Semiconductor optical amplifier and fabricating method for semiconductor optical amplifier

Abstract

A semiconductor optical amplifier and a fabricating method for a semiconductor optical amplifier. The semiconductor optical amplifier comprises, from bottom to top, an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding layer, a first separated confinement heterostructure (SCH) layer, an active region, a second SCH layer, a first P-type cladding layer, a first P-type contact layer, and a P-type electrode, wherein the thickness of the first passive waveguide layer is less than 1 micron, and the width of the first passive waveguide layer is less than the width of the N-type substrate. By optimizing the thickness of the passive waveguide to regulate the optical confinement factor, a semiconductor optical amplifier having watt-level high saturation output power is achieved.

Description

Semiconductor optical amplifier and its fabrication method

[0001] This application claims priority to Chinese Patent Application No. 202510058110.1, filed on January 13, 2025, entitled "Semiconductor Optical Amplifier and Method for Preparing a Semiconductor Optical Amplifier", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optical communication, and more particularly to a semiconductor optical amplifier and a method for fabricating the semiconductor optical amplifier. Background Technology

[0003] Semiconductor optical amplifiers (SOAs) are important optoelectronic devices widely used in optical communication and signal processing. Compared to fiber optic amplifiers, SOAs offer significant advantages. First, SOAs are small and lightweight, making them suitable for space-constrained applications. Second, SOAs have higher electro-optical conversion efficiency, effectively reducing energy consumption. Furthermore, SOAs possess a wider spectral bandwidth, reaching the 100-nanometer (nm) level, and a broader operating wavelength, covering the ultraviolet to mid-infrared range. Most importantly, SOAs can be integrated on-chip with components such as semiconductor lasers, modulators, and detectors, which not only reduces system costs but also significantly improves the integration and reliability of optoelectronic systems.

[0004] However, SOA still faces technical challenges in terms of output power and coupling efficiency. The output power of SOA is typically no more than 100 milliwatts, which limits high-power applications. In addition, for traditional SOA structures, the optical modes of the waveguide structure and the optical modes of the optical fiber are severely mismatched, resulting in very low coupling efficiency between the traditional SOA and the optical fiber. This severely restricts the maximum fiber output power and noise figure of the device.

[0005] A type of SOA with a planar coupled waveguide structure can improve the output power of the SOA and the coupling efficiency between the SOA and the optical fiber. However, the fabrication of this SOA is difficult. Therefore, how to reduce the fabrication difficulty of the semiconductor optical amplifier while improving the output power of the SOA and the coupling efficiency between the SOA and the optical fiber has become an urgent problem to be solved. Summary of the Invention

[0006] This application provides a semiconductor optical amplifier, aiming to reduce the fabrication difficulty of the semiconductor optical amplifier while improving its output power and coupling efficiency with the optical fiber.

[0007] In a first aspect, a semiconductor optical amplifier is provided, comprising, from bottom to top, an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separated confinement heterostructure (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode, wherein the thickness of the first passive waveguide layer is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate.

[0008] Based on the above technical solution, a first passive waveguide layer exists on the N-type substrate in the semiconductor optical amplifier. This first passive waveguide layer can pull the optical field downwards to the first passive waveguide layer, thereby reducing the overlap between the optical field and the active region, effectively reducing the transmission loss of the optical field. At the same time, reducing the optical field confinement factor in the active region can improve the output power of the semiconductor optical amplifier. Furthermore, by fabricating the first passive waveguide layer, a coupled waveguide structure can be formed, achieving efficient coupling with optical fiber. In addition, the thickness of the first passive waveguide layer in the semiconductor optical amplifier is less than 1 micrometer, thereby reducing the fabrication difficulty of the semiconductor optical amplifier.

[0009] The aforementioned semiconductor optical amplifier integrates a passive waveguide to realize a coupled waveguide system. Optical connections are achieved with other types of optoelectronic devices through the passive waveguide, thereby achieving monolithic integration and large-scale integrated photonic circuits.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the first passive waveguide layer and the N-type cladding constitute a first waveguide structure, and the waveguide type of the first waveguide structure is a buried waveguide.

[0011] Based on the above technical solutions, buried waveguides can surround the waveguide core with low refractive index materials, which can simultaneously confine the optical field in both vertical and horizontal directions, have good mode confinement capabilities, and are suitable for high-density integration.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the first P-type cladding and the first P-type contact layer constitute a second waveguide structure of the active region, and the waveguide type of the second waveguide structure includes any one of the following: ridge waveguide, strip waveguide, or buried waveguide.

[0013] Based on the above technical solutions, the waveguide structure in the active region can be a ridge waveguide, a strip waveguide, or a buried waveguide structure. Different waveguide structures have their own advantages and disadvantages and are suitable for different application scenarios. Different waveguide types can be adopted according to the application scenario requirements.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the thickness of the first passive waveguide layer is less than 1 micrometer, including: the thickness of the first passive waveguide layer is greater than or equal to 400 nanometers and less than or equal to 500 nanometers.

[0015] Based on the above technical solution, the thickness of the first passive waveguide layer can be designed to be between 400 nanometers and 500 nanometers, thereby improving the output power of the semiconductor optical amplifier.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the first refractive index corresponding to the first passive waveguide layer is greater than the second refractive index corresponding to the N-type cladding.

[0017] Based on the above technical solution, the refractive index of the first passive waveguide layer in the semiconductor optical amplifier is greater than the refractive index of the N-type cladding in the semiconductor optical amplifier, so that the optical modes of the active layer in the semiconductor optical amplifier are drawn into the first passive waveguide layer, and some optical modes can be confined in the active region to provide gain.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the material used for the first passive waveguide layer includes indium gallium arsenide phosphide (InGaAsP) or aluminum gallium indium arsenide (AlGaInAs).

