Wavelength-tunable dual-mode semiconductor laser chip and preparation method thereof

Abstract

The invention discloses a wavelength-tunable dual-mode semiconductor laser chip and a preparation method thereof, and belongs to the technical field of semiconductors. The chip comprises a laser area, an electrical isolation area, an amplification feedback area and two-end film coating areas, a multi-layer growth structure of the chip comprises multiple functional layers, a mode expansion waveguide layer is of a special structure, an ohmic contact layer comprises specific electrode layout, and the two-end film coating areas adopt 1550nm AR films. The preparation method comprises the steps of forming each functional region, and forming the laser region by using holographic exposure and dry etching processes to form the grating layer. On the basis of an InP semiconductor process platform, the integrated level is high, and a middle phase region is omitted, so that dual-mode output is more stable; eBL is adopted to etch the phase shift Bragg grating and the double-end-face AR coating film, so that generation of pure microwave signals in a degenerate mode can be inhibited; dual-mode synchronous or asynchronous tuning can be realized by tuning the injection current ratio, and the dual-mode tuning circuit has the characteristics of low power consumption and high efficiency and is suitable for scenes with high energy efficiency requirements.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a wavelength-tunable dual-mode semiconductor laser chip and a preparation method thereof. Background Art

[0002] Microwave photonics generates, processes, controls and transmits high-frequency microwave signals by combining optical devices and technologies. It has the advantages of large bandwidth, low loss, light weight and anti-electromagnetic interference. It has been widely used in wireless communications, radar, sensing, imaging and instrumentation. An important technical means of microwave photonics technology includes the generation of microwave signals by dual-mode laser beat frequency. The two modes in the laser resonator oscillate in the same cavity, with good phase correlation, and can directly beat frequency to generate stable microwave signals, which are widely used. Therefore, a simple and efficient optical generation method of dual-mode lasers is also crucial. Traditional dual-wavelength lasers can be realized by solid-state lasers and fiber lasers, but the huge system volume is not conducive to the practical development of the device. Semiconductor lasers use semiconductor materials (such as gallium arsenide, indium phosphide, etc.) as laser media. They have the advantages of small size, low cost and easy integration. They are very suitable for realizing small-volume, low-cost dual-wavelength light sources, and have flexible structural design and tuning capabilities. Previously, typical dual-mode semiconductor lasers mostly adopted a three-segment amplified feedback laser solution. Although the middle phase zone is used to regulate and compensate for the phase difference, it often leads to mode confusion and difficulty in control. Moreover, it involves a complex active and passive monolithic integrated structure, which requires complex docking growth technology and quantum well intermixing technology, which can easily lead to quantum well deformation and the introduction of impurities, reducing the yield. Therefore, in order to achieve a simpler and more efficient dual-mode laser, we proposed a two-stage dual-mode semiconductor laser, which suppresses the degenerate mode through the phase-shifted Bragg grating etched by electron beam, and checks the influence of random phase on the end face by coating AR film on both sides. Therefore, during optical feedback, only a pair of pure dual-mode lasers are generated, which greatly increases the signal purity of the beat frequency microwave output by the system. Summary of the invention

[0003] The purpose of the present invention is to provide a wavelength tunable dual-mode semiconductor laser chip and a preparation method thereof. By using an EBL-etched phase-shifted Bragg grating and AR coating, the problem of the amplified feedback laser in the prior art affecting the purity of the photogenerated microwaves due to the degenerate dual mode is avoided, thereby greatly improving the device performance and making the device more compact.

[0004] To achieve the above-mentioned purpose, the present invention provides a wavelength-tunable dual-mode semiconductor laser chip, comprising a laser region DFB, an electrical isolation region, an amplifying feedback region SOA and coating regions at both ends, wherein the electrical isolation region is respectively connected to the laser region and the amplifying feedback region, the laser region and the amplifying feedback region respectively comprise a multilayer growth structure, and the coating regions at both ends are respectively on the outer end surfaces of the laser region and the amplifying feedback region.

[0005] Preferably, the multilayer growth structure includes a substrate layer, a mode expansion waveguide layer, an undoped lower confinement layer, a barrier layer, a quantum well layer, an undoped upper confinement layer, an etch stop layer, a buffer layer, a grating layer, a cladding layer, an energy band transition layer and an ohmic contact layer arranged in sequence from bottom to top.

