Striped channel planar coupled waveguide semiconductor optical amplifier and preparation method thereof

Abstract

The application discloses a strip channel flat plate coupled waveguide semiconductor optical amplifier and a preparation method thereof, and belongs to the field of semiconductor optical amplifiers. The strip channel waveguide layer with high refractive index is flatly coupled with the active region, and the strip channel waveguide layer and the active region are separated by an N-type isolation layer of low refractive material. By changing the thickness of the N-type isolation layer, the material composition or the thickness of the channel waveguide layer, the optical field confinement factor can be changed in a wide range, and the mode field spot size can be adjusted. By reducing the optical field confinement factor and expanding the mode field spot, the saturation power of the semiconductor optical amplifier can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optical amplifiers, and more specifically to a strip-channel planar coupled waveguide semiconductor optical amplifier and its fabrication method. Background Technology

[0002] Semiconductor optical amplifiers (SAPA) are crucial functional devices in optical networks. They can be used for direct linear amplification of optical signals in their linear region, and for nonlinear functions such as power equalization in their saturation region. Linear amplification of optical signals is the most traditional application of SAPA, specifically categorized as post-amplification at the transmitter, in-circuit amplification, and pre-amplification at the receiver. Erbium-doped fiber amplifiers (EDFAs) are commonly used in-circuit amplifiers, exhibiting excellent performance in terms of saturation power, noise figure, and gain polarization dependence. However, due to limitations in the gain material, EDFAs can only conveniently cover the C-band centered around 1550nm. In contrast, while SAPA performance is inferior to EDFA in terms of saturation power and noise figure, by adjusting the material in the active region, SAPA can cover a wider operating wavelength range. Furthermore, SAPA offers advantages such as small size and ease of integration, leading to a broad range of applications.

[0003] Common semiconductor optical amplifiers include ridge waveguide structures and buried heterojunction structures. Ridge waveguide semiconductor optical amplifiers are the most common structure. The presence of the ridge waveguide confines light laterally and ensures that carriers are injected only into the ridge waveguide, preventing lateral carrier diffusion. This structure is relatively simple to fabricate, requiring no disruption of the active region, and offers advantages such as low cost and high yield. However, due to the presence of the ridge, the contact electrode area is small, resulting in high series resistance. Furthermore, the presence of the ridge reduces stress tolerance, making it inconvenient to mount the device onto the heat sink via eutectic bonding. Under conditions requiring a large bias current, semiconductor optical amplifiers generate significant Joule heat, and the high thermal resistance combined leads to an increase in the active region junction temperature, causing a sharp deterioration in output characteristics at high temperatures.

[0004] The buried heterojunction structure involves removing material from both sides of the optical waveguide to form a pair of parallel channels. The gain region within these channels, along with all the wide-bandgap material on the upper side and a portion of the wide-bandgap material on the lower side, is also removed. A reverse PN junction composed of wide-bandgap semiconductor material is then regrown within the channels. Buried heterojunction optical amplifiers require multiple epitaxial growth processes, resulting in complex fabrication and high costs. Furthermore, the active region needs to be etched, leading to low yield and poor reliability. While this structure can reduce the optical field confinement factor and thus increase saturation power by reducing the thickness of the active region, the optical field in the vertical direction is confined by the high-refractive-index active region and the low-refractive-index cladding on both sides. The peak of the optical field occurs at the active region, and the thickness of the active region cannot be reduced indefinitely. Therefore, the optical field confinement factor of this structure cannot be significantly reduced.

[0005] Since the saturated output power of an optical amplifier is primarily determined by its optical field confinement factor (OPF), and is inversely proportional to the OPF, the aforementioned semiconductor optical amplifiers based on ridge waveguides or buried heterojunction structures struggle to further reduce their OPF, thus hindering further improvements in saturated power. Furthermore, the larger OPF of ridge waveguide and buried heterojunction semiconductor optical amplifiers results in smaller mode field spots, leading to significant input signal power loss during coupling with optical fibers and consequently, higher noise figures. Summary of the Invention

[0006] The purpose of this invention is to provide a strip-channel planar coupled waveguide semiconductor optical amplifier and its fabrication method, which can improve saturation power and reduce noise figure, making the semiconductor optical amplifier suitable for post-amplification of optical power in laser sources or pre-amplification of optical signals in photoelectric conversion units. Therefore, it can find numerous applications in optical communication, optical pumping, optical sensing, and other fields.

