A method for manufacturing a semiconductor optical amplifier and a structure thereof

Abstract

The application discloses a manufacturing method and structure of a semiconductor optical amplifier, and the method comprises the following steps: arranging a substrate surface, and sequentially dividing the substrate surface into a first mode spot converter area, a first amplification area, a second amplification area and a second mode spot converter area along a length direction; growing a buffer layer material on the substrate; manufacturing a preset mask pair pattern on the buffer layer material; growing a waveguide material on the buffer layer material which is not covered by the mask pair pattern; removing the mask pair pattern, and growing an active material on the buffer layer material which is originally covered by the mask pair pattern; removing the active material in the first mode spot converter area and the second mode spot converter area; sequentially growing a cladding layer material and a contact layer material on the remaining active material, and completing the manufacturing of the semiconductor optical amplifier. The manufacturing method provided by the application can make the manufactured device have high gain and high saturated output characteristics, and has the advantages of small far-field divergence angle and high optical fiber coupling efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optical integrated device technology, and in particular to a method and structure for fabricating a semiconductor optical amplifier. Background Technology

[0002] With the rapid development of information technology, optical communication, photonics, and optical sensing are quickly becoming important components of modern technology and communication systems. Semiconductor optical amplifiers (SOAs) have broad application prospects in optical communication, Si-based photonics, and optical sensing. Improving the gain and saturation output power of SOAs is crucial for enhancing the quality of optical signal transmission, increasing the transmission distance of optical communication systems, and improving system stability. Therefore, in-depth research on how to balance gain and output power in the same device to meet the needs of different fields has become an important direction in current optoelectronics research.

[0003] Currently, there are certain technical bottlenecks in improving the gain and saturated output power of SOA. Increasing gain typically requires a large optical confinement factor in the active material, thereby increasing the interaction between light and the material. However, this process easily leads to nonlinear effects and self-excitation problems in the material, limiting further gains. Increasing saturated output power, on the other hand, requires reducing the optical confinement factor in the active material to achieve higher optical power output, which contradicts the need for gain improvement. Furthermore, the longitudinal far field of SOA output light is larger than its lateral far field, resulting in lower coupling efficiency with optical fibers or other types of waveguides, thus affecting the effectiveness of its optical amplification.

[0004] Therefore, this invention proposes a method and structure for fabricating a semiconductor optical amplifier that can simultaneously possess high gain and high saturation output characteristics, as well as a small far-field divergence angle and high coupling efficiency with optical fibers. Summary of the Invention

[0005] In view of this, the present invention provides a method and structure for manufacturing a semiconductor optical amplifier, which solves the technical problems in the prior art where it is impossible to increase saturated output power while increasing gain, and where the longitudinal far field of the output light of the semiconductor optical amplifier is significantly larger than the transverse far field, resulting in low coupling efficiency with optical fiber or other types of waveguides, which is not conducive to the optical amplification function of the semiconductor optical amplifier.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for manufacturing a semiconductor optical amplifier, comprising: The substrate surface is laid out by dividing it into a first mode converter region, a first amplification region, a second amplification region, and a second mode converter region along its length; a buffer layer material is grown on the substrate. A mask pair pattern is fabricated on a buffer layer material; wherein the mask pair pattern includes identical patterns arranged symmetrically, each pattern including a first right-angled triangle, a first rectangle, a transition trapezoid, a second rectangle, and a second right-angled triangle connected in sequence; the first right-angled triangle is located within a first speckle converter area, with one right-angled side having a length of a first width value and the other right-angled side having a length equal to the length of the first speckle converter area; the first rectangle is located within a first magnification area, with a width equal to the first width value; the second rectangle is located within a second magnification area, with a width equal to the second width value, and the first width value being less than the second width value; the transition trapezoid is a trapezoid at the intersection of the first and second rectangles, with the upper base being the first width value and the lower base being the second width value; the second right-angled triangle is located within a second speckle converter area, with one right-angled side having a length of the second width value and the other right-angled side having a length equal to the length of the second speckle converter area; Waveguide material is grown on a buffer layer material that is not covered by a mask pattern; Remove the mask pair pattern and grow active material on the buffer layer material originally covered by the mask pair pattern; Remove the active material from the first and second mode-spot converter regions; The cladding material and contact layer material are grown sequentially on the remaining active material to complete the fabrication of the semiconductor optical amplifier.