[0006] Preferably, the substrate layer, the undoped lower confinement layer, the barrier layer, the quantum well layer, the undoped upper confinement layer, the etch stop layer, the buffer layer, the cladding layer and the energy band transition layer are arranged in different regions, and the growth structures belonging to the same layer are connected as a whole.

[0007] Preferably, the mode expansion waveguide layer comprises two waveguide portions which are arranged in parallel and spaced apart along a preset direction, and an arrangement direction of the laser region DFB and the amplification feedback region SOA is perpendicular to the preset direction.

[0008] Preferably, the waveguide portion includes an upper cover portion and a contact portion, the contact portion is arranged on a side of the upper cover portion away from the substrate layer, the upper cover portions adjacently arranged in different regions are integrally connected, and the contact portions adjacently arranged in different regions are independent of each other.

[0009] Preferably, the ohmic contact layer includes a first electrode and a second electrode which are electrically connected; the first electrode covers the contact portion located in the middle, and the second electrode covers a partial area of ​​any one of the contact portions located at both sides.

[0010] Preferably, the coating areas at both ends are coated with 1550nm AR film.

[0011] A method for preparing a wavelength tunable dual-mode semiconductor laser chip comprises the following steps: A laser region, an isolation region and an amplification feedback region are formed; forming the laser region includes: forming a grating layer by adopting holographic exposure and dry etching processes.

[0012] Therefore, the present invention adopts a wavelength tunable dual-mode semiconductor laser chip with the above structure and a preparation method thereof, which has the following beneficial effects: (1) High integration: The present invention is based on the InP semiconductor process platform and only requires two-stage lasers, omitting the intermediate phase zone, making the dual-mode output of the laser more stable and not causing more complex nonlinear phenomena.

[0013] (2) Mode control: The present invention adopts the method of EBL etching phase-shifted Bragg grating + double-end AR coating, which effectively suppresses the occurrence of degenerate modes and can achieve a purer microwave signal.

[0014] (3) Wavelength tuning capability: The present invention can achieve dual-mode synchronous tuning and asynchronous tuning by tuning the injection current ratio of the two-segment laser, providing a more flexible combination for the generation of microwave signals.

[0015] (4) Energy saving and high efficiency: The laser designed in the present invention is not only small in size and highly integrated, but also has the characteristics of low power consumption and high efficiency. It is particularly suitable for application scenarios with high energy efficiency requirements, such as miniaturized microwave radar systems.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a tunable dual-mode semiconductor laser chip device provided by the present invention; Figure 2 A schematic diagram of the lasing principle of a tunable dual-mode semiconductor laser chip provided by the present invention; Figure 3 A schematic diagram of the epitaxial structure of a tunable dual-mode semiconductor laser chip provided by the present invention; Figure 4 is a schematic diagram of a spectrum of a tunable dual-mode semiconductor laser of this embodiment; Figure 5 Schematic diagram of asynchronous tuning of a tunable dual-mode semiconductor laser of this embodiment, wherein (a) shows the absolute position red shift of two wavelengths after the DFB injection current increases, and (b) shows the relative interval change of two wavelengths after the DFB injection current increases; Figure 6 Schematic diagram of synchronous tuning of a tunable dual-mode semiconductor laser of this embodiment, wherein (a) shows the absolute position red shift of two wavelengths after the DFB and SOA injection currents are increased simultaneously, and (b) shows the relative interval change of two wavelengths after the DFB and SOA injection currents are increased simultaneously; Reference numerals 1. Substrate layer; 2. Mode expansion waveguide layer; 3. Undoped lower confinement layer; 4. Barrier layer; 5. Quantum well layer; 6. Undoped upper confinement layer; 7. Etch stop layer; 8. Buffer layer; 9. Grating layer; 10. Cladding layer; 11. Band transition layer; 12. Ohmic contact layer. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example like Figure 1 As shown, the present invention provides a wavelength tunable dual-mode semiconductor laser chip, Figure 1The schematic diagram of the structure of a tunable dual-mode semiconductor laser chip device mainly includes a laser region DFB, an isolation region and a feedback amplifier region SOA. It includes a laser region DFB, an electrical isolation region, an amplifying feedback region SOA and coating regions at both ends. Both the laser region DFB and the amplifying feedback region SOA include the same InP substrate, InGaAsP multi-quantum well structure and single-mode waveguide. The difference is that the laser region DFB includes a Bragg grating, which is used to select a mode to achieve lasing of a specific wavelength, and a phase-shifted Bragg grating needs to be etched by EBL. The amplifying feedback region SOA does not have a Bragg grating. As a traveling wave amplifier, it only provides amplification, and the output waveguide is not designed with a curved structure to prevent the reflected light from being absorbed by the side wall and thus unable to provide an optical feedback effect. The electrical isolation region is arranged between the laser region DFB and the amplifying feedback region SOA, and is connected to the laser region and the amplifying feedback region respectively, and AR film is coated on both sides, and the coating regions at both ends are respectively on the outer end faces of the laser region and the amplifying feedback region. The coating areas at both ends include an anti-reflection film AR@1550nm (AR@1550nm means an anti-reflection (AR) film with anti-reflection function at a wavelength of 1550nm, which can reduce the reflectivity of the end face at this wavelength to below 0.1%, effectively reducing the impact of end face reflection on laser performance), which can reduce the reflectivity of the end face to below 0.1%.

