A high amplification power and high coupling efficiency semiconductor optical amplifier waveguide structure

Abstract

This invention proposes a high-power, high-coupling-efficiency semiconductor optical amplifier waveguide structure, comprising a first waveguide (8), a second waveguide (9), and a third waveguide (10) arranged sequentially. The first waveguide is a straight waveguide region located at the light input end of the waveguide structure; the third waveguide is a straight waveguide region located at the light output end of the waveguide structure; and the second waveguide is an adiabatic waveguide region with a ridge width that varies as a high-order continuous function. In the direction of light propagation, the width of the adiabatic waveguide region gradually increases from narrow to wide, and the curvature at the beginning / end of the adiabatic waveguide region is the same as the curvature of the straight waveguide regions before and after the adiabatic waveguide region, respectively. The ridge width of the adiabatic waveguide region gradually changes, and the waveguide width at the beginning / end of the adiabatic waveguide region is the same as the width of the straight waveguide regions before and after the adiabatic waveguide region. This invention can significantly improve the power amplification and coupling efficiency of the SOA.

Description

Technical Field

[0001] This invention relates to the field of optical amplifier technology, and in particular to a semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency. Background Technology

[0002] A semiconductor optical amplifier (SOA) is essentially a mirrorless laser. It is a chip-based device that uses a semiconductor gain medium (usually indium phosphide (InP)) to achieve optical amplification through stimulated emission.

[0003] Compared with traditional fiber optic amplifiers, semiconductor optical amplifiers have significant advantages such as small size, low power consumption, easy integration, and adjustable operating wavelength range, making them particularly suitable for applications requiring miniaturization and high-density integration.

[0004] Despite the many advantages of SOA, its performance in large-scale commercial applications is still constrained by two interrelated key technical bottlenecks: insufficient amplified optical power and low fiber coupling efficiency. These two problems seriously affect the system application efficiency and economic benefits of SOA.

[0005] Currently, apart from epitaxial structure design, the main technical approaches to improving SOA amplification power and coupling efficiency are as follows:

[0006] 1. Tapered Waveguide Structure: A narrow waveguide at the input end improves mode purity, while the output end gradually widens into a large optical cavity, reducing power density, suppressing nonlinear and thermal effects, and increasing saturated output power. While the tapered waveguide structure significantly improves the amplification power of the SOA, the rapidly changing tapered structure can excite higher-order modes and even couple energy into the radiation mode, causing additional losses. This not only reduces the expected output power but also leads to deterioration in output beam quality and increased polarization dependence. Furthermore, the size of the tapered tip is typically in the submicron or even nanometer range; minute deviations in photolithography and etching processes can drastically alter the mode field, causing performance to deviate significantly from design expectations, making it difficult to guarantee performance consistency.

[0007] 2. Nonlinear Bending Waveguide Structure: The radius of curvature of a nonlinear bending waveguide changes continuously from the starting point to the ending point (usually increasing smoothly from 0 or a minimum value to a maximum value and then decreasing). Parabolic, exponential, and logarithmic functions are often used. Bending loss can be reduced by controlling the rate of change of curvature. However, nonlinear bending waveguide structures are sensitive to manufacturing errors. Small deviations during cleavage can change the incident and exit angles of the actual starting and ending points, resulting in changes in the mode field distribution and excitation of higher-order modes or radiation modes.

[0008] 3. Monolithic Integration Solution: The monolithic integration solution integrates SOA (Service-Oriented Architecture) with passive waveguides, modulators, detectors, and other devices onto a single chip. On-chip waveguide interconnects significantly reduce coupling losses and alignment difficulties associated with discrete components, fundamentally solving the coupling bottleneck of discrete devices. However, monolithic InP (In-Package) integration has extremely high R&D and manufacturing costs. A single fabrication involves multiple devices, and a design error in any single device can lead to the failure of the entire chip, resulting in high risk, long debugging cycles, and difficulty in independently and efficiently cooling individual devices on a monolithic chip, greatly impacting chip reliability. Although on-chip coupling avoids the significant losses associated with fiber optic connections, mode field matching between different functional devices remains a challenge. Summary of the Invention

[0009] This invention proposes a semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency, which can significantly improve the amplification power and coupling efficiency of SOA.