[0019] Based on the above technical solution, the material used for the first passive waveguide layer can be InGaAsP or AlGaInAs, which can guide optical signals and help control the optical field.

[0020] In conjunction with the first aspect, in some implementations of the first aspect, the active region is made of any one of the following materials: AlGaInAs, InGaAsP, or quantum dots.

[0021] Based on the above technical solutions, the active region of the semiconductor optical amplifier can be made of materials such as AlGaInAs, InGaAsP, or quantum dots. Different materials are suitable for different application scenarios. The semiconductor optical amplifier can be used in a variety of material systems, is suitable for different active layer gain material systems, has wide applicability, and good process compatibility.

[0022] In conjunction with the first aspect, in some implementations of the first aspect, the semiconductor optical amplifier further includes a buffer layer located between the N-type substrate and the first passive waveguide layer.

[0023] Based on the above technical solution, a buffer layer can be included in the semiconductor optical amplifier. This buffer layer can cover some defects on the N-type substrate, so that the first passive waveguide layer grown subsequently can perform better.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the active region is a multi-quantum-well active region.

[0025] Based on the above technical solution, the active region in a semiconductor optical amplifier can be a multi-quantum-well active region. A multi-quantum-well refers to a system in which multiple quantum wells are combined together. The coupling between the potential wells is strong, and they can form a microstrip.

[0026] In a second aspect, an optical fiber communication system is provided, which includes the semiconductor optical amplifier, laser, and photoelectric PD detector described in the first aspect above, wherein the laser is used to load an optical signal onto a radio frequency (RF) input signal, the optical signal is transmitted through an optical fiber to the semiconductor optical amplifier, and the optical signal is amplified by the semiconductor optical amplifier and then transmitted to the PD detector.

[0027] Thirdly, a communication device is provided, which includes the semiconductor optical amplifier described in the first aspect. Optionally, the communication device may be a base station; or, the communication device may be a remote radio unit (RRU) or an active antenna unit (AAU) in a base station; or, the communication device may be an open radio access network (O-RAN) device; or, the communication device may be an open radio unit (O-RU) in an O-RAN device, etc.

[0028] Fourthly, a method for fabricating a semiconductor optical amplifier is provided. The semiconductor optical amplifier, from bottom to top, comprises an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separation-confined heterojunction (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode. The fabrication method includes:

[0029] A second passive waveguide layer is grown on the N-type substrate; a hard mask material is deposited on a first portion of the second passive waveguide layer, and the hard mask material is patterned to form a hard mask layer; the hard mask layer is etched to remove the portion of the second passive waveguide layer other than the first portion, to obtain the first passive waveguide layer.

[0030] Fifthly, a method for fabricating a semiconductor optical amplifier is provided. The semiconductor optical amplifier, from bottom to top, comprises an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separation-confined heterojunction (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode. The fabrication method includes:

[0031] A hard mask material is deposited on the N-type substrate, and the hard mask material is patterned to form a hard mask layer; the hard mask layer is etched to remove a portion of the hard mask layer; the first passive waveguide layer is grown on the portion corresponding to the portion of the hard mask layer on the N-type substrate.

[0032] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the fabrication method further includes: epitaxial growth on the sidewall of the first passive waveguide layer to obtain the N-type cladding, and removing the hard mask layer; sequentially growing the first SCH layer, the active region, the second SCH layer, the second P-type cladding, and the second P-type contact layer on the N-type cladding; etching the second P-type cladding and the second P-type contact layer to remove portions of the second P-type cladding and the second P-type contact layer to obtain the first P-type cladding and the first P-type contact layer; depositing a metal thin film on the first P-type contact layer, patterning the metal thin film to form the P-type electrode; and depositing an N-type electrode material at the bottom of the N-type substrate layer to obtain the N-type electrode.

[0033] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the thickness of the first passive waveguide layer is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate.

[0034] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the first passive waveguide layer and the N-type cladding constitute a first waveguide structure, and the waveguide type of the first waveguide structure is a buried waveguide.

[0035] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the first P-type cladding and the first P-type contact layer constitute a second waveguide structure of the active region, and the waveguide type of the second waveguide structure includes any one of the following: ridge waveguide, strip waveguide, or buried waveguide.

[0036] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the thickness of the first passive waveguide layer is less than 1 micrometer, including: the thickness of the first passive waveguide layer is greater than or equal to 400 nanometers and less than or equal to 500 nanometers.

[0037] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the first refractive index corresponding to the first passive waveguide layer is greater than the second refractive index corresponding to the N-type cladding.

[0038] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the material used for the first passive waveguide layer includes indium gallium arsenide phosphide (InGaAsP) or aluminum gallium indium arsenide (AlGaInAs).

[0039] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the active region is made of any of the following materials: AlGaInAs, InGaAsP, or quantum dots.

[0040] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the growth of the second passive waveguide layer on the N-type substrate layer includes: growing a buffer layer on the N-type substrate layer, and growing the second passive waveguide layer on the buffer layer.

[0041] In conjunction with the fourth or fifth aspect, in some implementations of the fourth or fifth aspect, the active region is a multi-quantum-well active region.

[0042] In a sixth aspect, a computer-readable storage medium is provided, on which a computer program or instructions are stored, which, when executed on a computer, cause the computer to perform the preparation method described in the fourth or fifth aspect above.

[0043] In a seventh aspect, a chip system is provided, comprising: at least one processor for calling and running a computer program from a memory, causing a communication device equipped with the chip system to perform the preparation method described in the fourth or fifth aspect above.

[0044] Eighthly, a computer program product is provided, which, when run on a computer, causes the computer to perform the preparation method described in the fourth or fifth aspect above.

[0045] The technical effects achieved by the second to eighth aspects mentioned above are similar to those achieved by the corresponding technical means in the first aspect, and will not be repeated here. Attached Figure Description

[0046] Figure 1 shows a system in which the semiconductor optical amplifier provided in this application can be applied.

