two lower side plates disposed at both sides of the bottom plate and perpendicular to the bottom plate. The upper case 201 includes a cover plate, and two upper side plates disposed at two sides of the cover plate and perpendicular to the cover plate, and two side walls are combined with the two side plates to realize that the upper case 201 is covered on the lower case 202.

The direction of the connection line of the two openings 204 and 205 may be identical to the length direction of the optical module 200 or not identical to the length direction of the optical module 200. Illustratively, opening 204 is located at the end of light module 200 (left end of fig. 3) and opening 205 is also located at the end of light module 200 (right end of fig. 3). Or opening 204 is located at the end of light module 200 and opening 205 is located at the side of light module 200. The opening 204 is an electrical port, and the golden finger of the circuit board 105 extends out of the electrical port 204 and is inserted into an upper computer (such as the optical network terminal 100). The opening 205 is an optical port configured to be connected to the external optical fiber 101, so that the optical fiber 101 is connected to an optical transceiver device inside the optical module 200.

By adopting the assembly mode of combining the upper shell 201 and the lower shell 202, devices such as the circuit board 105 and the like are conveniently installed in the shells, and the upper shell 201 and the lower shell 202 can form packaging protection for the devices. In addition, when devices such as the circuit board 105 are assembled, the positioning component, the heat dissipation component and the electromagnetic shielding component of the devices are conveniently arranged, and the automatic implementation and production are facilitated.

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

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

Illustratively, the unlocking member 203 is located on the outer walls of the two lower side plates of the lower housing 202, and includes a snap-in member that mates with the cage of the host computer (e.g., cage 106 of the optical network terminal 100). When the optical module 200 is inserted into the cage of the upper computer, the optical module 200 is fixed in the cage of the upper computer by the clamping component of the unlocking component 203; when the unlocking member 203 is pulled, the engaging member of the unlocking member 203 moves along with the unlocking member, so as to change the connection relationship between the engaging member and the host computer, so as to release the engagement relationship between the optical module 200 and the host computer, and thus the optical module 200 can be pulled out from the cage of the host computer.

The circuit board 105 includes circuit traces, electronic components, and chips, which are connected together by circuit traces according to a circuit design to perform functions such as power supply, electrical signal transmission, and grounding. The electronic components may include, for example, capacitors, resistors, transistors, metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The chips may include, for example, a micro control unit (Microcontroller Unit, MCU), a limiting amplifier (LIMITING AMPLIFIER), a clock data recovery chip (Clock and Data Recovery, CDR), a power management chip, a Digital Signal Processing (DSP) chip.

The circuit board 105 is generally a hard circuit board, and the hard circuit board can also realize a bearing function due to the relatively hard material, for example, the hard circuit board can stably bear chips. The hard circuit board can also be inserted into an electrical connector in the upper computer cage.

The circuit board 105 further includes a gold finger formed on an end surface thereof, the gold finger being composed of a plurality of pins independent of each other. The circuit board 105 is inserted into the cage 106 and is connected by a gold finger to an electrical connector in the cage 106. The golden finger may be disposed on a surface of only one side of the circuit board 105 (for example, an upper surface shown in fig. 4), or may be disposed on surfaces of both upper and lower sides of the circuit board 105, so as to adapt to a situation where the number of pins is large. The golden finger is configured to establish electrical connection with the upper computer to achieve power supply, grounding, I2C signal transmission, data signal transmission and the like. Of course, flexible circuit boards may also be used in some optical modules. The flexible circuit board is generally used in cooperation with the rigid circuit board to supplement the rigid circuit board.

The optical module of the silicon optical structure further includes a silicon optical chip 400, and the silicon optical chip 400 itself has no light source, and the light source assembly 500 serves as an external light source of the silicon optical chip 400. The light source assembly 500 may be a laser box, in which a laser chip is packaged, and emits light to generate a laser beam, and the light source assembly 500 is used to provide the emitted laser to the silicon photonics chip 400. The laser becomes a preferred light source for the optical module and even the optical fiber transmission with better single wavelength characteristic and better wavelength tuning characteristic, but other types of light such as LED light and the like are not generally adopted by common optical communication systems, even if the light source is adopted in a special optical communication system, the characteristics of the light source and the chip components of the light source are greatly different from those of the laser, so that the optical module adopting the laser and the optical module adopting other light sources have great technical differences, and the two types of optical modules can not be considered to be mutually given technical advices by a person skilled in the art.