[0007] Furthermore, the substrate material is one of InP, GaAs, or GaN.

[0008] Furthermore, the waveguide material is InGaAsP.

[0009] Furthermore, the bandgap wavelength of the waveguide material is smaller than the operating wavelength of the first amplification region and the second amplification region.

[0010] Furthermore, the waveguide material is grown using MOCVD technology.

[0011] Furthermore, the active material is either a quantum well material or a bulk material.

[0012] Furthermore, the method for removing the active material from the first and second speckle converter regions is wet etching.

[0013] Furthermore, the cladding material is either InP or AlGaAs.

[0014] Furthermore, the contact layer material is doped InGaAs or GaAs.

[0015] On the other hand, the present invention also provides a semiconductor optical amplifier structure, wherein the semiconductor optical amplifier is fabricated using the manufacturing method described in the above technical solution, and the semiconductor optical amplifier comprises, from bottom to top, a substrate, a buffer layer, a waveguide layer, an active layer and a contact layer; the surface of the substrate is divided along the length direction into a first mode converter region, a first amplification region, a second amplification region and a second mode converter region. The active layer thickness of the first amplification region is smaller than that of the second amplification region. The waveguide material thickness of the first mode converter region gradually decreases from the side closer to the first amplification region to the side farther away from the first amplification region. The waveguide material thickness of the second mode converter region gradually decreases from the side closer to the second amplification region to the side farther away from the second amplification region.

[0016] Compared with existing technologies, the present invention offers the following advantages: (1) By using a special mask to precisely control the thickness of the waveguide material in the pattern, the waveguide material located below the active material in the amplification area has different optical confinement factors. This design enables the device to have both high gain and high saturation output power, effectively solving the contradiction between increasing gain and saturation output power in the prior art, thereby improving the optical amplification efficiency of semiconductor optical amplification devices.

[0017] (2) By controlling the thickness of the waveguide material, this method integrates a first mode-spot converter and a second mode-spot converter in a semiconductor optical amplifier device. These mode-spot converters effectively reduce the far-field divergence angle of the device, thereby reducing the coupling loss between the device and the single-mode fiber, making the coupling between the semiconductor optical amplifier device and the fiber more efficient, and thus improving the transmission quality of the optical signal.

[0018] (3) By integrating the mode converter, the far-field divergence angle of the device is effectively controlled, which means that the degree of beam diffusion at the output is greatly reduced, and the energy loss is also reduced, thereby reducing the direct improvement of the transmission efficiency and stability of the system.

[0019] This invention resolves the contradiction between gain and saturated output power in SOA technology through precise material and structural control, while significantly improving the coupling efficiency between the device and the optical fiber, thereby enhancing the overall performance, transmission quality, and system stability of the optical amplifier. By optimizing the optical field distribution, the optical amplifier can transmit optical energy more efficiently, demonstrating significant advantages, especially in high-power, high-efficiency optical amplification applications. It not only improves the transmission quality of optical communication systems but also increases the transmission distance of optical signals and reduces signal attenuation during transmission, making it highly practical. Attached Figure Description

[0020] Figure 1A schematic flowchart illustrating the fabrication method of the semiconductor optical amplifier provided by the present invention; Figure 2 A schematic diagram of the substrate region division and mask pair pattern provided by the present invention; Figure 3 This is a schematic diagram of the structure after the active material is grown according to the present invention. Figure 4 This is a schematic diagram of the structure provided by the present invention after removing the active material in the speckle converter region; Figure 5 A schematic diagram of the structure of the completed semiconductor optical amplifier provided by the present invention; In the figure, 10 is the substrate, 20 is the buffer layer material, 30 is the waveguide material, 40 is the active material, 50 is the cladding material, 60 is the contact layer material, and 21 is the mask pair pattern. Detailed Implementation

