A wavelength-tunable dual-mode semiconductor laser chip and its fabrication method

Abstract

This invention discloses a wavelength-tunable dual-mode semiconductor laser chip and its fabrication method, belonging to the field of semiconductor technology. The chip includes a laser region, an electrically isolated region, an amplification feedback region, and two end-coated regions. Its multilayer growth structure contains multiple functional layers, with a special structure for the mode extension waveguide layer, a specific electrode layout for the ohmic contact layer, and a 1550nm AR film used in the end-coated regions. The fabrication method includes forming each functional region; forming the laser region involves holographic exposure and dry etching processes to form the grating layer. This invention is based on an InP semiconductor process platform, featuring high integration, omitting the intermediate phase region for more stable dual-mode output; employing EBL etching of the phase-shifting Bragg grating and dual-end-face AR coating, it can suppress degenerate modes and generate pure microwave signals; dual-mode synchronous or asynchronous tuning can be achieved by tuning the injection current ratio, exhibiting low power consumption and high efficiency, making it suitable for applications with high energy efficiency requirements.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a wavelength-tunable dual-mode semiconductor laser chip and its fabrication method. Background Technology

[0002] Microwave photonics, by combining optical devices and technologies, generates, processes, controls, and transmits high-frequency microwave signals. It boasts advantages such as large bandwidth, low loss, light weight, and resistance to electromagnetic interference, and has been widely applied in wireless communication, radar, sensing, imaging, and instrumentation. An important technique in microwave photonics involves generating microwave signals through beat frequency generation using dual-mode lasers. The two modes within the laser resonant cavity oscillate co-cavity, exhibiting good phase correlation, allowing for direct beat frequency generation of stable microwave signals, which is widely used. Therefore, simple and efficient optical generation methods for dual-mode lasers are crucial. Traditional dual-wavelength lasers can be implemented using solid-state lasers and fiber lasers; however, their large system size hinders their practical application. Semiconductor lasers, using semiconductor materials (such as gallium arsenide and indium phosphide) as the laser medium, offer advantages such as small size, low cost, and ease of integration, making them ideal for realizing small-volume, low-cost dual-wavelength light sources, while also providing flexible structural design and tuning capabilities. Previously, typical dual-mode semiconductor lasers often employed a three-stage amplification feedback laser scheme. While the middle phase region was intended to compensate for phase differences, it frequently led to mode confusion and difficulty in control. Furthermore, the complex active and passive monolithic integrated structures require sophisticated docking growth and quantum well hybridization techniques, which can easily lead to quantum well deformation and the introduction of impurities, reducing yield. Therefore, to achieve a simpler and more efficient dual-mode laser, we propose a two-stage dual-mode semiconductor laser. This involves suppressing degenerate modes through electron beam etching of a phase-shifted Bragg grating and eliminating the influence of random phase at the end faces by depositing AR films on both sides. As a result, only a pair of pure dual-mode lasers are generated during optical feedback, significantly increasing the signal purity of the beat frequency microwave output by the system. Summary of the Invention

[0003] The purpose of this invention is to provide a wavelength-tunable dual-mode semiconductor laser chip and its fabrication method. By using EBL-etched phase-shift Bragg gratings and AR coating, the problem of the purity of photogenerated microwaves being affected by degenerate dual-mode in amplified feedback lasers in the prior art is avoided, thereby significantly improving device performance and making the device more compact.

[0004] To achieve the above objectives, the present invention provides a wavelength-tunable dual-mode semiconductor laser chip, comprising a laser region (DFB), an electrically isolated region, an amplification feedback region (SOA), and two end-coated regions. The electrically isolated region is connected to the laser region and the amplification feedback region, respectively. Both the laser region and the amplification feedback region include multilayer growth structures. The two end-coated regions are located on the outer end faces of the laser region and the amplification feedback region, respectively.