The bottom surface of the silicon optical chip 400 and the bottom surface of the light source assembly 500 are respectively disposed on the substrate, the silicon optical chip and the light source are in optical connection, the optical path is very sensitive to the positional relationship between the silicon optical chip and the light source, and the materials with different expansion coefficients can cause deformation with different degrees, which is not beneficial to the realization of the preset optical path. In the embodiment of the disclosure, the silicon optical chip and the light source are arranged on the same substrate, and the substrate of the same material is deformed, so that the positions of the silicon optical chip and the light source are equally affected, and the relative positions of the silicon optical chip and the light source are prevented from being greatly changed. Preferably, the expansion coefficient of the substrate material is similar to that of the silicon optical chip and/or the light source material, the main material of the silicon optical chip is silicon, the light source can be made of kovar metal, and the substrate is generally made of silicon or glass.

There are various relationships between the substrate and the circuit board 105, one of which is shown in fig. 4, the circuit board 105 has an opening penetrating through the upper and lower surfaces, and the silicon optical chip and/or the light source are disposed in the opening, so that the silicon optical chip and/or the light source can radiate heat to the upper surface of the circuit board and the lower surface of the circuit board at the same time, the substrate is disposed on one side of the circuit board, and the silicon optical chip and/or the light source penetrates through the opening of the circuit board and is disposed on the heat radiating substrate, so that the substrate has the effects of supporting and radiating heat. In another mode, the circuit board is not provided with an opening, the substrate is arranged on the circuit board, the substrate is arranged on the surface of the circuit board or embedded in the circuit board, and the silicon optical chip and the light source are arranged on the surface of the substrate.

The bottom surface of the light source assembly 500 is disposed on the substrate, and the light source assembly 500 emits light through the side surface, and the emitted light enters the silicon photo chip 400. Silicon is used as a main substrate, silicon is not ideal luminescent material, and the light source cannot be integrated in the silicon optical chip 400, and the external light source assembly 500 is required to provide the light source. The light provided by the light source assembly 500 to the silicon optical chip is emission light with single wavelength and stable power, no data is carried, and the emission light is modulated by the silicon optical chip 400 to realize loading of the data into the emission light.

The bottom surface of the silicon optical chip 400 is disposed on the substrate, and the side surface of the silicon optical chip 400 receives the emitted light from the light source, and modulation of the emitted light and demodulation of the received light are performed by the silicon optical chip. The surface of the silicon optical chip is provided with a bonding pad which is electrically connected with the circuit board through wire bonding. In some embodiments of the present disclosure, the circuit board provides the data signal from the upper computer to the silicon optical chip, the silicon optical chip modulates the data signal into the emitted light, and the received light from the outside is demodulated into an electrical signal by the silicon optical chip and then output to the upper computer through the circuit board.

First optical fiber ribbon 600 and second optical fiber ribbon 700 are each formed from a combination of a plurality of optical fibers, in the disclosed embodiment, first optical fiber ribbon 600 is a transmitting optical fiber ribbon and second optical fiber ribbon 700 is a receiving optical fiber ribbon. One end of the first optical fiber ribbon 600 is connected to the silicon optical chip 400, and the other end is connected to the optical fiber interface 800; one end of the second ribbon 700 is connected to the silicon optical chip 400 and the other end is connected to the fiber interface 800. The fiber interface 800 is connected to an external optical fiber. It can be seen that the optical connection between the silicon optical chip 400 and the optical fiber interface 800 is achieved through the first optical fiber ribbon 600 and the second optical fiber ribbon 700, and the optical fiber interface 800 is achieved to be in optical connection with the optical fiber outside the optical module.

The light source assembly 500 transmits the emission light without carrying the signal into the silicon optical chip 400, and the silicon optical chip 400 modulates the emission light without carrying the signal, loads data into the emission light without carrying the signal, and modulates the emission light without carrying the signal into the emission light with the data signal. The emitted light carrying the data signal is transmitted to the optical fiber interface 800 through the first optical fiber ribbon 600, and is transmitted to the external optical fiber through the optical fiber interface 800, so that the light carrying the data signal is transmitted to the external optical fiber of the optical module, and the conversion of the electrical signal into the optical signal is realized.