[0010] The present invention adopts the following technical solution.

[0011] A high-power, high-coupling-efficiency semiconductor optical amplifier waveguide structure is provided. The waveguide structure includes a first waveguide (8), a second waveguide (9), and a third waveguide (10) arranged sequentially. The first waveguide is a straight waveguide region located at the light input end of the waveguide structure. The third waveguide is a straight waveguide region located at the light output end of the waveguide structure. The second waveguide is an adiabatic waveguide region with a ridge width that varies as a high-order continuous function. In the direction of light propagation, the width of the adiabatic waveguide region gradually increases from narrow to wide. The curvature at the beginning and end of the adiabatic waveguide region is the same as the curvature of the straight waveguide regions before and after the adiabatic waveguide region. The ridge width of the adiabatic waveguide region gradually changes, and the waveguide width at the beginning and end of the adiabatic waveguide region is the same as the width of the straight waveguide regions before and after the adiabatic waveguide region.

[0012] When a semiconductor optical amplifier is working, it uses an optical fiber or an input waveguide as the optical input end. The first waveguide and the third waveguide serve as mode conversion components, which slowly convert the mode field size of the light injected at the optical input end into the size that best matches the active region of the semiconductor optical amplifier (SOA), thereby increasing the optical power density in the nonlinear interaction region and improving the efficiency of the nonlinear effect.

[0013] After the injected light enters the waveguide structure, it undergoes stable single-mode amplification at the first waveguide and then power amplification at the second waveguide to reduce the probability of higher-order mode excitation.

[0014] The widths of the first and third waveguides are the same as the width of the input optical end of the second waveguide, and the curvatures at their junctions are the same.

[0015] The second waveguide is a high-order continuous nonlinear adiabatic waveguide. When the second waveguide is used in a chip employing an RWG structure, the high-order continuous variation of the second waveguide ridge width is expressed as a high-order continuous function.

[0016] ,

[0017] In the formula, / Cavity length of the chip,

[0018] In the formula, the higher-order continuous function is used to define the variation trend of the second waveguide ridge width, which is the waveguide edge curve.

[0019] The second waveguide is an axisymmetric structure whose width gradually increases in the optical transmission direction. It is used to compensate for aberrations and improve mode purity, thereby further improving the fiber coupling efficiency of the semiconductor optical amplifier.

[0020] When designing the waveguide structure, the first waveguide and the third waveguide are used to prevent calculation errors, so as to avoid deviations between the actual waveguide and the design value, which would affect the output power and coupling efficiency.

[0021] In the optical amplifier, the combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure. The fabrication process of the monolithic waveguide structure is as follows: first, a top-view pattern of the ridge waveguide pattern is designed; then, a photomask is drawn according to the designed ridge waveguide pattern; then, the waveguide pattern is transferred from the photomask to the photoresist through photolithography; then, the pattern is transferred from the photoresist to the silicon dioxide mask through etching; and finally, the pattern formed on the silicon dioxide mask is transferred to the wafer through etching to form the required monolithic waveguide structure.

[0022] The monolithic waveguide structure is provided with the following components in sequence: InP substrate (1), InP buffer layer (2), InGaAsP / InP high-fold layer (3), N-side wavelength gradient InGaAsP SCH layer (4), strained InGaAsP quantum well active region (5), P-side wavelength gradient InGaAsP SCH layer (6), and InGaAsP etch cutoff layer (7).

[0023] In the fabrication of monolithic waveguide structures, the InP substrate serves as a crystal growth support, providing structural support for the epitaxial layer.