[0021] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0022] Example 1

[0023] Please see Figure 1 , Figure 1 This embodiment illustrates a flowchart of a method for fabricating a semiconductor optical amplifier, which includes: Step S101: The substrate surface is laid out by dividing the substrate surface along the length direction into a first mode converter region, a first amplification region, a second amplification region, and a second mode converter region. Step S102: Grow a buffer layer material on the substrate; Step S103: Fabricate a mask pair pattern on the buffer layer material; wherein, the mask pair pattern includes two identical patterns arranged symmetrically, each pattern including a first right-angled triangle, a first rectangle, a transition trapezoid, a second rectangle, and a second right-angled triangle connected in sequence; the first right-angled triangle is located within the first mode converter area, and one right-angled side has a length of a first width value, and the other right-angled side has a length of the first mode converter area; the first rectangle is located within the first magnification area, with its outer side flush with the edge of the substrate and its width being the first width value; the second rectangle is located within the second magnification area, with its outer side flush with the edge of the substrate and its width being the second width value, and the first width value is less than the second width value; the transition trapezoid is a trapezoid at the intersection of the first rectangle and the second rectangle with its upper base being the first width value and its lower base being the second width value; the second right-angled triangle is located within the second mode converter area, and one right-angled side has a length of the second width value, and the other right-angled side has a length of the second mode converter area; Step S104: Grow waveguide material on the buffer layer material that is not covered by the mask pattern; Step S105: Remove the mask pair pattern and grow active material on the buffer layer material originally covered by the mask pair pattern and the grown waveguide material; Step S106: Remove the active material from the first and second modulus converter regions; Step S107: Grow cladding material and contact layer material on the remaining active material to complete the fabrication of the semiconductor optical amplifier.

[0024] The semiconductor amplifier fabrication method provided in this embodiment uses a dielectric mask to pattern the waveguide material beneath the active material, thereby controlling the growth thickness and enabling the active materials of the two tandemly connected amplification regions to have different optical confinement factors. This allows the entire semiconductor optical amplifier device to simultaneously possess high gain and high saturation output characteristics. Furthermore, by utilizing the mask pattern to control the waveguide material thickness, a first mode converter and a second mode converter are integrated into the semiconductor optical amplifier device, effectively reducing the far-field divergence angle and resulting in very low coupling loss between the device and the single-mode fiber. Therefore, the optical amplifier device fabricated using this method has significant advantages in high-performance optical amplification applications.

[0025] In a preferred embodiment, the substrate material is one of InP, GaAs, or GaN.

[0026] In a preferred embodiment, the waveguide material is InGaAsP.

[0027] In a preferred embodiment, the bandgap wavelength of the waveguide material is smaller than the operating wavelength of the first amplification region and the second amplification region.

[0028] In a preferred embodiment, the waveguide material is grown using MOCVD technology.

[0029] In a preferred embodiment, the active material is either a quantum well material or a bulk material.

[0030] In a preferred embodiment, the method for removing the active material from the first and second speckle converter regions is wet etching.

[0031] In a preferred embodiment, the cladding material is either InP or AlGaAs.

[0032] In a preferred embodiment, the contact layer material is doped InGaAs or GaAs.

[0033] The following is combined with Figures 2-5 The above steps will be demonstrated and explained in detail.

[0034] As a specific embodiment, the steps of the manufacturing method include: (1) As shown in Figure 2 , a substrate 10 is sequentially divided along the length direction into a first spot converter region (SSC1 region), a first amplification region (SOA1 region), a second amplification region (SOA2 region) and a second spot converter region (SSC2 region); a buffer layer material 20 is grown on the substrate 10; the substrate is one of InP, GaAs, GaN or other semiconductor materials. In this embodiment, the substrate 10 is an N-type InP substrate, and the buffer layer material 20 is an N-type InP buffer material.