[0047] Figure 2 is a schematic diagram of a planar coupled waveguide device structure.

[0048] Figure 3 is a schematic diagram showing the relationship between the thickness of a passive waveguide layer and the optical confinement factor.

[0049] Figure 4(a) to (d) are schematic diagrams showing the relationship between the thickness of a passive waveguide layer and the lateral dimensions of the optical mode field.

[0050] Figure 5 is a schematic diagram of the optical field traction of a passive waveguide layer.

[0051] Figure 6 is a simulation diagram of an optical mode field.

[0052] Figure 7 is a schematic structural diagram of a semiconductor optical amplifier provided in this application.

[0053] Figure 8 is a cross-sectional view of a semiconductor optical amplifier provided in this application.

[0054] Figure 9 is another cross-sectional view of a semiconductor optical amplifier provided in this application.

[0055] Figure 10 is a schematic diagram of the effect of the passive waveguide layer thickness on the optical confinement factor of a semiconductor optical amplifier provided in this application.

[0056] Figure 11 is a schematic diagram of the light field of a semiconductor optical amplifier provided in this application.

[0057] Figure 12 is a schematic diagram of the waveguide type provided in this application.

[0058] Figure 13 is a schematic diagram illustrating the effect of different materials provided in this application on the performance of semiconductor optical amplifiers.

[0059] Figure 14 is a schematic structural diagram of another semiconductor optical amplifier provided in this application.

[0060] Figure 15 is a schematic flowchart of a semiconductor optical amplifier fabrication method provided in this application.

[0061] Figure 16 is a schematic diagram of a first passive waveguide grown according to this application.

[0062] Figure 17 is a schematic diagram of another method for growing a first passive waveguide according to this application.

[0063] Figure 18 is a schematic diagram of the growth of each layer of another semiconductor optical amplifier provided in this application. Detailed Implementation

[0064] To facilitate understanding of the embodiments of this application, the following points will be explained first.

[0065] First, in this application, "at least one" refers to one or more, and "more than one" refers to two or more (including two). Furthermore, in the embodiments of this application, "first," "second," and various numerical designations (e.g., "#1," "#2," etc.) are merely distinctions for ease of description and are not intended to limit the scope of the embodiments of this application. The sequence numbers of the processes below do not imply an order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. It should be understood that the objects described in this way can be interchanged where appropriate to describe solutions other than those in the embodiments of this application.

[0066] Second, in the embodiments of this application, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0067] Third, in the embodiments of this application, the terms "of", "corresponding (relevant)", "corresponding", and "associate" can sometimes be used interchangeably. It should be noted that when their differences are not emphasized, their intended meanings are consistent.

[0068] Fourth, in the embodiments of this application, "under the circumstances", "when", and "if" can sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0069] Fifth, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0070] Sixth, in the embodiments shown below, the various optical elements are connected by optical fibers. Specifically, the input or output pigtails of each element and the transmission optical fiber together form a section of optical fiber, which is used for the transmission of signal light between the elements.

[0071] Seventh, in the embodiments shown below, a module can also be understood as an element. For example, an optical amplifier module can also refer to an optical amplifier element, etc.

[0072] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0073] The semiconductor optical amplifier and optical amplification system provided in this application have important applications in wireless base stations, long-range lidar, optical communication networks, and optical sensing, and can enhance signal strength, extend transmission distance, and maintain signal integrity. Furthermore, the semiconductor optical amplifier provided in this application enables monolithic integration of semiconductor optical amplifiers, realizing large-scale photonic integrated circuits, thereby promoting the integration and miniaturization of devices in high-density optical networks and meeting the needs of modern high-speed data transmission and precision signal processing.

[0074] To facilitate understanding, the system in which the semiconductor optical amplifier provided in this application can be applied is briefly introduced below with reference to Figure 1. As shown in Figure 1, the system includes a laser, a semiconductor optical amplifier (SOA), and a photoelectric detector (PD), where the photoelectric detector can be simply referred to as a detector or PD detector.

[0075] Specifically, the laser is responsible for loading the radio frequency (RF) input signal into an optical signal, which is then transmitted through an optical fiber. The optical signal within the fiber is amplified by a semiconductor optical amplifier before reaching a detector. The detector converts the information in the optical signal into an electrical signal, which is then transmitted through an antenna. By using a semiconductor optical amplifier to amplify the optical signal, it is possible to transmit the signal over greater distances or for the detector to receive and convert it into a stronger RF signal.

[0076] It should be understood that Figure 1 is merely an example illustrating the system in which the semiconductor optical amplifier provided in this application can be applied, and does not constitute any limitation on the scope of protection of this application. The semiconductor optical amplifier can also be applied in other scenarios. For example, the system shown in Figure 1 may also include other devices or modules, which will not be listed here.

[0077] To facilitate understanding of the technical solutions of the embodiments of this application, some terms or concepts that may be involved in the embodiments of this application will be briefly described first.

[0078] 1. Optical Array (SOA): An important optoelectronic device widely used in optical communication and signal processing. Compared to fiber optic amplifiers, semiconductor optical amplifiers have significant advantages. First, SOAs are small and lightweight, making them suitable for space-constrained applications. Second, SOAs have higher electro-optical conversion efficiency, effectively reducing energy consumption. Furthermore, SOAs possess a wider spectral bandwidth, reaching the 100-nanometer (nm) level, and a broader operating wavelength, covering the ultraviolet to mid-infrared bands. Most importantly, SOAs can be integrated on-chip with components such as semiconductor lasers, modulators, and detectors, which not only reduces system costs but also significantly improves the integration and reliability of optoelectronic systems.