[0021] The multilayer growth structure includes a substrate layer 1, a mode expansion waveguide layer 2, a non-doped lower confinement layer 3, a barrier layer 4, a quantum well layer 5, a non-doped upper confinement layer 6, an etch stop layer 7, a buffer layer 8, a grating layer 9, a cladding layer 10, a band transition layer 11 and an ohmic contact layer 12, which are arranged from bottom to top.

[0022] The substrate layer 1, the undoped lower confinement layer 3, the barrier layer 4, the quantum well layer 5, the undoped upper confinement layer 6, the etch stop layer 7, the buffer layer 8, the cladding layer 10 and the energy band transition layer 11 are arranged in different regions, and the growth structures belonging to the same layer are connected as a whole.

[0023] The mode expansion waveguide layer 2 includes two waveguide parts arranged in parallel and spaced apart along a preset direction, and the arrangement direction of the laser region DFB and the amplification feedback region SOA is perpendicular to the preset direction.

[0024] The waveguide portion includes an upper cover portion and a contact portion, wherein the contact portion is arranged on a side of the upper cover portion away from the substrate, the upper cover portions arranged adjacently in different regions are integrally connected, and the contact portions arranged adjacently in different regions are independent of each other.

[0025] The ohmic contact layer 12 includes a first electrode and a second electrode that are electrically connected; the first electrode covers a contact portion located in the middle, and the second electrode covers a partial area of ​​any contact portion located at both sides.

[0026] The coating areas at both ends use 1550nm AR film.

[0027] The laser chip uses In (1-x) Ga (x) As (y) P (1-y) The quaternary compound is used as a gain medium on the active layer of the device. The active layer is a multi-quantum well structure, which grows alternately according to the distribution of barrier layer-well layer-barrier layer-well layer-barrier layer. According to the different requirements of slope efficiency and saturation power, 2 well layers and 3 barrier layers to 5 well layers and 6 barrier layers are selected. This material is widely used in the field of semiconductor lasers and has excellent bandgap width tunability and outstanding electro-optical conversion efficiency. In this device, the quaternary compound quantum well material can achieve laser emission in different wavelength ranges through precise process adjustment, thereby providing the required wavelength tuning capability for different application scenarios and meeting high-frequency tuning requirements such as microwave photons and laser communications.

[0028] The amplified feedback laser also includes a substrate layer 1, and the laser region and the amplified feedback region are integrated on the same side of the substrate layer 1; the multi-layer growth structure also includes an active layer, and the active layer is a multi-quantum well structure, which grows alternately according to the distribution of barrier layer-well layer-barrier layer-well layer-barrier layer, and is selected from 2 well layers and 3 barrier layers to 5 well layers and 6 barrier layers according to different requirements of slope efficiency and saturation power. The active layer is arranged between the substrate layer 1 and the grating layer 9; the growth structures arranged in different regions and belonging to the same layer use the same material. A primary epitaxial growth is performed on the InP substrate, mainly including the growth of the active region and the grating layer 9. Based on the electron beam lithography method, a waveguide Bragg grating is produced on the primary epitaxial wafer.

[0029] The grating layer 9 is arranged between the etching stop layer 7 and the mode expansion waveguide layer 2. On the substrate with the grating, the InP material is grown again, which is a transitional P-type doping, and the ohmic contact layer 12 material for contacting the metal and the transition layer material for lattice matching transition between the InP material and the ohmic contact layer 12 material are made on the surface.