The optical signal from the external optical fiber is transmitted to the optical fiber interface 800, and then is transmitted to the silicon optical chip 400 through the second optical fiber ribbon 700, the silicon optical chip 400 demodulates the optical signal into an electrical signal, and the electrical signal is output to the upper computer through the circuit board, so that the optical signal is converted into the electrical signal.

The light source assembly 500 in the embodiments of the present disclosure includes a laser chip, and the surface of the laser chip in the embodiments of the present disclosure is integrated with a gain region, a grating region, and an electroabsorption modulation region. The gain region generates photons and is amplified, the grating region carries out frequency selection on the amplified light waves, the electroabsorption modulation region modulates specific wavelength, and then the output of the laser with the specific wavelength is realized. By changing the current injected into the grating region, the continuous change of the refractive index of the grating region waveguide can be realized, so that light beams with different wavelengths are output. The length design of the electroabsorption modulation area is longer, the electroabsorption modulation area with enough length can ensure enough electroabsorption capacity, the reaction speed of the device is ensured to be fast enough, the signal modulation speed is improved, the quantum well of the electroabsorption modulation area has special structural design, the excellent transmission performance is ensured, and the signal modulation speed is further improved. Meanwhile, silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the reset layer and the metal electrode and between the quantum well top layer and the metal electrode, and the arrangement of the silicon dioxide layers can adjust the capacitance of the chip to obtain smaller parasitic capacitance, so that the signal modulation speed is further improved. The electroabsorption modulation region in the embodiment of the disclosure realizes the 25G signal modulation speed through special design, and meets the requirement of 10 km transmission distance. Therefore, the laser chip in the embodiment of the disclosure is a chip integrating gain, wavelength adjustment and electric signal modulation functions, and has important significance for an optical fiber transmission system.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

FIG. 5 is a schematic diagram of the appearance of a laser chip according to some embodiments; fig. 6 is a schematic diagram of an edge growth structure of a laser chip according to some embodiments.

As shown in fig. 5, in the embodiment of the disclosure, the surface of the laser chip includes a gain region, a grating region and an electroabsorption modulation region, where the gain region and the electroabsorption modulation region are respectively located at two end sides, and the grating region is located between the gain region and the electroabsorption modulation region. The gain region generates photons and is amplified, the grating region carries out frequency selection on the amplified light waves, the electroabsorption modulation region modulates specific wavelength, and then the output of the laser with the specific wavelength is realized. The electroabsorption modulation region can change the absorption loss of light of the electroabsorption modulation region, so that the modulation of an optical signal is realized. The electroabsorption modulation region comprises a quantum well structure, wherein the quantum well structure is formed by stacking materials with different forbidden bandwidths layer by layer.

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 electroabsorption modulation region. As shown in fig. 5, the gain region has a length of 375 μm, the grating region has a length of 150 μm, the electro-absorption modulation region has a length of 110 μm, the first isolation region has a length of 45 μm, and the second isolation region has a length of 80 μm.

As shown in fig. 6, the Gain region includes an InP pad layer, a waveguide layer, a Gain quantum well structure layer, and a P-doped InP layer stacked on top of each other from bottom to top, corresponding to the n-InP substate, buffer layers, waveguide layers, gain MQW/SCH LAYERS layers, and P-InP clad layers, respectively, in the Gain region on the left side of fig. 6.

The grating region includes InP pad layer, grating layer and waveguide layer stacked one above the other from bottom to top, corresponding to n-InP substate, buffer layers, GRATING LAYER layers and waveguide layers, respectively, in the middle grating region of fig. 6.

The electroabsorption modulation region comprises an InP cushion layer and an electroabsorption modulation quantum well structure layer which are stacked from bottom to top, and the n-InP substate, the buffer layers and the Gain MQW/SCH LAYERS layers respectively correspond to the electroabsorption modulation region on the right side of the electroabsorption modulation region in FIG. 6.

In the embodiments of the present disclosure, the first layer, the second layer, and the like are defined in the top-down direction for convenience of description. The first layer, the second layer, the third layer and the fourth layer of the gain region are respectively a p-type doped InP layer, a gain quantum well structure layer, a waveguide layer and an InP cushion layer; the first layer and the second layer of the grating area are empty, the third layer is a waveguide layer, the fourth layer is a grating layer, and the fifth layer is an InP cushion layer; the first layer and the second layer of the electroabsorption modulation region are empty, the third layer and the fourth layer are electroabsorption modulation quantum well structure layers, and the fifth layer is an InP cushion layer. It can be seen that the first layer and the second layer corresponding to the grating region and the electroabsorption modulation region are blank, i.e. the first layer and the second layer of the gain region are blank in the rightward direction, and in fig. 6, the gain region is located on the left side, and the electroabsorption modulation region is located on the right side. Thus, it can be seen that in the embodiments of the present disclosure, the gain region and the grating region adopt an innovative lateral coupling process, rather than a conventional tail-junction growth process, so that the need for one-time outer edge growth is reduced.