[0035] (2) Fabricating a silicon oxide or silicon nitride dielectric mask pair pattern 21 on the buffer layer material 20; wherein the mask pair pattern 21 comprises two identical symmetrical patterns, as shown in Figure 2 , the spacing between the two patterns is o, the pattern is provided with a first rectangle in the SOA1 region, the outer side of which is flush with the edge of the substrate 10 and has a width of w1, and a second rectangle in the SOA2 region, the outer side of which is flush with the edge of the substrate 10 and has a width of w2, and w1<w2; during the gradual change of the mask width in the region between the SOA1 region and the SOA2 region, a transition trapezoid with an upper base of w1 and a lower base of w2 is formed; in the SSC1 region, the width of the first rectangle is reduced from w1 to 0 to form a first right triangle, and in the SSC2 region, the width of the second rectangle is reduced from w2 to 0 to form a second right triangle.

[0036] (3) Growing a waveguide material 30 on the buffer layer material 20 on which the mask pair pattern 21 has been fabricated, the waveguide material 30 being an InGaAsP material whose bandgap wavelength is smaller than the operating wavelengths of the SOA1 region and the SOA2 region.

[0037] It should be noted that, when the waveguide material 30 is grown by using technologies such as MOCVD, the material cannot grow on the surface of the mask pair pattern 21, so the reactants on the mask surface diffuse to the middle region of the thin film, which increases the growth rate of the material in the middle region of the thin film.

[0038] Therefore, under the condition that the mask spacing is equal, the larger the mask width is, the higher the growth rate of the material in the region between the masks is. Therefore, since w1<w2, the thickness t1 of the waveguide material 30 in the SOA1 region is smaller than the thickness t2 of the waveguide material 30 in the SOA2 region. In addition, the formation of the transition trapezoid through the linear change from w1 to w2 is beneficial to reducing the influence of thickness mutation between the two regions. In the SSC1 region and the SSC2 region, since the mask width gradually decreases, the thickness of the waveguide material in the SSC1 region decreases from t1 to t0, and the thickness of the waveguide material in the SSC2 region decreases from t2 to t0.

[0039] (4) As shown in Figure 3As shown, after removing the mask from pattern 21, an active material 40 is grown. The active material 40 can be a quantum well material or a bulk material.

[0040] (5) Remove the active material 40 from the pattern converter area, i.e., the SSC1 and SSC2 areas, and retain the active material 40 in other areas, such as Figure 4 As shown.

[0041] (6) Cladding material 50 and contact layer material 60 are sequentially grown on the remaining active material 40 to complete the fabrication of the semiconductor optical amplifier, such as... Figure 5 As shown.

[0042] By manipulating the growth thickness of the waveguide material beneath the active material using a dielectric mask, the active materials of the two tandem amplification regions, SOA1 and SOA2, possess different optical confinement factors. This results in the entire semiconductor optical amplifier device exhibiting both high gain and high saturation output characteristics. Furthermore, by utilizing the mask's pattern to control the waveguide material thickness, a mode converter is integrated into the semiconductor optical amplifier device, effectively reducing the far-field divergence angle. This leads to very low coupling loss between the device and the single-mode fiber, thereby improving the overall performance and stability of the device. By optimizing the optical field distribution and reducing the far-field divergence angle, SOA can transmit optical energy into the fiber more efficiently, reducing energy loss and thus improving the transmission quality and distance of the optical communication system.

[0043] The method of this invention has important practical application value in the fields of optical communication and photonics, especially in the need for high-efficiency and high-power optical amplification.