[0024] InP buffer layers are used to alleviate lattice mismatch between the substrate and the epitaxial layer, thereby improving the growth quality of epitaxial materials;

[0025] InGaAsP / InP high-flush layers are used to reduce the optical confinement factor, ensuring that most of the optical power is effectively amplified in the active region. The high-flush layers also help maintain the stable transmission of the fundamental mode, suppress the generation of higher-order modes, and improve the quality of the output beam.

[0026] The SCH layer of N-side wavelength-gradient InGaAsP and the SCH layer of P-side wavelength-gradient InGaAsP together form a double heterojunction, forming a wavelength-gradient structure to enable band continuity, reduce interface defects, improve hole injection efficiency and MQW carrier uniformity, and further improve carrier transport efficiency.

[0027] The strained InGaAsP quantum well active region employs a structure comprising six quantum wells and five quantum barriers, providing the chip with the required gain while adjusting the quantum well width to achieve the desired wavelength range.

[0028] When the chip adopts an RWG structure, the InGaAsP etching stop layer is used to ensure that the etching depth matches the design value during the etching process.

[0029] When it is necessary to optimize the heat dissipation of the amplifier, the heat dissipation capacity of the amplifier can be increased by thinning the InP substrate. After thinning, the remaining thickness of the InP substrate should be 110-120um.

[0030] The chip has a cavity length ranging from 2500 to 2620 μm and a width ranging from 550 to 650 μm.

[0031] like Figure 3 As shown in d, the length of the straight waveguide region of the first waveguide ranges from 160 to 170 μm; the length of the higher-order continuously varying ridge width gradient adiabatic waveguide region of the second waveguide ranges from 2300 to 2400 μm; and the length of the straight waveguide region of the third waveguide ranges from 40 to 50 μm.

[0032] The ridge width of the straight waveguide region 10 of the third waveguide is 9~10um, so that the first and third waveguides can slowly convert the mode field size of the optical fiber or input waveguide to the size that best matches the active region of SOA, thereby increasing the optical power density of the nonlinear interaction region, improving the efficiency of nonlinear effects, and effectively preventing the deviation between the actual waveguide and the design value caused by cleavage error, which affects the output power and coupling efficiency.

[0033] The height range of the first, second, and third waveguides is 2.2~2.5µm.

[0034] The widths of the first and third waveguides are the same as the width of the input optical end of the second waveguide, and the curvatures at their connection points are the same.

[0035] The combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure, and the waveguide tilt angle is 6~7°. The narrow ridge end of the monolithic waveguide structure is the light input end (11), and the wide ridge end is the light output end (12).

[0036] This invention proposes a semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency, solving the problem in existing technologies that cannot achieve both high amplification power and high coupling efficiency. This patented high-power, high-coupling-efficiency semiconductor optical amplifier waveguide structure can significantly improve the amplification power and coupling efficiency of SOA (Optical Optical Amplifier), making it suitable for applications with high requirements for amplification power and coupling efficiency, such as fiber optic communication, laser processing and industrial manufacturing, optoelectronic sensing and lidar.

[0037] This invention addresses the problems of insufficient output power and low fiber coupling efficiency in current SOA (Optical Optical Amplifier) ​​systems by proposing a three-segment waveguide structure with high amplification power and high coupling efficiency. A matching straight waveguide is added before and after a thermally adiabatic waveguide with a gradually widening ridge of a high-order continuous function. The thermally adiabatic waveguide with the gradually widening ridge transitions from narrow to wide, and its curvature at the beginning / end is the same as that of the preceding and following straight waveguides. The waveguide width at the beginning / end of the thermally adiabatic waveguide with the gradually widening ridge is the same as the width of the preceding and following straight waveguides. This waveguide structure for semiconductor optical amplifiers offers advantages such as simple structure, high amplification power, good single-mode characteristics, high fiber coupling efficiency, and high tolerance to manufacturing errors.