[0079] However, SOA still faces technical challenges in terms of output power and coupling efficiency. The output power of SOA typically does not exceed 100 milliwatts, which limits high-power applications. Furthermore, for traditional SOA structures, there is a severe mismatch between the optical modes of the waveguide structure and the optical modes of the optical fiber. For example, the refractive index of the waveguide structure may differ from that of the optical fiber; or the shapes of the waveguide structure and the optical fiber may differ. These factors lead to a severe mismatch in the optical modes of the waveguide structure and the optical fiber, resulting in very low coupling efficiency between the SOA and the optical fiber. This significantly restricts the maximum fiber output power and noise figure of the device. Therefore, improving the output power of SOA and its coupling efficiency with optical fiber has become crucial for technological development.

[0080] To improve saturated output power, the key lies in reducing the optical confinement factor of the active region while increasing its thickness or width to create a larger mode size. To improve coupling efficiency, the epitaxial structure and waveguide structure of the SOA need to be optimized to achieve efficient coupling of the SOA with the optical modes of the fiber, while ensuring single-mode operation of the device.

[0081] Small-signal gain and saturated output power are two key performance indicators of SOA. Small-signal gain G0 describes the optical amplification capability of SOA when the signal is sufficiently weak, and can be expressed as: G0=exp[(Γg0-a i )L] (1-1)

[0082] In Equation (1-1), Γ is the optical mode field confinement factor, g0 is the unsaturated gain coefficient of the material, αi is the optical loss coefficient of the device, and L is the physical length of the SOA.

[0083] Saturated output power P sat This refers to the optical output power of the SOA when the gain is reduced to half of the small-signal gain G0, which can be calculated by the following formula:

[0084] In equation (1-2), w and d represent the width and thickness of the active region, respectively, hν is the photon energy, a is the differential gain, and τ is the carrier lifetime. Increasing the thickness of the waveguide layer can effectively reduce Γ, thereby improving P. sat This technology can also reduce the optical loss α of the device by reducing the contact between the optical mode and the sidewall. i .

[0085] 2. Planar Coupled Waveguide: As a possible implementation, during material epitaxial growth, after the N-type substrate layer is grown and before the active layer is grown, a passive waveguide layer is grown to reduce the optical confinement factor of the active region, achieving high saturation output power and forming a planar coupled waveguide structure. This generates a circular fundamental mode spot, enabling efficient coupling with the optical fiber. The structure of the planar coupled waveguide device is shown in Figure 2. From bottom to top, its structure includes an N-side electrode, an N-type substrate layer, a waveguide layer, an active region, a P-type cladding, a P-side ohmic contact layer, and a P-side electrode.

[0086] By controlling the thickness of the waveguide layer, the optical confinement factor and the shape of the optical mode can be tuned, thereby achieving high saturation output power and high coupling efficiency.

[0087] On the one hand, as shown in Figure 3, as the thickness of the passive waveguide layer gradually increases, the optical confinement factor also decreases, thereby achieving high saturation output power.

[0088] On the other hand, as shown in Figures 4(a) to (d), as the thickness of the passive waveguide layer gradually increases, the lateral dimension of the optical mode field gradually increases. By controlling the thickness of the waveguide layer, a circular output spot can be achieved, which is beneficial to achieving efficient coupling between SOA and optical fiber.

[0089] As another possible implementation, after completing the growth of the N-type contact layer and before proceeding to the growth of the active layer, a passive waveguide layer is first grown, as shown by the arrow in Figure 5. The function of this layer is to draw the optical field downwards to the waveguide layer, thereby reducing the overlap between the optical field and the active region. This design effectively reduces the transmission loss of the optical field. i This optimization also reduced the optical field confinement factor Γ. Through this optimization, not only was a larger gain achieved, but the saturated output optical power was also significantly improved.

[0090] As shown in Figure 6, after adding a passive waveguide layer, it can be clearly seen that the waveguide layer successfully pulls a portion of the optical field, reducing the overlap between the optical field and the active region. This phenomenon indicates that the optical confinement factor is indeed reduced, thereby optimizing the optical field distribution and improving the saturated output power.

[0091] The preceding text, with reference to Figure 1, briefly introduced the systems to which the sensing method provided in the embodiments of this application can be applied, and introduced the basic concepts that may be involved in the embodiments of this application, including SOA and planar coupled waveguide structures. It should be understood that the application scenarios shown in Figure 1 are merely examples and do not constitute any limitation on the scope of protection of this application. For example, the SOA provided in this application can be applied not only to optical communication systems, but also to non-communication systems, such as lidar, laser sensing, or laser imaging. Further examples will not be provided here.

[0092] It should be noted that traditional SOA waveguides have limited performance in terms of saturated output power, typically not exceeding 100 milliwatts, which is insufficient to meet the demands of high-power applications and restricts their widespread use. Furthermore, the optical modes of traditional SOA waveguides are severely mismatched with those of optical fibers, resulting in very low coupling efficiency. This significantly limits the maximum fiber output power and noise figure of the device.

[0093] The aforementioned planar coupled waveguide structure requires a passive waveguide structure 3-5 micrometers thick, making the growth of SOA epitaxial structures extremely difficult. Furthermore, due to the significant thickness of the passive waveguide, it is incompatible with other on-chip device processes, hindering waveguide coupling and making monolithic integration challenging. Additionally, the SOA epitaxial structure shown in Figure 5 includes a single, continuous passive waveguide layer, making it impossible to control the SOA mode field and achieve efficient direct coupling between the SOA and the optical fiber. Moreover, the passive waveguide layer lacks lateral optical confinement, preventing monolithic integration and hindering integration and efficient coupling with other optical components.

[0094] To address the problems existing in the aforementioned SOA structure, this application provides an SOA structure aimed at improving the output power of the SOA and the coupling efficiency between the SOA and the optical fiber.

[0095] Figure 7 is a schematic structural diagram of a semiconductor optical amplifier 100 provided in this application. As shown in Figure 7, the semiconductor optical amplifier includes, from bottom to top, an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first SCH layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode.