[0007] To achieve the above objectives, the present invention provides a strip-channel planar coupled waveguide semiconductor optical amplifier. The semiconductor optical amplifier comprises, from bottom to top, at least an N-type substrate layer, a waveguide layer, and an active region. The waveguide layer includes a strip-channel waveguide region and injection electron confinement regions located on both sides thereof. The strip-channel waveguide region includes a channel waveguide layer and an N-type isolation layer stacked sequentially. The refractive index of the channel waveguide layer is greater than that of the N-type substrate layer, and the refractive index of the N-type isolation layer is lower than that of the active region and the channel waveguide layer located on its upper and lower sides, respectively.

[0008] Preferably, the semiconductor optical amplifier further includes a P-type cladding layer, a P-side ohmic contact layer and a P-side electrode stacked sequentially above the active region, and an N-side electrode located below the N-type substrate layer.

[0009] Preferably, the active region includes N-side confinement layers, multilayer strained quantum well-barrier layers, and P-side confinement layers.

[0010] Preferably, the cross-section of the strip channel waveguide region is rectangular, triangular, or trapezoidal.

[0011] Preferably, the electron-implanted confinement region is a P-type doped epitaxial layer with the same material as the N-type substrate; or the electron-implanted confinement region is a P-type doped layer obtained on the N-type substrate by ion diffusion; or the electron-implanted confinement region is an epitaxial layer with deep-level impurity doping with the same material as the N-type substrate.

[0012] Preferably, adjusting at least one of the following three factors—the thickness of the N-type isolation layer, the material composition of the channel waveguide layer, and the thickness of the channel waveguide layer—can change the optical field confinement factor and the mode field spot size of the semiconductor optical amplifier.

[0013] Preferably, the material of the N-type isolation layer is the same as that of the N-type substrate layer.

[0014] Preferably, the semiconductor optical amplifier uses a P-side surface mount technology.

[0015] This invention also proposes a method for fabricating a strip-channel planar coupled waveguide semiconductor optical amplifier, characterized in that the fabrication method includes:

[0016] S1 provides an N-type substrate layer;

[0017] S2, fabrication of the electron-implanted confinement layer;

[0018] S3, Remove the injected electron confinement layer in the strip channel waveguide region;

[0019] S4, epitaxially growing a channel waveguide layer and an N-type isolation layer in the strip channel waveguide region;

[0020] S5, epitaxial growth of active region, P-cladding and P-side ohmic contact layer;

[0021] S6, Preparation of P-type electrode, thinning of N-type substrate and preparation of N-type electrode.

[0022] Preferably, the optical field confinement factor and mode field spot size of the semiconductor optical amplifier are changed by adjusting at least one of the following: the thickness of the N-type isolation layer, the material composition of the channel waveguide layer, and the thickness of the channel waveguide layer.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The optical field is mainly concentrated in the strip channel waveguide layer and the low-refractive-index isolation layer between it and the active region plate. By changing the thickness of the N-type isolation layer and the material composition or thickness of the channel waveguide layer, the optical field confinement factor and the mode field spot size can be changed in a wide range. By reducing the optical field confinement factor and expanding the mode field spot, the saturation power of the semiconductor optical amplifier can be increased and its noise figure can be reduced, making this type of semiconductor optical amplifier suitable for post-optical power amplification of laser sources or pre-optical signal amplification of photoelectric conversion units.

[0025] (2) Since it is not necessary to prepare ridges on the P side after epitaxial growth of the active region, the series resistance of the optical amplifier can be effectively reduced.

[0026] (3) By combining P-side surface mount technology, thermal resistance can be effectively reduced, thus ensuring that the high-temperature characteristics of the semiconductor optical amplifier do not deteriorate. Its fabrication process is relatively simple and does not require etching of the active region, resulting in a high yield and high reliability of the device products. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the strip channel planar coupled waveguide semiconductor optical amplifier structure proposed in this invention;

[0028] Figure 2 This is a method for fabricating a strip-channel planar coupled waveguide semiconductor optical amplifier;

[0029] Figure 3 This is a schematic diagram of the surface mount installation of a strip channel planar coupled waveguide semiconductor amplifier;

[0030] Figure 4 This is the TE mode light field distribution diagram of Example 1;

[0031] Figure 5 This is the TE mode light field distribution diagram of Example 2;

[0032] Figure 6 This is the TE mode light field distribution diagram of Example 3;

[0033] Figure 7 This is the TE mode light field distribution diagram of Example 4.