[0038] The advantages of this invention also include:

[0039] 1. The high-power, high-coupling-efficiency semiconductor optical amplifier waveguide structure proposed in this invention adopts a straight waveguide plus a nonlinear waveguide plus a straight waveguide structure. The straight waveguides added before and after can act as mode converters, slowly converting the mode field size of the optical fiber or input waveguide to the size that best matches the active region of the SOA, thereby increasing the optical power density in the nonlinear interaction region and improving the efficiency of the nonlinear effect. The straight waveguide before the nonlinear waveguide allows the injected light to undergo stable single-mode amplification first, and then power amplification through the adiabatic waveguide, which reduces the probability of higher-order mode excitation.

[0040] 2. The present invention proposes a high-power and high-coupling-efficiency semiconductor optical amplifier waveguide structure. The second waveguide structure adopts a high-order continuous nonlinear thermally adiabatic waveguide, which compensates for aberrations and improves mode purity, thereby further improving the fiber coupling efficiency of the semiconductor optical amplifier.

[0041] 3. The semiconductor optical amplifier waveguide structure proposed in this invention, which has high amplification power and high coupling efficiency, can effectively prevent deviations between the actual waveguide and the design value caused by cleavage errors by adding a straight waveguide section before and after the nonlinear waveguide, thus affecting the output power and coupling efficiency. Attached Figure Description

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0043] Appendix Figure 1This is a schematic diagram of the waveguide structure of a high-power, high-coupling-efficiency semiconductor optical amplifier in an embodiment of the present invention;

[0044] Appendix Figure 2 This is a top view schematic diagram of the integral waveguide structure in an embodiment of the present invention;

[0045] Appendix Figure 3 These are schematic diagrams of different waveguide structures in embodiments of the present invention ((a) is a tilted straight waveguide; (b) is a tapered waveguide; (c) is a high-order continuous function waveguide without straight waveguides at the front and back; (d) is the waveguide structure proposed in this invention, namely, a straight waveguide + a high-order continuous waveguide + a straight waveguide).

[0046] Appendix Figure 4 In the embodiments of the present invention, under the same epitaxial structure, the same injection power, the same test temperature and current, the corresponding Figure 2 A table showing the test results of amplification power, coupling efficiency, and fiber output power for four waveguide structures;

[0047] In the figure: 1. InP substrate; 2. InP buffer layer; 3. InGaAsP / InP high-refractive-index layer (4 pairs of InGaAsP / InP high-refractive-index layers); 4. N-side wavelength-gradient InGaAsP SCH layer; 5. Strained InGaAsP quantum well active region; 6. P-side wavelength-gradient InGaAsP SCH layer; 7. InGaAsP etched cutoff layer; 8. First waveguide (straight waveguide region); 9. Second waveguide (high-order continuous function changing adiabatic waveguide region); 10. Third waveguide (straight waveguide region); 11. Input end; 12. Output end. Detailed Implementation

[0048] As shown in the figure, a high-power, high-coupling-efficiency semiconductor optical amplifier waveguide structure is disclosed. The waveguide structure includes a first waveguide 8, a second waveguide 9, and a third waveguide 10 arranged sequentially. The first waveguide is a straight waveguide region located at the light input end of the waveguide structure. The third waveguide is a straight waveguide region located at the light output end of the waveguide structure. The second waveguide is an adiabatic waveguide region with a ridge width that varies as a high-order continuous function. In the direction of light propagation, the width of the adiabatic waveguide region gradually increases from narrow to wide, and the curvature at the beginning / end of the adiabatic waveguide region is the same as the curvature of the straight waveguide regions before and after the adiabatic waveguide region, respectively. The ridge width of the adiabatic waveguide region gradually changes, and the waveguide width at the beginning / end of the adiabatic waveguide region is the same as the width of the straight waveguide regions before and after the adiabatic waveguide region.