Light generated from the gain region quantum well eventually flows laterally into the waveguide layer where wavelength selection is performed.

The embodiment of the disclosure provides a lateral coupling technology, reduces the loss of a gain region to a wavelength adjustment region, and simplifies the process flow.

In the embodiment of the disclosure, the grating region includes a grating layer and a waveguide layer, where the grating layer (labeled as a grafting material in the figure) is InGaAsP material with a photoluminescence peak of 1250nm and has a thickness of 300A (1A is minus ten square meters). The waveguide layer is made of InGaAsP material with a photoluminescence peak of 1380nm and has a thickness of 2900A, and is lightly doped with 2X 1017/cubic centimeter. The setting of the material thickness in the embodiment of the disclosure needs to meet the wavelength modulation range requirement and has small light propagation loss.

The grating is a distributed Bragg reflection grating in the embodiment of the disclosure by changing the current injected into the grating area to output light beams with different wavelengths, and the whole light source chip is subjected to holographic exposure only once to form the grating, so that the period of the grating is fixed. The continuous change of the refractive index of the grating area waveguide can be realized by changing the current injected into the grating area, so that the continuous change of the grating passband is realized, and the Fabry-Perot mode corresponding to the target wavelength is selected.

Compared with the mechanical tuning and the thermal tuning, the electric tuning has a larger wavelength adjusting range, has a faster wavelength switching speed and can meet the requirement of optical fiber communication on a laser. Electrical tuning is achieved by injecting charge carriers into the grating region, thereby changing the refractive index of its material.

Fig. 9 is a graph of laser chip Wavelength as a function of injection current, wherein DBR current on the abscissa represents the laser chip injection current and Wavelength on the ordinate represents the laser chip Wavelength, according to some embodiments. As shown in fig. 9, the laser chip in the embodiment of the disclosure achieves a wavelength change of about 11nm when the current is 50mA, and can cover the requirement of 8nm wavelength change and have a margin.

In summary, in the laser chip of the embodiment of the disclosure, by changing the magnitude of the current injected into the grating region, the refractive index of the grating region waveguide can be continuously changed, so that light beams with different wavelengths are output.

In the embodiment of the disclosure, in order to enable the laser chip to realize the electrical modulation rate at 25GHz and meet the requirement of 10 km for transmission distance, the embodiment of the disclosure has the following special structure for the electrical absorption modulation region:

In some embodiments, the material of the electron well structure of the electroabsorption modulation region is determined by the overall photoluminescence peak position of the electroabsorption region, which is a value of the target wavelength minus 60nm, and the transmission performance is optimized only near this design value, through trial and error. Fig. 7 is a schematic diagram of a quantum well structure of an electroabsorption modulation region in a laser chip according to some embodiments. As shown in fig. 7, the quantum well comprises a quantum well substrate layer, a first heterojunction layer, a potential well, a barrier layer, a second heterojunction layer, a back-off layer and a quantum well top layer which are stacked oppositely, wherein silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the back-off layer and the metal electrode and between the quantum well top layer and the metal electrode. The parameters of each layer are as follows:

The quantum well substrate layer is an n-type InP substrate, the first heterojunction layer is arranged on the quantum well substrate layer, the material is an InGaAsP material with a photoluminescence peak 1170nm, and the thickness is 420A (1A is minus ten times square meters). Above this is 8 sets of potential wells and 8 sets of potential barriers, where the potential well regions have a compression of 0.6-0.8% and the barrier regions have a relaxation of 0.2-0.4%. In one embodiment, the thickness of the 8 sets of wells is 90A, and the design requires 0.7% compression of the well region; the thickness of the 8 group barrier is 50A, the material is InGaAsP material with photoluminescence peak 1170nm, and the design requires 0.3% relaxation of the barrier region. And a second heterojunction layer with the same parameters as the first heterojunction layer. Further above this is an InP setback layer of 800A for diluting the upper in-flowing doping. The top is p-type InP material.