[0034] In the figure: 10-Semiconductor optical amplifier; 101-N-type substrate layer; 102-Waveguide layer; 1021-Channel waveguide layer; 1022-N-type isolation layer; 1023-Injected electron confinement region; 103-Active region; 1031-N-side confinement layer; 1032-Multilayer strained quantum well-stacked layer; 1033-P-side confinement layer; 104-P-type cladding; 105-P-side ohmic contact layer; 106-N-side electrode; 107-P-side electrode; 11-Heat sink. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] This invention employs a high-refractive-index strip channel coupled to an active region plate to form a waveguide. This allows the optical field to be more localized within the strip channel, significantly reducing the optical field within the active region plate and effectively lowering the optical field confinement factor. This structure can greatly improve the saturation power of the semiconductor optical amplifier, while the resulting mode field expansion reduces the coupling loss of the input signal, thereby lowering the noise figure.

[0037] like Figure 1 As shown, this invention proposes a strip-channel planar coupled waveguide semiconductor optical amplifier 10, whose structure, from bottom to top, includes an N-side electrode 106, an N-type substrate layer 101, a waveguide layer 102, an active region 103, a P-type cladding layer 104, a P-side ohmic contact layer 105, and a P-side electrode 107. The waveguide layer 102 includes a strip-channel waveguide region and injection electron confinement regions 1023 located on both sides thereof. The strip-channel waveguide region includes a channel waveguide layer 1021 and an N-type isolation layer 1022. The active region 103 may include an N-side confinement layer 1031, a multilayer strained quantum well-barrier layer 1032, and a P-side confinement layer 1033.

[0038] The N-side electrode 106 and P-side electrode 107 are used to connect to an external power supply to provide bias for the optical amplifier. The N-type substrate layer 101 provides support for the optical amplifier. The channel waveguide layer 1021 confines light laterally, allowing the light field to be confined within the active region corresponding to the waveguide, and guides the light longitudinally. The injected electron confinement region 1023 confines the injected electrons in the conduction band laterally, allowing them to pass only through the strip channel waveguide region. The N-type isolation layer 1022 introduces a low-refractive-index isolation layer between the channel waveguide layer 1021 and the active region 103 plate, enabling control of the light field distribution across the cross-section using a planar coupled waveguide (SCW) method. This reduces the overlap between the light field and the active region 103 plate, thereby reducing the light field confinement factor and expanding the mode field spot size; it also ensures that injected electrons in the conduction band passing through this layer can only pass through the strip channel waveguide region, preventing lateral diffusion. The active region 103 provides gain for the optical amplifier. The P-type cladding 104 not only confines the optical field in the vertical direction but also provides valence band hole injection into the active region. The P-side ohmic contact layer 105 is formed to ensure the elimination of the Schottky barrier between the metal and the P-type semiconductor, thus creating an ohmic contact.

[0039] The channel waveguide layer 1021, which provides lateral confinement, is an N-type doped epitaxial layer with a refractive index higher than that of the surrounding N-type substrate layer 101, thus providing lateral confinement for the optical field. The channel waveguide layer 1021 is separated from the active region 103 by a low-refractive-index N-type isolation layer 1022. This lateral optical field confinement is based on a special SCW mechanism rather than the conventional ridge or buried strip waveguide mechanism. The difference lies in that the former achieves optical field confinement through the coupling of two waveguides, while the latter uses only a single waveguide. Vertical confinement of the optical field is provided by the high-refractive-index active region, the strip channel waveguide region, and the low-refractive-index cladding.

[0040] The strip channel waveguide region is a strip channel waveguide, and its cross-sectional shape can be any known shape, such as rectangular, triangular or trapezoidal.

[0041] The N-type isolation layer 1022 has the same width as the strip channel and, optionally, is made of the same material as the N-type substrate layer 101, thus having a low refractive index. Electron injection confinement regions 1023 are located on both sides of the N-type isolation layer 1022, preventing conduction band injected electrons from diffusing laterally to both sides within this layer through the strip channel. The channel waveguide layer 1021 and the active region 103 are separated by the N-type isolation layer 1022, and the distance between them can be adjusted by changing the thickness of the N-type isolation layer 1022.