[0005] Preferably, the multilayer growth structure includes, in sequence from bottom to top, a substrate layer, a mode-spreading 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, a band transition layer, and an ohmic contact layer.

[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 band transition layer are disposed in different regions, and the growth structure belonging to the same layer is connected as a whole.

[0007] Preferably, the mode extension waveguide layer includes two waveguide sections arranged parallel to each other 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.

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

[0009] Preferably, the ohmic contact layer includes an electrically connected first electrode and a second electrode; the first electrode covers the contact portion located in the middle position, and the second electrode covers a portion of the contact portion located on either side.

[0010] Preferably, both ends of the coating area are coated with a 1550nm AR film.

[0011] A method for fabricating a wavelength-tunable dual-mode semiconductor laser chip includes the following steps:

[0012] A laser region, an isolation region, and an amplification feedback region are formed; forming the laser region includes forming a grating layer using holographic exposure and dry etching processes.

[0013] Therefore, the wavelength-tunable dual-mode semiconductor laser chip and its fabrication method using the above-described structure have the following beneficial effects:

[0014] (1) High integration: Based on the InP semiconductor process platform, this invention only requires a two-stage laser, omitting the intermediate phase region, which also makes the dual-mode output of the laser more stable. It will not cause more complex nonlinear phenomena.

[0015] (2) Mode control: The present invention adopts the method of EBL etching phase-shifting Bragg grating + double-end AR coating, which effectively suppresses the occurrence of degenerate modes and can achieve a purer microwave signal.

[0016] (3) Wavelength tuning capability: By tuning the injection current ratio of the two-stage laser, the present invention can achieve dual-mode synchronous tuning and asynchronous tuning, providing a more flexible combination for the generation of microwave signals.

[0017] (4) Energy saving and high efficiency: The laser designed in this 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.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 A schematic diagram of a tunable dual-mode semiconductor laser chip device structure provided by the present invention;

[0020] Figure 2 A schematic diagram of the lasing principle of a tunable dual-mode semiconductor laser chip provided by the present invention;

[0021] Figure 3 A schematic diagram of the epitaxial structure of a tunable dual-mode semiconductor laser chip provided by the present invention;

[0022] Figure 4 This is a schematic diagram of the spectrum of a tunable dual-mode semiconductor laser according to this embodiment;

[0023] Figure 5 This is a schematic diagram of asynchronous tuning of a tunable dual-mode semiconductor laser according to this embodiment, wherein (a) shows the redshift of the absolute positions of the two wavelengths after the DFB injection current increases, and (b) shows the change in the relative interval between the two wavelengths after the DFB injection current increases.

[0024] Figure 6 This is a schematic diagram of synchronous tuning of a tunable dual-mode semiconductor laser according to this embodiment, wherein (a) shows the redshift of the absolute positions of the two wavelengths after the injection currents of DFB and SOA are increased simultaneously, and (b) shows the change in the relative interval between the two wavelengths after the injection currents of DFB and SOA are increased simultaneously.

[0025] Figure Labels

[0026] 1. Substrate layer; 2. Mode spreading 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 Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] Example

[0030] like Figure 1 As shown, this invention provides a wavelength-tunable dual-mode semiconductor laser chip. Figure 1This is a schematic diagram of a tunable dual-mode semiconductor laser chip device, mainly comprising a laser region (DFB), an isolation region, and a feedback amplification region (SOA). It includes the DFB, the electrically isolated region, the SOA, and coating regions at both ends. Both the DFB and SOA utilize the same InP substrate, InGaAsP multiple quantum well structure, and single-mode waveguide. The difference lies in the inclusion of a Bragg grating in the DFB for mode selection to achieve lasing at a specific wavelength, requiring EBL etching of the phase-shifted Bragg grating. The SOA lacks a Bragg grating and acts as a traveling-wave amplifier, providing only amplification. Furthermore, the output waveguide is not designed with a curved structure to prevent reflected light from being absorbed by the sidewalls, thus ensuring optical feedback. The electrically isolated region is positioned between the DFB and SOA, connected to both regions, and coated with an AR film on both sides. The coating regions at both ends are located on the outer end faces of the DFB and SOA, respectively. The coating areas at both ends include an antireflective coating AR@1550nm (AR@1550nm indicates an antireflective (AR) film with antireflective 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%.