[0030] The grating layer 9 uses the technology of electron beam exposure to make a π phase-shifted Bragg grating. That is, a phase shift is inserted into the uniform Bragg grating, thereby introducing a desired resonant mode in the band gap of the uniform Bragg grating. Compared with the uniform Bragg grating, a small depression is introduced in the middle of its reflection and transmission spectrum, which is due to the resonant mode caused by the π phase shift. The two peaks of the same height on the uniform Bragg grating delay spectrum mean that if the uniform Bragg grating is used as a laser resonant cavity, there will be two simultaneously lasing modes, also called two degenerate modes.

[0031] An electrical isolation area is set between the laser area and the amplifier feedback area. Photolithography is performed on the manufactured ridge waveguide to produce an electrical isolation pattern and then etch it to remove the high-solubility doped contact layer on the surface. Generally, the etching is performed to a position about half the height of the waveguide so that the resistance between the two is greater than 1000 ohms, thereby reducing electrical crosstalk.

[0032] The method for preparing a wavelength tunable dual-mode semiconductor laser chip provided by the present invention comprises the following steps: (a) Performing primary epitaxial growth on an InP substrate, mainly including the growth of an active region and a grating layer, and fabricating a waveguide Bragg grating on the primary epitaxial wafer based on an EBL lithography method; (b) growing InP material again on the substrate on which the grating is made to cover the grating surface; (c) Oxide growth is performed on the sample surface, and then the ridge waveguide pattern is fabricated based on contact lithography, and the pattern is transferred to the oxide layer by oxide etching; (d) PN burying of the material, that is, epitaxial growth of P-type and N-type InP materials is performed on the surface of the sample in sequence, so that an NPN doping structure can be formed with the N-type InP material of the bottom substrate, which can effectively form electrical insulation and prevent current from passing; (e) removing the surface oxide and burying the contact layer material, mainly transitional P-type doping, and making a contact layer material for contacting the metal on the surface, as well as a transition layer material for lattice matching transition between the InP material and the contact layer material; (f) After epitaxial growth, a double-groove pattern is produced based on contact lithography and then etched to obtain a double-groove structure to limit the current; (g) performing photolithography on the fabricated double groove surface, fabricating an electrical isolation pattern and performing etching to etch away the highly soluble doped contact layer on the surface, thereby electrically isolating the laser region and the amplification feedback region; (h) Surface-grown insulating layer material, usually silicon dioxide, is used to isolate the metal electrode from the device and protect other locations on the device surface from oxidation, and is based on contact lithography and an insulating layer.

[0033] The operating band of the laser part and the amplifier feedback part provided in the embodiment of the present invention can be 1.3 μm or 1.5 μm. Of course, by adjusting the semiconductor gain material, it can also work in other communication bands, which is not limited here. Figure 2 As shown, Figure 2This is a schematic diagram of the lasing principle of a tunable dual-mode semiconductor laser chip. In the DFB laser region, the integrated Bragg grating provides a resonant mode, and due to the addition of a phase shift structure, the generation of degenerate modes is suppressed, so that the original state of good single-mode lasing is maintained. In the amplification feedback region, due to the natural reflectivity of 0.1% between the chip waveguide and the air interface, the reflected light enters the DFB laser region after being amplified in the amplification region, resulting in the generation of another equivalent mode. The effective optical path difference between the two modes corresponds to the wavelength interval of the dual-mode laser, that is, the frequency interval of the microwave signal.

[0034] like Figure 3 As shown, Figure 3 It is a schematic diagram of the epitaxial structure. Each growth structure is marked by taking the multilayer growth structure included in the laser area as an example. Among them: the laser chip adopts a precise epitaxial structure, and the structure includes a substrate layer 1, a mode expansion waveguide layer 2, a non-doped lower confinement layer 3, a barrier layer 4, a quantum well layer 5, a non-doped upper confinement layer 6, an etching stop layer 7, a buffer layer 8, a grating layer 9, a cladding layer 10, a band transition layer 11 and an ohmic contact layer 12. This multilayer structure can effectively improve the gain characteristics and frequency response characteristics of the laser, and exhibit high-efficiency and low-power working performance in various application scenarios. Among them, in the multilayer growth structure, except for the grating layer, the waveguide layer and the electrode layer, the growth structures arranged in different regions and belonging to the same layer are connected as a whole.