[0042] Optionally, the electron-implanted confinement region 1023 is a P-type doped epitaxial layer made of the same material as the N-type substrate 101, thus having a low refractive index. Alternatively, the electron-implanted confinement region 1023 is a P-type doped layer obtained on the N-type substrate 101 via ion diffusion. This forms a reverse-biased PN junction, thus preventing conduction band electrons from passing through the P-type layer, thereby restricting electron injection.

[0043] Optionally, the electron-implanted confinement region 1023 is an epitaxial layer with high resistance, such as an epitaxial layer doped with deep-level impurities Fe or Cr. This provides lateral leakage confinement of the conduction band injected electrons while simultaneously confining the lateral optical field using the buried strip channel.

[0044] In some embodiments, the N-type substrate layer 101 further includes a buffer layer.

[0045] This invention also proposes a method for fabricating the above-mentioned strip-channel planar coupled waveguide semiconductor optical amplifier, such as... Figure 2 As shown, the preparation method includes the following steps:

[0046] S1, providing an N-type substrate layer 101. Optionally, the substrate material can be InP or GaAs, etc. When using a GaAs substrate, a low-refractive-index buffer layer needs to be grown on the GaAs substrate to isolate the GaAs with a high refractive index. For ease of description, the following steps use an N-type InP substrate as an example. However, it is understood that those skilled in the art can choose a suitable substrate material according to actual needs.

[0047] S2, Preparation of the implanted electron confinement layer: A P-type InP layer is directly grown on an N-type InP substrate, or a P-type InP layer is obtained on an N-type substrate by Zn diffusion, or an InP layer doped with deep-level impurities such as Fe or Cr is grown by ion implantation or direct epitaxy.

[0048] S3, Forming the Electron Implantation Confinement Region 1023: The electron implantation confinement layer at the strip channel waveguide region is removed using standard photolithography and etching processes. In some embodiments, to precisely control the etching depth of the channel waveguide, an InGaAsP stop etch layer with a thickness of approximately 10 nm and a bandgap of approximately 1050 nm can be grown before the electron implantation confinement layer is grown in the previous step. In this way, when wet etching the channel, the etching depth can be automatically stopped above the pre-fabricated stop etch layer by using an appropriate selective chemical etchant.

[0049] S4, Fabrication of the channel waveguide layer 1021 and the N-type isolation layer 1022: A high-refractive-index material, N-InGaAsP, is epitaxially grown in the previously etched strip-shaped channel waveguide region. Its composition ensures that the bandgap can be freely adjusted under lattice matching with InP, allowing the material's refractive index to be changed according to design requirements. After the high-refractive-index material reaches the required thickness, an N-InP isolation layer continues to grow in the channel, ultimately making the grown N-InP isolation layer flush with the injected electron confinement layer.

[0050] After the above structure is fabricated, only one epitaxial growth step is needed to complete the main process, thus simplifying the fabrication process of the optical amplifier. This structure can serve as a strip channel substrate for semiconductor optical amplifiers. This type of substrate can be used as a standardized prefabricated substrate for semiconductor optical amplifier fabrication. The fabricator only needs to purchase a suitable standard prefabricated substrate with strip channels and directly grow the active region and P-side planar structure on it according to design requirements. There is no need for further oxidation masking and photolithography to fabricate the strips; surface metallization can be performed directly to complete all P-side processes. This fabrication process is more convenient and facilitates process control and yield improvement.

[0051] S5, Epitaxial Growth of Other Layers: Epitaxial growth of active regions, P-InP cladding, and P-side ohmic contact layers, etc. This step can also be combined with the previous step, so that the entire device fabrication process only requires one epitaxial step.

[0052] S6, Electrode fabrication: After the epitaxial growth of each layer of the semiconductor optical amplifier is completed, large-area metallization is performed on the top P side, followed by thinning and metallization of the N-type substrate layer.

[0053] After completing the above steps, conventional processes such as cleaving, coating, preliminary testing, die separation, and surface mount technology (SMT) are also included. Since the P-side is a planar structure and has been extensively metallized, the thickness of the P-InP cladding can be appropriately increased to prevent solder whiskers from climbing up and blocking the light-emitting end face. This allows for the use of... Figure 3 The surface mount technology shown uses a heat sink 11 or a transition heat sink on the P-side to reduce thermal resistance and facilitate heat dissipation.