[0044] Example 2

[0045] This invention provides a semiconductor optical amplifier structure, such as... Figure 5 As shown, the semiconductor optical amplifier is fabricated using the method described in Example 1. The semiconductor optical amplifier comprises, from bottom to top, a substrate 10, a buffer layer material 20, a waveguide material 30, an active material 40, a cladding material 50, and a contact layer material 60. The surface of the substrate 10 is divided along its length into a first mode converter region (SSC1 region), a first amplification region (SOA1 region), a second amplification region (SOA2 region), and a second mode converter region (SSC2 region). The active layer thickness of the first amplification region is smaller than that of the second amplification region. The waveguide material thickness of the first mode converter region gradually decreases from the side closer to the first amplification region SOA1 to the side farther away from the first amplification region SOA1. The waveguide material thickness of the second mode converter region gradually decreases from the side closer to the second amplification region SOA2 to the side farther away from the second amplification region SOA2.

[0046] In the semiconductor optical amplifier provided in this embodiment, the waveguide material thickness t1 beneath the active material (quantum well material) in the SOA1 region is relatively small, resulting in a high confinement factor for light within the quantum well material, which is beneficial for obtaining high optical gain. In contrast, the waveguide material layer thickness t2 beneath the quantum well material in the SOA2 region is relatively large, resulting in a low confinement factor for light within the quantum well material, which is beneficial for obtaining high saturated output optical power. By connecting SOA1 and SOA2 in series, the entire device can simultaneously possess high gain and high saturated output characteristics. In the SSC1 and SSC2 regions, light is confined only within the waveguide material. As the waveguide material thickness gradually decreases, the light confinement gradually weakens, the spatial distribution range of the optical field increases, thereby reducing the far-field divergence angle and improving the coupling efficiency between the chip and the optical fiber.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a semiconductor optical amplifier, characterized in that, include: The substrate surface is laid out by dividing it into a first mode converter region, a first amplification region, a second amplification region, and a second mode converter region along its length; a buffer layer material is grown on the substrate. A mask pair pattern is fabricated on a buffer layer material; wherein the mask pair pattern comprises two identical patterns arranged symmetrically, with a gap between the two identical patterns; each pattern comprises a first right-angled triangle, a first rectangle, a transition trapezoid, a second rectangle, and a second right-angled triangle connected in sequence; the first right-angled triangle is located within a first pattern converter area, with one right-angled side having a length of a first width value and the other right-angled side having a length equal to the length of the first pattern converter area; the first rectangle is located within a first magnification area, with a width equal to the first width value; the second rectangle is located within a second magnification area, with a width equal to the second width value, and the first width value being less than the second width value; the transition trapezoid is a trapezoid at the intersection of the first and second rectangles, with the upper base being the first width value and the lower base being the second width value; the second right-angled triangle is located within a second pattern converter area, with one right-angled side having a length of the second width value and the other right-angled side having a length equal to the length of the second pattern converter area; A waveguide material is grown on a buffer layer material that is not covered by a mask pattern; the waveguide material is InGaAsP; the bandgap wavelength of the waveguide material is smaller than the operating wavelength of the first amplification region and the second amplification region; the difference in growth rate is used to make the thickness of the first amplification region smaller than the thickness of the second amplification region. Remove the mask pair pattern and grow active material on the buffer layer material and the waveguide material originally covered by the mask pair pattern; The active material in the first and second speckle converter regions is removed; the method for removing the active material in the first and second speckle converter regions is wet etching. The cladding material and contact layer material are grown sequentially on the remaining active material to complete the fabrication of the semiconductor optical amplifier.

2. The method for fabricating a semiconductor optical amplifier according to claim 1, characterized in that, The substrate material is one of InP, GaAs, or GaN.

3. The method for fabricating a semiconductor optical amplifier according to claim 1, characterized in that, The waveguide material is grown using MOCVD technology.

4. The method for fabricating a semiconductor optical amplifier according to claim 1, characterized in that, The active material is either a quantum well material or a bulk material.

5. The method for fabricating a semiconductor optical amplifier according to claim 1, characterized in that, The cladding material is either InP or AlGaAs.

6. The method for fabricating a semiconductor optical amplifier according to claim 1, characterized in that, The contact layer material is doped InGaAs or GaAs.

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