[0031] The multilayer growth structure includes, in sequence from bottom to top, a substrate layer 1, a mode spreading waveguide layer 2, an undoped lower confinement layer 3, a barrier layer 4, a quantum well layer 5, an undoped 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.

[0032] 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 band transition layer 11 are disposed in different regions and are connected as a whole in the same layer growth structure.

[0033] The mode extension waveguide layer 2 includes two waveguide sections that are parallel and spaced apart along a preset direction, and the laser region DFB and the amplification feedback region SOA are arranged in a direction perpendicular to the preset direction.

[0034] The waveguide section includes an upper cover and a contact section. The contact section is located on the side of the upper cover that is away from the substrate. The upper cover sections located in adjacent areas are integrally connected, while the contact sections located in adjacent areas are independent of each other.

[0035] The ohmic contact layer 12 includes a first electrode and a second electrode that are electrically connected; the first electrode covers the contact portion located in the middle position, and the second electrode covers a portion of either contact portion located on either side.

[0036] Both ends of the coating area use 1550nm AR film.

[0037] 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 has a multi-quantum-well structure, which is grown in an alternating pattern of barrier layer-well layer-barrier layer-well layer-barrier layer. The number of layers is selected from 2 well layers and 3 barrier layers to 5 well layers and 6 barrier layers, depending on the required slope efficiency and saturation power. This material is widely used in semiconductor lasers, exhibiting excellent bandgap tunability and outstanding electro-optic conversion efficiency. In this device, the quaternary compound quantum well material, through precise process control, can achieve laser emission within different wavelength ranges, thus providing the wavelength tuning capability required for various applications, meeting the high-frequency tuning needs of applications such as microwave photonics and laser communication.

[0038] The amplified feedback laser also includes a substrate layer 1, with the laser region and the amplified feedback region integrated on the same side of the substrate layer 1. The multilayer growth structure also includes an active layer, which is a multi-quantum well structure, grown alternately in a barrier-well-barrier-well-barrier distribution, with the number of well layers (2 wells and 3 barriers) to five well layers and six barriers layers selected according to different requirements for slope efficiency and saturation power. The active layer is disposed between the substrate layer 1 and the grating layer 9; growth structures disposed in different regions but belonging to the same layer use the same material. A single epitaxial growth is performed on the InP substrate, mainly including the growth of the active region and the grating layer 9. A waveguide Bragg grating is fabricated on the single epitaxial wafer using electron beam lithography.

[0039] The grating layer 9 is disposed between the etch stop layer 7 and the mode extension waveguide layer 2. InP material is grown again on the substrate on which the grating has been fabricated. It is a transitional P-type doped material, and an ohmic contact layer 12 material for contact with the metal and a transition layer material for lattice matching between the InP material and the ohmic contact layer 12 material are fabricated on the surface.

[0040] Grating layer 9 utilizes electron beam lithography to fabricate a π-phase-shifted Bragg grating. This involves inserting a phase shift into a uniform Bragg grating, thereby introducing a desired resonant mode within its bandgap. Compared to a uniform Bragg grating, its reflection and transmission spectrum exhibits a small dip in the middle, due to the resonant mode introduced by the π-phase shift. The two peaks of equal height in the time delay spectrum of the uniform Bragg grating indicate that if this uniform Bragg grating were used as a laser resonator, two simultaneously emitted modes would exist, also known as two degenerate modes.

[0041] An electrical isolation region is set between the laser region and the amplification feedback region. Photolithography is performed on the fabricated ridge waveguide to create an electrical isolation pattern and then etching it to remove the highly doped contact layer on the surface. Generally, the etching is performed to about half the height of the waveguide, so that the resistance between the two is greater than 1000 ohms, reducing electrical crosstalk.