[0054] The above steps represent a general fabrication process for the semiconductor optical amplifier in this invention. Other methods can also be used in actual fabrication. For example, the cross-sectional shape of the strip channel can also be triangular or trapezoidal. As can be seen from the above steps, the strip channel planar coupled waveguide semiconductor optical amplifier proposed in this invention does not require the fabrication of a ridge waveguide or multiple epitaxy steps. In particular, if the substrate structure with the strip channel can be prefabricated according to certain standard parameters, the fabrication of the optical amplifier becomes simpler and more convenient, and it is also more conducive to process control and yield improvement.

[0055] The TE mode optical field distribution of the semiconductor optical amplifier proposed in this invention can be adjusted by changing the thickness of the N-type isolation layer 1022 and the material composition or thickness of the channel waveguide layer 1021. Here, the TE mode is the fundamental mode of the optical amplifier. When a compressive strain quantum well is used, the TM mode has no gain and therefore does not need to be considered. Therefore, for the TE mode, only the fundamental mode can exist, thus ensuring the spatial single-mode operation of the optical amplifier.

[0056] In Example 1, see Figure 4 The thickness of the N-type isolation layer 1022 is 50 nm, and the thickness of the channel waveguide layer 1021 is 500 nm. The channel waveguide layer 1021 is made of In... 0.90 Ga 0.10 As 0.21 P 0.79 The optical field confinement factor corresponding to the optical amplifier is 1.08%.

[0057] In Example 2, see Figure 5 The thickness of the N-type isolation layer 1022 is 500 nm, the thickness of the channel waveguide layer 1021 is 500 nm, and the channel waveguide layer 1021 is made of In... 0.90 Ga 0.10 As 0.21 P 0.79 The optical field confinement factor corresponding to the optical amplifier is 0.57%.

[0058] In Example 3, see Figure 6 The thickness of the N-type isolation layer 1022 is 500 nm, the thickness of the channel waveguide layer 1021 is 500 nm, and the channel waveguide layer 1021 is made of In... 0.87 Ga 0.13 As 0.30 P 0.70 The optical field confinement factor corresponding to the optical amplifier is 0.22%.

[0059] In Example 4, see Figure 7 The N-type isolation layer 1022 has a thickness of 500 nm, and the channel waveguide layer 1021 has a thickness of 1000 nm. The channel waveguide layer 1021 is made of In... 0.87 Ga 0.13 As 0.30 P 0.70 The optical field confinement factor corresponding to the optical amplifier is 0.02%.

[0060] Comparing Examples 1 and 2, it can be seen that the optical field confinement factor of the structure can be changed by altering the thickness of the N-type isolation layer; the optical field confinement factor decreases as the thickness of the N-type isolation layer increases.

[0061] Comparing Examples 2 and 3, it can be seen that the optical field confinement factor of the structure can be changed by altering the composition of the channel waveguide layer; the optical field confinement factor decreases when the refractive index of the channel waveguide layer increases.

[0062] Comparing Examples 3 and 4, it can be seen that the optical field confinement factor of the structure can be changed by altering the thickness of the channel waveguide layer; the optical field confinement factor decreases as the thickness of the channel waveguide layer increases.

[0063] Comparing Examples 1 and 4, it can be seen that by changing the design of the strip channel waveguide region and the thickness of the low-refractive-index N-type isolation layer, the optical field confinement factor of this structure can decrease by 50 times (0.02%) from an order of magnitude (~1%) comparable to that of a conventional ridge or buried strip waveguide. Furthermore, the light spot in Example 4 is closer to a circle than in Example 1, thus being more conducive to coupling with optical fibers.

[0064] Compared to traditional ridge waveguide semiconductor optical amplifiers, the advantages of this invention are as follows: the P-side of the strip-channel planar coupled waveguide semiconductor optical amplifier above the active region is entirely composed of a uniform planar layer, eliminating the need for any lateral confinement structures and allowing the fabrication of the entire device's planar electrodes without the need for strip electrodes. Since the series resistance of the semiconductor optical amplifier mainly originates from the semiconductor-metal ohmic contact resistance on the P-side surface and the bulk resistance of the P-type material with a low doping concentration, removing the lateral strip confinement on the P-side significantly increases its equivalent cross-sectional area. This simultaneously reduces both surface contact resistance and bulk resistance, resulting in a decrease in the overall series resistance of the device.