[0035] Specifically, the substrate layer 1 is an n-type InP substrate layer with a doping concentration of 2×10 18 cm -3 The n-type InP substrate 1 is placed in a MOCVD device to perform the first epitaxial growth; other layer structures are sequentially grown on the surface of the n-type InP substrate; The mode expansion waveguide layer 2 is an n-type mode expansion waveguide layer, using In (1-x) Ga (x) As (y) P (1-y) The quaternary compound material is designed to match the InP substrate lattice, with a thickness of 4 μm and a concentration gradient of 2×10 17 Gradually to 0.5×10 17 cm -3 ; The etch stop layer 7 is a p-type etch stop layer, using In (1-x) Ga (x) As (y) P (1-y) Quaternary compound material, the composition is designed to match the InP substrate lattice, the thickness is 10μm, and the doping concentration is 5×10 17 Zn; The buffer layer 8 is a p-type buffer layer made of InP material with a thickness of 30 nm and a doping concentration of 5×10 17 Zn; The grating layer 9 is a p-type grating layer, using In (1-x) Ga (x) As (y) P (1-y) Quaternary compound material, the composition is designed to match the InP substrate lattice; the thickness is 0-70nm, and the grating layer thickness is selected under the condition of the selected laser cavity length to ensure that the grating coupling coefficient κL value is 1.5; the doping concentration is 8×10 17 cm -3 Zn; The cladding layer 10 is a p-type cladding layer made of InP material with a thickness of 1.5 μm and a doping concentration of 2×10 18 cm -3 Zn; The energy band transition layer 11 is a p-type energy band transition layer, using In (1-x) Ga (x) As (y) P (1-y) The quaternary compound material is designed to match the InP substrate lattice, with a thickness of 100nm and a concentration gradient of Zn from 3×10 18 Gradient to 5×10 18 cm -3 ; The ohmic contact layer 12 is a p-type ohmic contact layer, which is heavily doped with In 0.53 Ga 0.47 As ternary compound material, thickness is 150nm, doping concentration is 50×10 18 cm -3 Zn.

[0036] The present invention adopts Bragg grating technology, realizes efficient output of a specific central wavelength by designing a precise grating period and using Bragg equation formula (1) for theoretical calculation. In this design, the grating period is calculated to be 242.18 nm, which is suitable for laser output of 1550 nm wavelength, and the effective refractive index of the epitaxial structure at this wavelength is 3.2. Through electron beam lithography (EBL) technology, the Bragg grating can be accurately manufactured, thereby ensuring the stability of the grating's reflection coefficient and spectral response. This structure not only simplifies the body resonant cavity function of traditional solid-state lasers, but also greatly improves the integration of lasers.

[0037] In grating design, the reflection coefficient of the Bragg grating is calculated by coupled mode theory, as shown in formula (2). Here, κ is the coupling coefficient of the grating, γ is the self-coupling coefficient of the grating, is the transmission constant detuning value of the Bragg wavelength, is the effective refractive index difference, is the grating period, L is the laser cavity length, R is the grating reflectivity, is the Bragg wavelength of the grating, and h is the height of the grating layer. The specific expression is as follows: (1); (2); By adjusting the period of the Bragg grating and the grating coupling coefficient, the Q-switched laser array output with different wavelengths can be achieved, further expanding the application range of the laser. In the DFB distributed feedback laser, by introducing a π phase shift structure in the middle position of the Bragg grating, the high stability output of the single longitudinal mode is achieved, such as Figure 3 As shown in Figure 1, better integration is possible because the reflection of the Bragg grating replaces the function of the solid-state laser body resonator.

[0038] The π phase shift structure is introduced in the middle of the Bragg grating of the DFB laser to achieve high stability output of a single longitudinal mode. Under the action of the feedback amplified optical signal, a dual-mode resonant output occurs, and its response spectrum is as follows Figure 4 As shown, the wavelength interval is 1.04nm, and there are two small side modes on each side. This is due to the four-wave mixing effect produced by the SOA in the amplification area. The side mode suppression ratio is greater than 33dB.