[0096] Specifically, in this application, the thickness of the first passive waveguide layer in the semiconductor optical amplifier is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate.

[0097] For example, the uses of the various functional layers included in the semiconductor optical amplifier of this application can be simply described as follows:

[0098] For example, the P-type electrode layer in a semiconductor optical amplifier is used to provide a path for current injection into the semiconductor optical amplifier;

[0099] For example, the N-type electrode layer in a semiconductor optical amplifier is used to form a complete electrode contact structure;

[0100] For example, the SCH layer (e.g., the first SCH layer and the second SCH layer) in a semiconductor optical amplifier is used to confine carriers and photons in the active layer and the waveguide layer, respectively.

[0101] For example, the first passive waveguide layer in a semiconductor optical amplifier is used to pull the optical field downward to the first passive waveguide layer, thereby reducing the overlap between the optical field and the active region and effectively reducing the transmission loss of the optical field.

[0102] For example, cladding in a semiconductor optical amplifier (such as an N-type cladding and a first P-type cladding) is used to ensure further confinement and conduction of the optical field, enhancing the optical effect of the waveguide structure;

[0103] For example, the active region (or active layer) in a semiconductor optical amplifier is used to achieve optical amplification;

[0104] For example, the first P-type contact layer in a semiconductor optical amplifier is used to provide a carrier transport channel for subsequent electrode fabrication.

[0105] It should be understood that the functional descriptions of the different functions in the above semiconductor optical amplifier are merely examples and do not constitute any limitation on the scope of protection of this application.

[0106] It should be noted that the various layers included in the semiconductor optical amplifier in this application are functional divisions and are not limited to each functional layer containing only one layer. For example, the N-type electrode may include one or more N-type electrode layers; and for example, the first passive waveguide layer may include one or more first passive waveguide layers, etc.

[0107] Optionally, the width of the first passive waveguide layer is approximately equal to the width of the waveguide structure in the active region. The waveguide structure in the active region consists of a first P-type cladding and a first P-type contact layer. For example, the width of the first passive waveguide layer is equal to the width of the first P-type cladding.

[0108] Optionally, the distance between the first passive waveguide layer and the active region is within a certain range to improve the saturated output power of the semiconductor optical amplifier. For example, the distance between the first passive waveguide layer and the active region can be represented by L, as shown in Figure 7. The value of L can be greater than or equal to 1.5 micrometers and less than or equal to 3 micrometers.

[0109] It should be noted that Figure 7 shows a front view of the semiconductor optical amplifier. Additionally, Figure 8 is a cross-sectional view of the semiconductor optical amplifier.

[0110] For example, the width of the first passive waveguide layer being smaller than the width of the N-type substrate can be described as follows: the width of the first passive waveguide layer is width #1, and the width of the N-type substrate is width #2, wherein width #1 is smaller than width #2. For example, as shown in Figure 9, the first passive waveguide layer is not a complete passive waveguide layer on the N-type substrate; the first passive waveguide layer only covers a portion of the N-type substrate.

[0111] The aforementioned first passive waveguide layer is used to pull the optical field in the active region downward, reducing the overlap between the optical field and the first P-type cladding, reducing the optical field transmission loss, and at the same time reducing the optical field confinement factor in the active region, enabling the semiconductor optical amplifier provided in this application to achieve a larger gain while improving the saturated output power.

[0112] For example, in this application, the optical modes confined to the active layer are pulled into the passive waveguide by the first passive waveguide layer. However, the first passive waveguide layer cannot be too thick (for example, the thickness of the first passive waveguide layer in this application is less than 1 micrometer), so that some optical modes can be confined to the active region to provide gain. The N-type cladding above the first passive waveguide layer can be designed to be thicker than the first threshold, so that the first passive waveguide layer, the N-type cladding and the active layer can together form a large-mode-size optical waveguide structure.

[0113] By way of example and not limitation, the thickness of the first passive waveguide layer is less than 1 micrometer, and can be greater than or equal to 400 nanometers and less than or equal to 500 nanometers. As shown in Figure 10, it can be seen that the optical confinement factor of the semiconductor optical amplifier decreases as the thickness of the first passive waveguide layer increases. Optionally, the thickness of the first passive waveguide layer can be between 400-500 nm to reduce the optical confinement factor of the semiconductor optical amplifier and improve its output power.

[0114] As shown in Figure 11, after adding a passive waveguide layer, it can be clearly seen that the waveguide layer successfully pulls a portion of the optical field, reducing the overlap between the optical field and the active region. This phenomenon indicates that the optical confinement factor is indeed reduced, thereby optimizing the optical field distribution and improving the saturated output power. Furthermore, as can be seen from Figure 11, the semiconductor optical amplifier in this application can achieve a coupled waveguide system by optimizing the epitaxial structure. For example, the thickness of the first passive waveguide layer in the aforementioned semiconductor optical amplifier is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate in the semiconductor optical amplifier. In this case, the optical mode spot of the semiconductor optical amplifier can be adjusted to be circular or nearly circular, and the mode spot diameter is close to the mode spot diameter of a single-mode fiber, thereby improving the coupling efficiency between the semiconductor optical amplifier and the optical fiber and solving the problem of difficult efficient coupling between conventional semiconductor optical amplifiers and optical fibers.

[0115] For example, the first passive waveguide layer and the N-type cladding constitute a first waveguide structure, and the waveguide type of the first waveguide structure is a buried waveguide.

[0116] For example, the first P-type cladding and the first P-type contact layer constitute the second waveguide structure of the active region, and the waveguide type of the second waveguide structure includes any one of the following: ridge waveguide, strip waveguide, or buried waveguide.