[0049] When a semiconductor optical amplifier is working, it uses an optical fiber or an input waveguide as the optical input end. The first waveguide and the third waveguide serve as mode conversion components, which slowly convert the mode field size of the light injected at the optical input end into the size that best matches the active region of the semiconductor optical amplifier (SOA), thereby increasing the optical power density in the nonlinear interaction region and improving the efficiency of the nonlinear effect.

[0050] After the injected light enters the waveguide structure, it undergoes stable single-mode amplification at the first waveguide and then power amplification at the second waveguide to reduce the probability of higher-order mode excitation.

[0051] The widths of the first and third waveguides are the same as the width of the input optical end of the second waveguide, and the curvatures at their junctions are the same.

[0052] The second waveguide is a high-order continuous nonlinear adiabatic waveguide. When the second waveguide is used in a chip employing an RWG structure, the high-order continuous variation of the second waveguide ridge width is expressed as a high-order continuous function.

[0053] ,

[0054] In the formula, / Cavity length of the chip,

[0055] In the formula, the higher-order continuous function is used to define the variation trend of the second waveguide ridge width, which is the waveguide edge curve.

[0056] The second waveguide is an axisymmetric structure whose width gradually increases in the optical transmission direction. It is used to compensate for aberrations and improve mode purity, thereby further improving the fiber coupling efficiency of the semiconductor optical amplifier.

[0057] When designing the waveguide structure, the first waveguide and the third waveguide are used to prevent calculation errors, so as to avoid deviations between the actual waveguide and the design value, which would affect the output power and coupling efficiency.

[0058] In the optical amplifier, the combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure. The fabrication process of the monolithic waveguide structure is as follows: first, a top-view pattern of the ridge waveguide pattern is designed; then, a photomask is drawn according to the designed ridge waveguide pattern; then, the waveguide pattern is transferred from the photomask to the photoresist through photolithography; then, the pattern is transferred from the photoresist to the silicon dioxide mask through etching; and finally, the pattern formed on the silicon dioxide mask is transferred to the wafer through etching to form the required monolithic waveguide structure.

[0059] The monolithic waveguide structure is provided with the following components in sequence: InP substrate 1, InP buffer layer 2, InGaAsP / InP high-fold layer 3, N-side wavelength gradient InGaAsP SCH layer 4, strained InGaAsP quantum well active region 5, P-side wavelength gradient InGaAsP SCH layer 6, and InGaAsP etch cutoff layer 7.

[0060] In the fabrication of monolithic waveguide structures, the InP substrate serves as a crystal growth support, providing structural support for the epitaxial layer.

[0061] InP buffer layers are used to alleviate lattice mismatch between the substrate and the epitaxial layer, thereby improving the growth quality of epitaxial materials;

[0062] InGaAsP / InP high-flush layers are used to reduce the optical confinement factor, ensuring that most of the optical power is effectively amplified in the active region. The high-flush layers also help maintain the stable transmission of the fundamental mode, suppress the generation of higher-order modes, and improve the quality of the output beam.

[0063] The SCH layer of N-side wavelength-gradient InGaAsP and the SCH layer of P-side wavelength-gradient InGaAsP together form a double heterojunction, forming a wavelength-gradient structure to enable band continuity, reduce interface defects, improve hole injection efficiency and MQW carrier uniformity, and further improve carrier transport efficiency.

[0064] The strained InGaAsP quantum well active region employs a structure comprising six quantum wells and five quantum barriers, providing the chip with the required gain while adjusting the quantum well width to achieve the desired wavelength range.

[0065] When the chip adopts an RWG structure, the InGaAsP etching stop layer is used to ensure that the etching depth matches the design value during the etching process.

[0066] When it is necessary to optimize the heat dissipation of the amplifier, the heat dissipation capacity of the amplifier can be increased by thinning the InP substrate. After thinning, the remaining thickness of the InP substrate should be 110-120um.