[0042] The method for fabricating a wavelength-tunable dual-mode semiconductor laser chip provided by the present invention includes the following steps:

[0043] (a) Perform epitaxial growth on an InP substrate, mainly including the growth of the active region and the grating layer, and fabricate waveguide Bragg gratings on the epitaxial wafer based on the EBL lithography method;

[0044] (b) InP material is grown again on the substrate on which the grating has been fabricated to cover the grating surface;

[0045] (c) Oxide growth is performed on the sample surface, then ridge waveguide patterns are fabricated based on contact lithography, and the patterns are transferred to the oxide layer by oxide etching;

[0046] (d) The material is PN buried, that is, P-type and N-type InP materials are epitaxially grown sequentially on the surface of the sample. This can form an NPN doped structure with the N-type InP material on the bottom substrate, which can effectively form electrical insulation and prevent current from passing through.

[0047] (e) Remove the surface oxide and bury the contact layer material, which is mainly transitional P-type doped, and fabricate a contact layer material for contacting the metal and a transition layer material for lattice matching transition between the InP material and the contact layer material on the surface.

[0048] (f) After epitaxial growth, a double-groove pattern is fabricated based on contact photolithography and etched to obtain a double-groove structure, which restricts the current.

[0049] (g) Photolithography is performed on the fabricated double groove surface to create an electrically isolated pattern and then etch it to remove the highly doped contact layer on the surface, thereby electrically isolating the laser region and the amplification feedback region.

[0050] (h) Surface-grown insulating layer material, typically silicon dioxide, is used to isolate the metal electrodes and devices and to protect other parts of the device surface from oxidation, based on contact lithography and insulating layer.

[0051] The laser section and amplification feedback section provided in this embodiment of the invention can operate in the 1.3μm or 1.5μm wavelength band. Of course, by adjusting the semiconductor gain material, they can also operate in other communication wavelength bands; this is not limited here. Figure 2 As shown, Figure 2 This diagram illustrates the lasing principle of a tunable dual-mode semiconductor laser chip. In the DFB laser region, an integrated Bragg grating provides a resonant mode. Furthermore, the addition of a phase-shifting structure suppresses the generation of degenerate modes, maintaining a good original single-mode lasing state. In the amplification feedback region, due to the natural 0.1% reflectivity at the chip waveguide-air interface, the reflected light is amplified in the amplification region before entering the DFB laser region, leading to the generation of another equivalent mode. The effective optical path difference between these two modes corresponds to the wavelength interval of the dual-mode laser, i.e., the frequency interval of the microwave signal.

[0052] like Figure 3 As shown, Figure 3 This is a schematic diagram of the epitaxial structure. Taking the multilayer growth structure of the laser region as an example, each growth structure is labeled. The laser chip employs a precise epitaxial structure, which includes a substrate layer 1, a mode-spreading waveguide layer 2, an undoped lower confinement layer 3, a barrier layer 4, a quantum well layer 5, an undoped upper confinement layer 6, an etch stop layer 7, a buffer layer 8, a grating layer 9, a cladding layer 10, a bandgap transition layer 11, and an ohmic contact layer 12. This multilayer structure effectively improves the laser's gain and frequency response characteristics, exhibiting high efficiency and low power consumption in various application scenarios. Except for the grating layer, waveguide layer, and electrode layer, the growth structures located in different regions and belonging to the same layer are integrally connected.

[0053] Specifically, substrate 1 is an n-type InP substrate with a doping concentration of 2 × 10⁻⁶. 18 cm -3 The Si layer is formed by placing an n-type InP substrate 1 in an MOCVD apparatus for the first epitaxial growth; other layer structures are then grown sequentially on the surface of the n-type InP substrate.