In some embodiments, the electroabsorption modulation region length is 110um, and a sufficiently long electroabsorption modulation region length can ensure sufficient electroabsorption capability so that the extinction ratio of the device meets application requirements; the length of the electroabsorption modulation region is long enough to obtain smaller capacitance and smaller time parameter, thereby improving the reaction speed of the device.

In some embodiments, a silicon dioxide layer is filled between the quantum well substrate layer and the metal electrode, between the setback layer and the metal electrode, and between the quantum well top layer and the metal electrode. The quantum well substrate layer, the back layer and the quantum well top layer are all made of InP materials, and thicker silicon dioxide materials are filled between the InP materials of the chip and the metal electrodes to adjust the capacitance of the chip. In the embodiment of the disclosure, the silicon dioxide layer is made of 5000A thick silicon dioxide, so that smaller parasitic capacitance is obtained, and the device speed is improved. Fig. 8 is a schematic diagram of modulation speed of a laser chip according to some embodiments, and as shown in fig. 8, the 3dB bandwidth of S21 exceeds 17GHz, which can satisfy 25G modulation and transmission applications.

In summary, in the laser chip in the embodiment of the disclosure, the length design of the electroabsorption modulation region is longer, and the electroabsorption modulation region with enough length can ensure enough electroabsorption capability, so that the device reaction speed is ensured to be fast enough, the signal modulation speed is improved, and the quantum well of the electroabsorption modulation region has a special structural design, so that excellent transmission performance is ensured, and the signal modulation speed is further improved. Meanwhile, silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the reset layer and the metal electrode and between the quantum well top layer and the metal electrode, and the arrangement of the silicon dioxide layers can adjust the capacitance of the chip to obtain smaller parasitic capacitance, so that the signal modulation speed is further improved. The electroabsorption modulation region in the embodiment of the disclosure realizes the 25G signal modulation speed through special design, and meets the requirement of 10 km transmission distance.

In the embodiment of the disclosure, three functions of gain, wavelength adjustment and electric signal modulation are concentrated on one laser chip, and meanwhile, the method is suitable for large-scale manufacturing, and a simple and reliable process flow is formed, so that the method has become the most main and bottleneck problems. For this reason, the embodiment of the disclosure provides a preparation process of a laser chip.

In the embodiment of the disclosure, the gain region and the grating region adopt an innovative lateral coupling process instead of a traditional tail joint growth process, so that the need of one-time outer edge growth is reduced. Fig. 10 is a schematic view of a manufacturing process of a laser chip according to some embodiments, as shown in fig. 10, and the method includes:

step one: fig. 10 (1) shows a substrate wafer in which only the grating waveguide layer is present. And forming a grating by a holographic exposure method, and etching the grating-free area to form the form of the figure 10 (2).

Step two: an outer edge growth is carried out, an InP material cushion layer, a waveguide layer (the material is InGaAsP material with photoluminescence peak of 1380nm, 2900A), an InP material stop layer, and a quantum well structure of a gain region are sequentially grown, then p-type doped InP material is carried out, and finally a layer of InGaAsP material with photoluminescence peak of 1250 is formed, so that the mode shown in fig. 10 (3) is formed.

Step three: growing a silicon dioxide thin layer on a wafer, removing the silicon dioxide layers of the grating region and the electric absorption region by dry etching, removing the InGaAsP material with 1250 photoluminescence peaks of the grating region and the electric absorption region and the p-type doped InP material by selective wet etching, and removing all silicon dioxide to form the graph (4).

Step four: by selective wet etching, only the InGaAsP material is etched, and the InP material is not etched, the InGaAsP material having a photoluminescence peak at 1250 in the gain region and the gain quantum well structures in the grating region and the electro-absorption region can be removed, thereby forming the shape of fig. 10 (5). At this time, light generated from the gain region quantum well finally flows laterally into the waveguide layer, and wavelength selection is performed in the grating region. Finally, conventional tail-in process etching and growth are performed in the grating region and the electroabsorption region to form the shape of fig. 10 (6).

The design provides a verified process flow: the lateral coupling technology is adopted, so that the loss from the gain region to the wavelength adjusting region is reduced, the process flow is simplified, the external edge growth times are reduced, and the method is suitable for mass production.