[0117] It should be understood that, based on Maxwell's equations, the waveguide effect is achieved through total internal reflection of light between materials with different refractive indices. Waveguide modes include the fundamental mode and higher-order modes, which determine the propagation characteristics of light. Various waveguides have different mode distributions, losses, and coupling characteristics. Waveguide design must consider losses, coupling efficiency, and fabrication processes to optimize optical transmission efficiency and signal stability. In integrated optics, the main waveguide types include strip waveguides, buried waveguides, and ridge waveguides, as shown in Figure 12.

[0118] Slab waveguide: Composed of two layers of high-refractive-index material and a middle layer of low-refractive-index material, light is confined to a single plane by the upper and lower layers when propagating in the waveguide. Slab waveguides have a simple structure but lack lateral optical constraint.

[0119] Buried waveguide: The waveguide core is surrounded by a low-refractive-index material, which can confine the light field in both vertical and horizontal directions, has good mode confinement capability, and is suitable for high-density integration.

[0120] Ridge waveguide: By etching a ridge-like structure on the waveguide core, the light field is confined in the vertical and horizontal directions, enabling more precise control of the light field, and is suitable for on-chip integration.

[0121] Different waveguide structures have their own advantages and disadvantages and are suitable for different application scenarios. The semiconductor optical amplifier in this application supports different waveguide structures, has wide applicability, and good process compatibility.

[0122] It should be noted that the waveguide types mentioned above are merely examples and do not constitute any limitation on the scope of protection of this application. Waveguide types may also take other forms, which will not be listed here.

[0123] For example, the first refractive index of the first passive waveguide layer is greater than the second refractive index of the N-type cladding. For instance, the material used for the first passive waveguide layer includes indium gallium arsenide phosphide (InGaAsP) or aluminum gallium indium arsenide (AlGaInAs).

[0124] It should be understood that the material used for the first passive waveguide layer can also be other materials besides InGaAsP or AlGaInAs based on InP substrates, such as GaAs, AlGaAs, InGaAs, InGaAsSb, InGaAsP, GaInP, AlGaInP based on GaAs or Ge substrates, or GaN, InGaN, AlGaN, etc. based on GaN or sapphire substrates.

[0125] For example, the active region of the semiconductor optical amplifier described above uses any of the following materials: InGaAs, AlGaInAs, InGaAsP, GaAs, AlGaAs, InGaAs, InGaAs, InGaAsSb, InGaAsP, GaInP, AlGaInP, or GaN, InGaN, AlGaN, etc. based on GaN or sapphire substrate materials, as well as quantum dot light-emitting materials composed of these materials.

[0126] In the semiconductor optical amplifier material system, InGaAsP, AlGaInAs, and quantum dot (QD) materials each have the following advantages and disadvantages:

[0127] InGaAsP: It has a mature manufacturing process and is suitable for various optical communication applications across a wide wavelength range. However, it is sensitive to temperature changes, leading to performance degradation at high temperatures. Furthermore, under high-power operation, InGaAsP devices exhibit low saturation output power, limiting their applicability in high-power applications.

[0128] AlGaInAs contains a group 5 element, facilitating control over growth quality and improving the performance of the emitting region. Its refractive index is higher than that of InGaAsP with the same bandgap, giving InP semiconductor lasers greater electron confinement and superior optical properties. Furthermore, the tensile strain effect between the AlGaInAs quantum well and the InP substrate improves band separation and gain levels, optimizes the valence band structure, reduces Auger recombination rate and valence band absorption, and increases transparent carrier concentration and quantum efficiency, thus significantly improving the temperature characteristics of epitaxial lasers. However, the growth process of AlGaInAs structures is relatively complex and may lead to the formation of local states, thereby affecting carrier dynamics and emission characteristics.

[0129] Quantum dot materials: Quantum dots offer numerous advantages as gain materials, such as low confinement factor, low internal loss, low threshold current density, and fast carrier dynamics. Their fast gain response makes them suitable for amplifying high-speed signals without mode effects; low threshold current density, internal loss, and optical confinement factor collectively contribute to low noise characteristics; and the non-uniformly broadened gain provides broadband amplification capabilities. However, the epitaxial growth process of quantum dots requires precise control over the size, distribution, and density of the quantum dots, leading to a complex and costly manufacturing process. Precise growth of high-quality quantum dots is crucial for achieving high-performance SOA, but it also presents significant technical and economic challenges.

[0130] The different material systems mentioned above each have their own advantages and disadvantages, and are suitable for different application scenarios. As shown in Figure 13, the band structure can be adjusted by changing the material composition, thereby affecting the performance of SOA.

[0131] Optionally, the semiconductor optical amplifier further includes a buffer layer located between the N-type substrate and the first passive waveguide layer. As shown in Figure 14, the surface of the N-type substrate is typically covered with a buffer layer to facilitate the growth of subsequent passive waveguide layers, N-type cladding, etc., on the buffer layer.

[0132] As described above, the semiconductor optical amplifier provided in this application has a first passive waveguide layer on the N-type substrate. This first passive waveguide layer can pull the optical field downwards to the first passive waveguide layer, thereby reducing the overlap between the optical field and the active region, effectively reducing the transmission loss of the optical field. At the same time, reducing the optical field confinement factor in the active region can improve the output power of the semiconductor optical amplifier. Furthermore, by fabricating the first passive waveguide layer, a coupled waveguide structure can be formed, achieving efficient coupling with the optical fiber. In addition, the thickness of the first passive waveguide layer in the semiconductor optical amplifier is less than 1 micrometer, thereby reducing the fabrication difficulty of the semiconductor optical amplifier.

[0133] It should be understood that this application primarily describes the waveguide design in the semiconductor optical amplifier shown in Figure 7 above (e.g., the thickness of the passive waveguide, the shape of the passive waveguide, examples of passive and active waveguides, etc.). It can be understood that this application provides a waveguide structure comprising a passive waveguide layer and an N-type cladding, wherein the thickness of the passive waveguide layer is less than 1 micrometer. This waveguide design can also be applied to devices other than SOA, such as semiconductor lasers, detectors, or modulators, and other devices requiring the design and fabrication of optical waveguide structures, which will not be illustrated here.