[0054] Mode-spreading waveguide layer 2 is an n-type mode-spreading waveguide layer, using In... (1-x) Ga (x) As (y) P (1-y) A quaternary compound material, with a composition designed to match the InP substrate lattice, has a thickness of 4 μm and is doped with Si at a gradually increasing concentration, from 2 × 10⁻⁶ at the bottom to the top. 17 Gradient to 0.5×10 17 cm -3 ;

[0055] Etching stop layer 7 is a p-type etch stop layer, using In... (1-x) Ga (x) As (y) P (1-y) A quaternary compound material, with a composition designed to match the InP substrate lattice, has a thickness of 10 μm and a doping concentration of 5 × 10⁻⁶.17 Zn;

[0056] 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 × 10⁻⁶. 17 Zn;

[0057] Grating layer 9 is a p-type grating layer, using In... (1-x) Ga (x) As (y) P (1-y) The quaternary compound material is designed with a composition that matches the InP substrate lattice; its thickness ranges from 0 to 70 nm, with the grating layer thickness selected based on the chosen laser cavity length to ensure a grating coupling coefficient κL of 1.5; and its doping concentration is 8 × 10⁻⁶. 17 cm -3 Zn;

[0058] Cladding 10 is a p-type cladding layer made of InP material, with a thickness of 1.5 μm and a doping concentration of 2 × 10⁻⁶. 18 cm -3 Zn;

[0059] Band transition layer 11 is a p-type band transition layer, using In (1-x) Ga (x) As (y) P (1-y) A quaternary compound material, with a composition designed to match the InP substrate lattice, has a thickness of 100 nm and is doped with Zn at a gradually increasing concentration, from 3 × 10⁻⁶ at the bottom to the top. 18 Gradient to 5×10 18 cm -3 ;

[0060] Ohmic contact layer 12 is a p-type ohmic contact layer, using heavily doped In. 0.53 Ga 0.47 As ternary compound material, with a thickness of 150 nm and a doping concentration of 50 × 10⁻⁶. 18 cm -3 Zn.

[0061] This invention employs Bragg grating technology, achieving efficient output at a specific center wavelength through precise grating period design and theoretical calculations using Bragg's equation (1). In this design, the grating period is calculated to be 242.18 nm, suitable for laser output at a wavelength of 1550 nm, while the effective refractive index of the epitaxial structure at this wavelength is 3.2. The Bragg grating is precisely manufactured using electron beam lithography (EBL) technology, ensuring the stability of the grating's reflection coefficient and spectral response. This structure not only simplifies the bulk resonator function of traditional solid-state lasers but also significantly improves the laser's integration density.

[0062] In grating design, the reflection coefficient of the Bragg grating is calculated using coupled-mode theory, as shown in formula (2). Here, κ Let γ be the coupling coefficient of the grating, and γ be the self-coupling coefficient of the grating. It is the detuning value of the transmission constant of the Bragg wavelength. For effective refractive index difference, For the grating period, L For the laser cavity length, R For grating reflectivity, Let λ be the Bragg wavelength of the grating, and h be the height of the grating layer. The specific expression is as follows:

[0063] (1);

[0064] (2);

[0065] By adjusting the period and coupling coefficient of the Bragg grating, Q-switched laser arrays with different wavelengths can be output, further expanding the application range of lasers. In DFB distributed feedback lasers, high-stability single-longitudinal-mode output is achieved by introducing a π-phase-shift structure at the middle position of the Bragg grating, such as... Figure 3 As shown, since the reflection of the Bragg grating replaces the function of the solid-state laser's bulk resonator, better integration can be achieved.

[0066] By introducing a π-phase shift structure at the center of the Bragg grating in the DFB laser, high-stability single-mode output was achieved. Under the influence of the feedback-amplified optical signal, dual-mode resonant output occurred, and its response spectrum is as follows: Figure 4 As shown, the wavelength spacing is 1.04 nm, with two small side modes on each side. This is due to the four-wave mixing effect generated by the SOA in the amplification region. The side mode rejection ratio is greater than 33 dB.