[0039] See also Figure 5 In the embodiment, asynchronous tuning of the dual-mode laser can be achieved by tuning the injection current of the DFB part alone, that is, when the overall wavelength is red-shifted, the wavelength spacing gradually increases, and when the PD is received, continuous output of frequency-tuned high-frequency microwave signals can be achieved. Figure 5 (a) shows the absolute position red shift of the two wavelengths as the DFB injection current increases; Figure 5 (b) shows how the relative spacing between the two wavelengths changes as the DFB injection current increases.

[0040] See also Figure 6 In the embodiment, by tuning the injection current of the DFB and SOA parts at a certain speed ratio at the same time, the synchronous tuning of the dual-mode laser can be achieved, that is, when the overall wavelength is red-shifted, the wavelength spacing remains unchanged, and when the PD is received, the single-frequency continuous output of the high-frequency microwave signal can be achieved. Figure 6 (a) shows the absolute position red shift of the two wavelengths as the DFB (0.4nm / step) and SOA (0.1nm / step) injection currents increase simultaneously; Figure 6(b) shows how the relative spacing between the two wavelengths changes as the DFB and SOA injection currents increase simultaneously.

[0041] Therefore, the present invention adopts the above-mentioned wavelength-tunable dual-mode semiconductor laser chip and its preparation method. The laser is not only small in size and highly integrated, but also has the characteristics of low power consumption and high efficiency. It is particularly suitable for application scenarios with high energy efficiency requirements, such as miniaturized microwave radar systems. The present invention is based on the InP semiconductor process platform and only requires a two-segment laser, omitting the middle phase zone, which also makes the dual-mode output of the laser more stable. It will not cause more complex nonlinear phenomena. The method of EBL etching phase-shifted Bragg grating + double-end AR coating is adopted to well suppress the occurrence of degenerate modes and achieve purer microwave signals. The present invention can achieve dual-mode synchronous tuning and asynchronous tuning by tuning the injection current ratio of the two-segment laser, providing a more flexible combination for the generation of microwave signals.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A wavelength tunable dual-mode semiconductor laser chip, characterized in that: It includes a laser region DFB, an electrical isolation region, an amplifier feedback region SOA and coating regions at both ends. The electrical isolation region is connected to the laser region and the amplifier feedback region respectively. The laser region and the amplifier feedback region each include a multilayer growth structure. The multilayer growth structure includes a substrate layer, a mode expansion waveguide layer, a non-doped lower confinement layer, a barrier layer, a quantum well layer, a non-doped upper confinement layer, an etching stop layer, a buffer layer, a grating layer, a cladding layer, an energy band transition layer and an ohmic contact layer arranged in sequence from bottom to top. The coating regions at both ends are respectively on the outer end faces of the laser region and the amplifier feedback region.

2. The wavelength tunable dual-mode semiconductor laser chip according to claim 1, characterized in that: The substrate layer, the undoped lower confinement layer, the barrier layer, the quantum well layer, the undoped upper confinement layer, the etch stop layer, the buffer layer, the cladding layer and the energy band transition layer are arranged in different regions, and the growth structures belonging to the same layer are connected as a whole.

3. The wavelength tunable dual-mode semiconductor laser chip according to claim 1, characterized in that: The mode expansion waveguide layer includes two waveguide parts arranged in parallel and spaced apart along a preset direction, and an arrangement direction of the laser region DFB and the amplification feedback region SOA is perpendicular to the preset direction.

4. The wavelength tunable dual-mode semiconductor laser chip according to claim 3, characterized in that: The waveguide portion includes an upper cover portion and a contact portion, wherein the contact portion is arranged at a side of the upper cover portion away from the substrate layer, the upper cover portions adjacently arranged in different regions are integrally connected, and the contact portions adjacently arranged in different regions are independent of each other.

5. The wavelength tunable dual-mode semiconductor laser chip according to claim 4, characterized in that: The ohmic contact layer includes a first electrode and a second electrode which are electrically connected; the first electrode covers the contact portion located in the middle, and the second electrode covers a partial area of ​​any one of the contact portions located at both sides.

6. The wavelength tunable dual-mode semiconductor laser chip according to claim 1, characterized in that: The coating areas at both ends are coated with 1550nm AR film.

7. A method for preparing a wavelength tunable dual-mode semiconductor laser chip is applied to a wavelength tunable dual-mode semiconductor laser chip as described in any one of 1 to 6, characterized in that: The following steps are involved: forming a laser region, an isolation region and an amplification feedback region; Forming the laser region includes: forming a grating layer by adopting holographic exposure and dry etching processes.

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