[0134] This application also provides a method for fabricating a semiconductor optical amplifier. For ease of understanding, the method for fabricating the semiconductor optical amplifier provided in this application is briefly described below with reference to Figure 15.

[0135] Figure 15 is a schematic flowchart of a semiconductor optical amplifier fabrication method provided in this application. It includes the following steps:

[0136] S1510, the first passive waveguide layer is grown on an N-type substrate.

[0137] By way of example and not limitation, the process of fabricating a semiconductor optical amplifier in this application, including but not limited to the following two methods, involves growing a first passive waveguide layer on an N-type substrate:

[0138] Method 1: Growing the first passive waveguide layer on an N-type substrate includes the following steps:

[0139] Step 1.1: A second passive waveguide layer is grown on an N-type substrate. For example, the second passive waveguide layer is grown on a semiconductor N-type substrate such as indium phosphide (InP), and the second passive waveguide layer is generally made of a material such as InGaAsP. Optionally, a buffer layer may be grown between the N-type substrate and the second passive waveguide layer.

[0140] Step 1.2: Deposit a layer of hard mask material on a first portion of the second passive waveguide layer, and pattern the hard mask material to form a hard mask layer. For example, deposit a layer of hard mask material (e.g., silicon dioxide (SiO2) or silicon nitride (SiNx)) on the second passive waveguide layer using photolithography and pattern it for use in the subsequent etching step.

[0141] Step 1.3: Use a hard mask layer to etch away the portion of the second passive waveguide layer other than the first portion, to obtain the first passive waveguide layer. For example, anisotropic etching can be performed using a mask layer to precisely remove a portion of the material of the second passive waveguide layer, forming the desired first passive waveguide layer. The desired lateral and longitudinal geometric dimensions of the waveguide can be achieved through etching.

[0142] Furthermore, after forming the required first passive waveguide layer, the initially deposited hard mask layer can be removed.

[0143] To facilitate understanding, Figure 16 details the process of growing the first passive waveguide layer on an N-type substrate as shown in Method 1. As shown in Figure 16, a buffer layer is grown on an indium phosphide semiconductor substrate, and then a passive waveguide layer is grown on the buffer layer. A hard mask material is deposited using photolithography to pattern it for use in the etching step. Anisotropic etching is then performed using the mask layer to remove a portion of the passive waveguide layer material, forming the desired waveguide structure.

[0144] Method 2: Growing the first passive waveguide layer on an N-type substrate includes the following steps:

[0145] Step 2.1: A hard mask material is deposited on an N-type substrate and patterned to form a hard mask layer. For example, a hard mask material is deposited on a semiconductor N-type substrate such as indium phosphide (InP) and patterned to form a hard mask layer.

[0146] Step 2.2: Etch the hard mask layer to remove a portion of it.

[0147] Step 2.3: The first passive waveguide layer is grown on a portion corresponding to a part of the N-type substrate hard mask layer. For example, the first passive waveguide layer is grown on a semiconductor N-type substrate such as indium phosphide (InP), and the first passive waveguide layer generally uses materials such as InGaAsP.

[0148] Furthermore, after forming the required first passive waveguide layer, the initially deposited hard mask layer can be removed.

[0149] To facilitate understanding, the process of growing the first passive waveguide layer on an N-type substrate in the case shown in Method 2 is described in detail with reference to Figure 17. As shown in Figure 17, a hard mask material is deposited on an indium phosphide (InP) semiconductor substrate using photolithography and patterned for the etching step. Anisotropic etching is performed using the mask layer to precisely remove a portion of the hard mask layer material. After removing the portion of the hard mask layer material, a passive waveguide layer is grown in the removed area to form the desired waveguide structure.

[0150] Furthermore, after the growth of the first passive waveguide layer is completed, other layers of the semiconductor optical amplifier can be grown. Exemplarily, the fabrication method shown in Figure 15 further includes:

[0151] S1520, growing N-type cladding.

[0152] Specifically, an N-type cladding is obtained by epitaxial growth on the sidewall of the first passive waveguide layer. Optionally, if the first passive waveguide layer is obtained by growing it in the manner described above (method 1), the initially deposited hard mask layer can be removed after the N-type cladding is grown, and the remaining mask material can be cleaned up to prepare for subsequent epitaxial growth steps.

[0153] S1530, grows a first SCH layer, an active region, a second SCH layer, a second P-type cladding layer, and a second P-type contact layer.

[0154] Specifically, a first SCH layer, an active region, a second SCH layer, a second P-type cladding layer, and a second P-type contact layer are sequentially grown on the N-type cladding layer. For example, the second P-type contact layer can be grown epitaxially on the second P-type cladding layer (e.g., P-type InP) to provide a carrier transport channel for subsequent electrode fabrication.

[0155] S1540, etching to obtain the first P-type cladding layer and the first P-type contact layer.

[0156] Specifically, etching is performed on the second P-type cladding and the second P-type contact layer to remove portions of the second P-type cladding and the second P-type contact layer, resulting in the first P-type cladding and the first P-type contact layer. Etching on the second P-type cladding and the second P-type contact layer allows for the etching of the active waveguide structure, which is responsible for optical amplification.

[0157] S1550, for growing P-type and N-type electrodes.

[0158] Specifically, a metal thin film is deposited on the first P-type contact layer, and the metal thin film is patterned to form a P-type electrode. For example, a metal thin film (such as AuZn) is deposited through a metallization process, and the P-type electrode is patterned using photolithography and etching techniques to provide a path for current injection into the device.