[0067] See Figure 5 In this embodiment, by individually tuning the injection current of the DFB section, asynchronous tuning of the dual-mode laser can be achieved. That is, with the overall wavelength redshifted, the wavelength spacing gradually increases, and with PD reception, continuous output of frequency-tuned high-frequency microwave signals can be achieved. Figure 5 (a) shows the redshift of the absolute positions 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.

[0068] See Figure 6In this embodiment, by simultaneously tuning the injection currents of the DFB and SOA sections according to a certain speed ratio, synchronous tuning of the dual-mode laser can be achieved. That is, while the overall wavelength is red-shifted, the wavelength spacing remains unchanged. With PD reception, single-frequency continuous output of high-frequency microwave signals can be achieved. Figure 6 (a) shows the redshift of the absolute positions of the two wavelengths as the injection current of both DFB (0.4 nm / step) and SOA (0.1 nm / step) increases simultaneously; Figure 6 (b) shows the change in the relative spacing of the two wavelengths as the injection currents of DFB and SOA increase simultaneously.

[0069] Therefore, this invention employs a wavelength-tunable dual-mode semiconductor laser chip and its fabrication method, as described above. This laser is not only small in size and highly integrated, but also features low power consumption and high efficiency, making it particularly suitable for applications with high energy efficiency requirements, such as miniaturized microwave radar systems. Based on the InP semiconductor process platform, this invention requires only a two-stage laser, omitting the intermediate phase region and making the dual-mode output of the laser more stable. It avoids causing more complex nonlinear phenomena. The use of EBL etching of the phase-shifting Bragg grating and double-end AR coating effectively suppresses the occurrence of degenerate modes, resulting in a purer microwave signal. By tuning the injection current ratio of the two-stage laser, this invention can achieve both synchronous and asynchronous dual-mode tuning, providing a more flexible combination for microwave signal generation.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for fabricating a wavelength-tunable dual-mode semiconductor laser chip, characterized in that, The chip includes a laser region (DFB), an electrical isolation region, an amplification feedback region (SOA), and two end-coated regions. The electrical isolation region is connected to the laser region and the amplification feedback region, respectively. Both the laser region and the amplification feedback region include multilayer growth structures. The two end-coated regions are located on the outer end faces of the laser region and the amplification feedback region, respectively. Its preparation method includes the following steps: This forms the laser region, isolation region, and amplification feedback region; Forming the laser region includes: forming a grating layer using holographic exposure and dry etching processes; The multilayer growth structure includes, in sequence from bottom to top, a substrate layer, a mode-spreading 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 cladding layer, a band transition layer, and an ohmic contact layer; the multilayer growth structure of the laser region also includes a grating layer, which is disposed between the buffer layer and the cladding layer. 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 band transition layer are disposed in different regions, and the growth structure belonging to the same layer is connected as a whole; The mode extension waveguide layer includes two waveguide sections that are parallel and spaced apart along a preset direction. The waveguide portion includes an upper cover portion and a contact portion. The contact portion is disposed on the side of the upper cover portion away from the substrate layer. The upper cover portions disposed adjacently in different regions are integrally connected, and the contact portions disposed adjacently in different regions are independent of each other. Both ends of the coating area are coated with 1550nm AR film; By employing EBL etching of phase-shifted Bragg gratings and double-end AR coating, degenerate modes can be suppressed to generate pure microwave signals.

2. The method for fabricating a wavelength-tunable dual-mode semiconductor laser chip according to claim 1, characterized in that, The arrangement direction of the laser region DFB and the amplification feedback region SOA is perpendicular to the preset direction.

3. The method for fabricating a wavelength-tunable dual-mode semiconductor laser chip according to claim 1, characterized in that, The ohmic contact layer includes a first electrode and a second electrode that are electrically connected; the first electrode covers the contact portion located in the middle position, and the second electrode covers a portion of the contact portion located on either side.

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