In the laser chip and the optical module provided by the disclosure, the gain area, the grating area and the electroabsorption modulation area are integrated in the laser chip, and the continuous change of the refractive index of the grating area waveguide can be realized by changing the current injected into the grating area, so that light beams with different wavelengths are output. The quantum well of the electroabsorption modulation region has a special structural design, so that excellent transmission performance is ensured, and the signal modulation speed is further improved. And meanwhile, silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the reset layer and the metal electrode and between the quantum well top layer and the metal electrode. The electroabsorption modulation region in the embodiment of the disclosure realizes the 25G signal modulation speed through special design, and meets the requirement of 10 km transmission distance. Therefore, the laser chip in the embodiment of the disclosure is a chip integrating gain, wavelength adjustment and electric signal modulation functions.

According to the laser chip provided by the embodiment of the disclosure, in the first aspect, the 25G signal modulation speed can be realized, and the requirement of a high-speed optical fiber communication network on a 25G light source can be met; in the second aspect, the wavelength adjustment range above 8nm can be realized, and the technology can be transplanted to various wavelengths, which is not limited to dense wavelength division multiplexing application; in a third aspect, faced with the need for complex functional integration, embodiments of the present disclosure provide for a validated process flow: the lateral coupling technology is adopted, so that the loss from the gain region to the wavelength adjusting region is reduced, the process flow is simplified, the external edge growth times are reduced, and the method is suitable for mass production.

The foregoing is merely a specific embodiment of the disclosure, but the protection scope of the disclosure is not limited thereto, and any person skilled in the art who is skilled in the art will recognize that changes or substitutions are within the technical scope of the disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

A laser chip, comprising:

A gain region for generating a light beam;

a grating region for wavelength tuning the light beam from the gain region;

The electro-absorption modulation region comprises a quantum well, the quantum well comprises a quantum well substrate layer, a first heterojunction layer, a potential well, a potential barrier layer, a second heterojunction layer, a back layer and a quantum well top layer which are stacked with each other, wherein silicon dioxide layers are filled between the quantum well substrate layer and the metal electrode, between the back layer and the metal electrode and between the quantum well top layer and the metal electrode, and are used for modulating signals of light beams from the grating region.
The laser chip of claim 1, wherein the gain region comprises an InP pad layer, a waveguide layer, a gain quantum well structure layer, and a p-type doped InP layer stacked on top of each other;

the grating region comprises an InP cushion layer, a grating layer and a waveguide layer which are mutually stacked;

the electroabsorption modulation region comprises an InP cushion layer and a quantum well structure layer which are mutually stacked;

the waveguide layer of the grating region is the top layer of the grating region, and the quantum well structure layer of the electroabsorption modulation region is the top layer of the electroabsorption modulation region;

the waveguide layer of the gain region, the waveguide layer of the grating region and the quantum well structure layer of the electroabsorption modulation region are positioned on the same layer.
The laser chip of claim 1, wherein a first isolation region is disposed between the gain region and the grating region, and a second isolation region is disposed between the grating region and the electroabsorption modulation region.
The laser chip of claim 1, wherein the quantum well substrate layer is an n-type InP substrate, the first heterojunction layer, potential well and barrier layer, and second heterojunction layer are all made of InGaAsP material with photoluminescence peak of 1170nm, the setback layer is InP material, and the quantum well top layer is p-type InP material;

Wherein the potential well and barrier layer comprises a potential well region having a compression of 0.6-0.8% and comprising 8 sets of potential wells and a barrier region having a relaxation of 0.2-0.4% and comprising 8 sets of barriers.
The laser chip of claim 3, wherein the gain region has a length of 375 μm, the grating region has a length of 150 μm, the electro-absorption modulation region has a length of 110 μm, the first isolation region has a length of 45 μm, and the second isolation region has a length of 80 μm.
The laser chip of claim 1, wherein the grating region comprises a grating layer and a waveguide layer, the grating layer material is InGaAsP material with a photoluminescence peak of 1250nm and has a thickness of 300A, and the waveguide layer material is InGaAsP material with a photoluminescence peak of 1380nm and has a thickness of 2900A.
The laser chip of claim 1, wherein the silicon dioxide layer has a thickness of 5000A.
The laser chip of claim 1, wherein the grating layer is a holographic exposed distributed bragg reflection grating.
An optical module comprising the laser chip of any one of claims 1-8.