[0159] Specifically, an N-type electrode material is deposited at the bottom of an N-type substrate to obtain an N-type electrode. For example, in the bottom of a semiconductor optical amplifier, an N-type electrode material (such as AuGeNi) is deposited and etched to form a complete electrode contact structure.

[0160] To facilitate understanding, Figure 18 provides a detailed schematic diagram of the growth of other layers after the first passive waveguide layer is grown on the N-type substrate.

[0161] It should be understood that the method for fabricating the semiconductor optical amplifier shown in Figure 15 is merely an example and does not constitute any limitation on the scope of protection of this application. The semiconductor optical amplifier structure shown in Figure 7 can also be realized by other fabrication methods, which will not be elaborated in this application.

[0162] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0163] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0164] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0165] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0166] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0167] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0168] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A semiconductor optical amplifier, characterized in that, The semiconductor optical amplifier comprises, from bottom to top, an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separation-confined heterojunction (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode. The thickness of the first passive waveguide layer is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate.

2. The semiconductor optical amplifier according to claim 1, characterized in that, The first passive waveguide layer and the N-type cladding constitute a first waveguide structure, and the waveguide type of the first waveguide structure is a buried waveguide.

3. The semiconductor optical amplifier according to claim 1 or 2, characterized in that, The first P-type cladding and the first P-type contact layer constitute the second waveguide structure of the active region, and the waveguide type of the second waveguide structure includes any one of the following: Ridge waveguide, strip waveguide, or buried waveguide.

4. The semiconductor optical amplifier according to any one of claims 1 to 3, characterized in that, The thickness of the first passive waveguide layer is less than 1 micrometer, comprising: The thickness of the first passive waveguide layer is greater than or equal to 400 nanometers and less than or equal to 500 nanometers.

5. The semiconductor optical amplifier according to any one of claims 1 to 4, characterized in that, The first refractive index of the first passive waveguide layer is greater than the second refractive index of the N-type cladding layer.

6. The semiconductor optical amplifier according to any one of claims 1 to 5, characterized in that, The first passive waveguide layer is made of materials including indium gallium arsenide phosphide (InGaAsP) or aluminum gallium indium arsenide (AlGaInAs).

7. The semiconductor optical amplifier according to any one of claims 1 to 6, characterized in that, The active region is made of any of the following materials: AlGaInAs, InGaAsP, or quantum dots.

8. The semiconductor optical amplifier according to any one of claims 1 to 7, characterized in that, The semiconductor optical amplifier further includes a buffer layer located between the N-type substrate and the first passive waveguide layer.

9. The semiconductor optical amplifier according to any one of claims 1 to 8, characterized in that, The active region is a multi-quantum-well active region.

10. An optical fiber communication system, characterized in that, Includes semiconductor optical amplifiers, lasers, and photoelectric PD detectors as described in any one of claims 1 to 9. The laser is used to load the radio frequency (RF) input signal into an optical signal. The optical signal is transmitted through an optical fiber to the semiconductor optical amplifier, and after being amplified by the semiconductor optical amplifier, it is transmitted to the PD detector.

11. A communication device, characterized in that, Includes a semiconductor optical amplifier as described in any one of claims 1 to 9.

12. A method for fabricating a semiconductor optical amplifier, characterized in that, The semiconductor optical amplifier, from bottom to top, includes an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separated confined heterojunction (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode. The fabrication method includes: A second passive waveguide layer is grown on the N-type substrate; A hard mask material is deposited on the first portion of the second passive waveguide layer, and the hard mask material is patterned to form a hard mask layer; The hard mask layer is used to etch away the portion of the second passive waveguide layer other than the first portion, thus obtaining the first passive waveguide layer.

13. A method for fabricating a semiconductor optical amplifier, characterized in that, The semiconductor optical amplifier, from bottom to top, includes an N-type electrode, an N-type substrate, a first passive waveguide layer, an N-type cladding, a first separated confined heterojunction (SCH) layer, an active region, a second SCH layer, a first P-type cladding, a first P-type contact layer, and a P-type electrode. The fabrication method includes: A hard mask material is grown and deposited on the N-type substrate, and the hard mask material is patterned to form a hard mask layer; The hard mask layer is etched to remove a portion of it; The first passive waveguide layer is grown on a portion corresponding to a portion of the hard mask layer on the N-type substrate.

14. The preparation method according to claim 12 or 13, characterized in that, The preparation method further includes: Epitaxial growth is performed on the sidewall of the first passive waveguide layer to obtain the N-type cladding, and the hard mask layer is removed. The first SCH layer, the active region, the second SCH layer, the second P-type cladding layer, and the second P-type contact layer are sequentially grown on the N-type cladding layer. Etching is performed on the second P-type cladding layer and the second P-type contact layer to remove a portion of the second P-type cladding layer and a portion of the second P-type contact layer to obtain the first P-type cladding layer and the first P-type contact layer. A metal thin film is deposited on the first P-type contact layer, and the metal thin film is patterned to form the P-type electrode; An N-type electrode material is deposited on the bottom of the N-type substrate to obtain the N-type electrode.

15. The preparation method according to any one of claims 12 to 14, characterized in that, The thickness of the first passive waveguide layer is less than 1 micrometer, and the width of the first passive waveguide layer is less than the width of the N-type substrate.

16. The preparation method according to claim 15, characterized in that, The thickness of the first passive waveguide layer is less than 1 micrometer, comprising: The thickness of the first passive waveguide layer is greater than or equal to 400 nanometers and less than or equal to 500 nanometers.

17. The preparation method according to claim 12, characterized in that, The process of growing a second passive waveguide layer on the N-type substrate includes: A buffer layer is grown on the N-type substrate, and the second passive waveguide layer is grown on the buffer layer.

18. The preparation method according to any one of claims 12 to 17, characterized in that, The active region is a multi-quantum-well active region.

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