[0065] Since the thickness of the P-side cladding no longer restricts carriers and the optical field, its thickness can be arbitrarily adjusted according to the requirements of the P-side mounting. For example, it can be thickened according to reliability requirements or different mounting methods such as eutectic bonding or brazing. This method of mounting with a close-fitting heat sink (or transition heat sink) on the P-side significantly reduces the thermal resistance of the device, which is beneficial for the semiconductor optical amplifier to operate at high power output and high temperature environments. The strip channel and the active region are separated by an N-type isolation layer made of low-refractive-index material. By adjusting the thickness of this layer, based on the principle of planar coupled waveguides, the optical field confinement factor of the active region can be greatly reduced, thereby significantly improving the saturation power of the semiconductor optical amplifier. Simultaneously, the significant expansion of the guided light spot under the SCW mechanism makes coupling between the semiconductor optical amplifier and the optical fiber easier and significantly improves its coupling efficiency. This effectively reduces the noise figure of the semiconductor optical amplifier; otherwise, input coupling loss would directly lead to the loss of input signal power without affecting noise, resulting in a direct decrease in the output signal-to-noise ratio.

[0066] Furthermore, since the fabrication and burial of the strip channels can be prefabricated on the substrate side, the semiconductor optical amplifier process after epitaxial growth of the active region does not require any strip fabrication. This fabrication process is more convenient and more conducive to process control and yield improvement.

[0067] The present invention has been described above with reference to specific embodiments. These descriptions are merely illustrative and should not be construed as limiting the scope of protection of the present invention in any way. Based on the explanation herein, those skilled in the art can readily conceive of other specific embodiments of the present invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A slab-coupled waveguide semiconductor optical amplifier having a bar channel, characterized in that, The semiconductor optical amplifier comprises, from bottom to top, an N-side electrode, an N-type substrate layer, a waveguide layer, an active region, a P-type cladding layer, a P-side ohmic contact layer and a P-side electrode, wherein the P-type cladding layer, the P-side ohmic contact layer and the P-side electrode are all planar structures; the waveguide layer comprises a strip-shaped channel waveguide region and electron-injection confinement regions located on both sides of the strip-shaped channel waveguide region, the strip-shaped channel waveguide region comprises a channel waveguide layer and an N-type isolation layer which are stacked in sequence, and the N-type isolation layer has the same width as the strip-shaped channel; the refractive index of the channel waveguide layer is greater than the refractive index of the N-type substrate layer, and the refractive index of the N-type isolation layer is lower than the refractive indexes of the active region and the channel waveguide layer located on the upper and lower sides of the N-type isolation layer respectively.

2. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, The active region comprises N-side separate confinement layers, a multilayer strain quantum well-bar stack and P-side separate confinement layers.

3. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, The cross section of the strip-shaped channel waveguide region is rectangular, triangular or trapezoidal.

4. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, The electron-injection confinement regions are P-type doped epitaxial layers with the same material as the N-type substrate layer; or the electron-injection confinement regions are P-type doped layers obtained on the N-type substrate layer by ion diffusion; or the electron-injection confinement regions are epitaxial layers doped with deep-level impurities and have the same material as the N-type substrate layer.

5. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, Adjusting at least one of the thickness of the N-type isolation layer, the material composition of the channel waveguide layer and the thickness of the channel waveguide layer can change the optical field confinement factor and the mode field spot size of the semiconductor optical amplifier.

6. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, The material of the N-type isolation layer is the same as that of the N-type substrate layer.

7. The bar-channel slab-coupled waveguide semiconductor optical amplifier of claim 1, wherein, The semiconductor optical amplifier adopts a P-side patch process.

8. A method of fabricating a bar-channel slab-coupled waveguide semiconductor optical amplifier as claimed in any one of claims 1 to 7, characterised by, The preparation method comprises: S1, providing an N-type substrate layer; S2, preparing an electron-injection confinement layer; S3, removing the electron-injection confinement layer at the strip-shaped channel waveguide region; S4, epitaxially growing a channel waveguide layer and an N-type isolation layer at the strip-shaped channel waveguide region; S5, epitaxially growing an active region, a P-type cladding layer and a P-side ohmic contact layer; S6, preparing a P-type electrode, thinning the N-type substrate layer and preparing an N-type electrode.

9. The production method according to claim 8, characterized by, Adjusting at least one of the thickness of the N-type isolation layer, the material composition of the channel waveguide layer and the thickness of the channel waveguide layer can change the optical field confinement factor and the mode field spot size of the semiconductor optical amplifier.

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