[0067] The chip has a cavity length ranging from 2500 to 2620 μm and a width ranging from 550 to 650 μm.

[0068] like Figure 3 As shown in d, the length of the straight waveguide region of the first waveguide ranges from 160 to 170 μm; the length of the higher-order continuously varying ridge width gradient adiabatic waveguide region of the second waveguide ranges from 2300 to 2400 μm; and the length of the straight waveguide region of the third waveguide ranges from 40 to 50 μm.

[0069] The ridge width of the straight waveguide region 10 of the third waveguide is 9~10um, so that the first and third waveguides can slowly convert the mode field size of the optical fiber or input waveguide to the size that best matches the active region of SOA, thereby increasing the optical power density of the nonlinear interaction region, improving the efficiency of nonlinear effects, and effectively preventing the deviation between the actual waveguide and the design value caused by cleavage error, which affects the output power and coupling efficiency.

[0070] The height range of the first, second, and third waveguides is 2.2~2.5µm.

[0071] The widths of the first and third waveguides are the same as the width of the input optical end of the second waveguide, and the curvatures at their connection points are the same.

[0072] The combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure with a tilt angle of 6 to 7 degrees. The narrow ridge end of the monolithic waveguide structure is the light input end 11, and the wide ridge end is the light output end 12.

[0073] In this embodiment, the top-view shape of the integrally formed waveguide structure is an axisymmetric structure that gradually widens from narrow. The high-order continuous thermally insulating waveguide can compensate for aberrations, improve mode purity, and further improve fiber coupling efficiency.

[0074] In this embodiment, the ridge width of the straight waveguide region 10 of the third waveguide is 9~10um. The first and third waveguides can slowly convert the mode field size of the optical fiber or input waveguide into the size that best matches the active region of the SOA, thereby increasing the optical power density of the nonlinear interaction region, improving the efficiency of nonlinear effects, and effectively preventing the deviation between the actual waveguide and the design value caused by cleavage error, which would affect the output power and coupling efficiency.

[0075] like Figure 4 As shown, Figure 4 For the same epitaxial structure, the same injection power, the same test temperature, and the same test current, the corresponding Figure 2 The test results for the amplification power and coupling efficiency of four waveguide structures are presented. The test results show that the waveguide structure described in this invention combines high amplification power and high coupling efficiency, with an amplification power approaching that of a ridge-width gradient linear waveguide structure, while its coupling efficiency is close to that of a tilted waveguide.

Claims

1. A semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency, characterized in that: The optical amplifier waveguide structure includes a first waveguide (8), a second waveguide (9), and a third waveguide (10) arranged in sequence. The first waveguide is a straight waveguide region located at the light input end of the waveguide structure. The third waveguide is a straight waveguide region located at the light output end of the waveguide structure. The second waveguide is an adiabatic waveguide region with a ridge width that varies as a high-order continuous function. In the direction of light propagation, the width of the adiabatic waveguide region increases from narrow to wide. The curvature at the beginning / end of the adiabatic waveguide region is the same as the curvature of the straight waveguide region before and after the adiabatic waveguide region. The ridge width of the adiabatic waveguide region gradually changes. The waveguide width at the beginning / end of the adiabatic waveguide region is the same as the width of the straight waveguide region before and after the adiabatic waveguide region.

2. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 1, characterized in that: When a semiconductor optical amplifier is working, it uses an optical fiber or an input waveguide as the optical input end. The first waveguide and the third waveguide serve as mode conversion components to convert the mode field size of the light injected at the optical input end into the size that best matches the active region of the semiconductor optical amplifier (SOA).

3. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 2, characterized in that: After the injected light enters the waveguide structure, it undergoes stable single-mode amplification at the first waveguide and then power amplification at the second waveguide to reduce the probability of higher-order mode excitation.

4. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 3, characterized in that: The widths of the first and third waveguides are the same as the width of the input optical end of the second waveguide, and the curvatures at their junctions are the same. The second waveguide is a high-order continuous nonlinear adiabatic waveguide. When the second waveguide is used in a chip, the high-order continuous variation of the second waveguide ridge width is expressed as a high-order continuous function. ， In the formula, / Cavity length of the chip, In the formula, the higher-order continuous function is used to define the variation trend of the second waveguide ridge width, which is the waveguide edge curve. The second waveguide is an axisymmetric structure whose width gradually increases in the optical transmission direction. It is used to compensate for aberrations and improve mode purity, thereby further improving the fiber coupling efficiency of the semiconductor optical amplifier.

5. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 4, characterized in that: When designing the waveguide structure, the first waveguide and the third waveguide are used to prevent calculation errors, so as to avoid deviation between the actual waveguide and the design value.

6. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 4, characterized in that: In the optical amplifier, the combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure. The fabrication process of the monolithic waveguide structure is as follows: first, a top-view pattern of the ridge waveguide pattern is designed; then, a photomask is drawn according to the designed ridge waveguide pattern; then, the waveguide pattern is transferred from the photomask to the photoresist through photolithography; then, the pattern is transferred from the photoresist to the silicon dioxide mask through etching; and finally, the pattern formed on the silicon dioxide mask is transferred to the wafer through etching to form the required monolithic waveguide structure.

7. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 6, characterized in that: The monolithic waveguide structure is provided with the following components in sequence: InP substrate (1), InP buffer layer (2), InGaAsP / InP high-fold layer (3), N-side wavelength gradient InGaAsP SCH layer (4), strained InGaAsP quantum well active region (5), P-side wavelength gradient InGaAsP SCH layer (6), and InGaAsP etch cutoff layer (7).

8. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 7, characterized in that: In the fabrication of monolithic waveguide structures, the InP substrate serves as a crystal growth support, providing structural support for the epitaxial layer. InP buffer layers are used to alleviate lattice mismatch between the substrate and the epitaxial layer, thereby improving the growth quality of epitaxial materials; InGaAsP / InP high-refractive-fold layers are used to reduce the light confinement factor; The SCH layer of N-side wavelength-gradient InGaAsP and the SCH layer of P-side wavelength-gradient InGaAsP together form a double heterojunction, forming a wavelength-gradient structure to enable band continuity, reduce interface defects, and improve hole injection efficiency and MQW carrier uniformity. The strained InGaAsP quantum well active region employs a structure comprising six quantum wells and five quantum barriers, and the desired wavelength range is achieved by adjusting the width of the quantum wells.

9. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 7, characterized in that: When the chip adopts an RWG structure, the InGaAsP etching stop layer is used to ensure that the etching depth matches the design value during the etching process. When it is necessary to optimize the heat dissipation of the amplifier, the heat dissipation capacity of the amplifier can be increased by thinning the InP substrate. After thinning, the remaining thickness of the InP substrate should be 110-120um.

10. The semiconductor optical amplifier waveguide structure with high amplification power and high coupling efficiency according to claim 4, characterized in that: The chip has a cavity length ranging from 2500 to 2620 μm and a width ranging from 550 to 650 μm. The length of the straight waveguide region of the first waveguide ranges from 160 to 170 μm; the length of the higher-order continuously varying ridge width gradient adiabatic waveguide region of the second waveguide ranges from 2300 to 2400 μm; and the length of the straight waveguide region of the third waveguide ranges from 40 to 50 μm. The ridge width of the straight waveguide region 10 in the third waveguide is 9~10µm; The height range of the first, second, and third waveguides is 2.2~2.5µm; The combination of the first waveguide, the second waveguide, and the third waveguide is a monolithic waveguide structure, and the waveguide tilt angle is 6~7°. The narrow ridge end of the monolithic waveguide structure is the light input end (11), and the wide ridge end is the light output end (12).

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