A semiconductor multi-wavelength laser device and its fabrication method

Abstract

This invention provides a semiconductor multi-wavelength laser device. The laser grating structure employs a linearly graded grating structure to increase the laser's bandgap. The overall laser grating structure is divided into multiple segments, and the designed overall grating exhibits a gradual, periodic change within the laser cavity. Multi-wavelength lasing wavelengths and wavelength intervals are achieved by controlling the periodic change of the overall grating. Phase shifts are introduced between each grating segment to achieve phase matching, and the laser possesses a multi-phase-shift structure, thereby realizing multi-wavelength lasing output. The semiconductor multi-wavelength laser device of this invention is constructed from bottom to top as follows: a substrate, a buffer layer, a lower confinement layer, a multiple quantum well layer, an upper confinement layer, a grating layer, an etch-blocking layer, a waveguide layer, and a contact layer, all stacked together. The grating layer is composed of laser gratings. This invention offers advantages such as single-laser multi-wavelength output, simple structure, low power consumption, and high integration.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a semiconductor multi-wavelength laser device and its fabrication method. Background Technology

[0002] In recent years, many emerging fields, especially artificial intelligence, have pursued powerful computing power. However, a simple neural network may contain hundreds of millions of parameters. To achieve good results, a network often needs to be continuously trained, which means massive computations. Limited by technological and physical constraints, Moore's Law is approaching its physical limits, making traditional electronic hardware unable to handle such massive data streams. Light waves can be multiplexed by time, space, wavelength, polarization, and mode, providing natural parallel computing capabilities. Convolutional neural networks can be implemented on light. Photonic Convolutional Neural Networks (PCNNs) mainly consist of photonic convolutional layers and electronically fully connected layers, with the photonic convolutional layers performing feature extraction. Multi-wavelength sources can be used as light sources. The optical power of each wavelength in the multi-wavelength source is adjusted to apply different weights, carrying signals through different wavelengths. These signals are used as flattened convolution kernels, which, along with the electrical signals generated by the signal generator, are fed into the modulator to perform matrix convolution with the original image matrix. The demand for multi-wavelength sources is increasing dramatically. Furthermore, to facilitate integration with subsequent structures, multi-wavelength output from a single laser is required.

[0003] Simultaneously, with the shift towards coherent communication, more scenarios are beginning to adopt coherent communication. The photoelectric conversion process requires light source output and coherent multi-wavelength output. Considering compatibility with existing systems, high integration of multi-wavelength sources is required.

[0004] Currently, there is a lack of a multi-wavelength source with high integration, simple structure, and low power consumption. In view of the current situation, this invention proposes a semiconductor multi-wavelength laser device and its fabrication method. Summary of the Invention

[0005] In response to the problems raised in the background art, this invention provides a semiconductor multi-wavelength laser device and its fabrication method that can achieve multi-wavelength output from a single laser, has a simple structure, low power consumption, and high integration.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A semiconductor multi-wavelength laser device includes a laser grating, wherein the laser grating is divided into multiple grating units, and the grating period of the grating units between the segments gradually changes.

[0007] To optimize the above technical solution, the specific measures also include: The grating period of the above-mentioned grating unit changes gradually within its segment, and the overall grating period of the laser grating changes linearly.

[0008] A phase-shifting structure is set between each grating unit segment. The phase-shifting structure enables adjacent grating units to achieve phase matching. The semiconductor multi-wavelength laser device has multiple phase-shifting structures to achieve multi-wavelength lasing output.

[0009] The aforementioned semiconductor multi-wavelength laser device is composed of a substrate, a buffer layer, a lower confinement layer, a multiple quantum well layer, an upper confinement layer, a grating layer, an etching barrier layer, a waveguide layer, and a contact layer stacked from bottom to top. The grating layer is composed of a laser grating.

[0010] The aforementioned multi-quantum-well layer serves as a gain medium covering the wavelength output range of the semiconductor multi-wavelength laser device.

[0011] The substrate described above is an n-type doped substrate, and the lower confinement layer is an n-type doped and undoped confinement layer.

[0012] The aforementioned multi-quantum-well layer is an InGaAlAs multi-quantum-well.

[0013] A method for fabricating a semiconductor multi-wavelength laser device, using the aforementioned semiconductor multi-wavelength laser device, specifically includes the following steps: Step 1: A buffer layer and a lower confinement layer are sequentially grown on the substrate using metal-organic chemical vapor deposition. Then, a multi-quantum-well layer is grown on the lower confinement layer, followed by an upper confinement layer. Finally, a grating layer is grown above the upper confinement layer. Step 2: The grating layer is a laser grating, designed using reconstructed equivalent chirp technology to make the grating period of the laser grating linearly and gradually change. Step 3: Grow InP above the grating layer to bury the grating layer, and then grow an etch barrier layer, a waveguide layer and a contact layer sequentially on the upper buffer layer.

[0014] The present invention has the following advantages: The laser of this invention employs a linearly graded grating structure. The grating period of the linearly graded grating structure gradually increases or decreases, thereby enhancing grating feedback, increasing the bandgap of the laser, and covering the lasing wavelength range. The entire grating structure is divided into multiple segments, with a phase shift introduced between each segment. The linearly graded grating structure is maintained between segments, and the laser resonator at the phase shift point achieves phase matching, realizing single-mode output. Each laser uses a single electrode for power application, and all phase shifts share a single laser resonator, achieving flattened output across all wavelengths.

[0015] The number of output wavelengths in this invention can be increased by increasing the number of phase shifts, and the wavelength interval can be achieved by varying the overall period of a linear gradient grating. This invention enables multi-wavelength coherent planarization output from a single laser, providing a simple, low-power, and highly integrated multi-wavelength source design for optical computing and coherent communication. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the multi-wavelength laser of the present invention, wherein 101 is the first phase shift, that is, the phase shift structure between the first grating and the second grating, 102 is the second phase shift, 103 is the third phase shift, 104 is the fourth phase shift, and 105 is the fifth phase shift; Figure 2 This is a design diagram of the gradient grating for the multi-wavelength laser of the present invention; Figure 3 The image shows a simulation of the transmission spectrum of a 5-channel laser. In the image, 301 is the first transmission peak introduced by the first phase shift 101 of the designed multi-wavelength structure, 302 is the second transmission peak introduced by the second phase shift 102, 303 is the third transmission peak introduced by the third phase shift 103, 304 is the fourth transmission peak introduced by the fourth phase shift 104, and 305 is the fifth transmission peak introduced by the fifth phase shift 105.

[0017] Figure 4 The image shows the actual spectrum of the 5-channel laser in the embodiment. 401 represents the first wavelength lasing peak, 402 represents the second wavelength lasing peak, 403 represents the third wavelength lasing peak, 404 represents the fourth wavelength lasing peak, and 405 represents the fifth wavelength lasing peak. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0019] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0020] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0021] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or units (elements) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or apparatus. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms “multiple” / “several” used in this application refer to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can indicate: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0022] A semiconductor multi-wavelength laser device is disclosed. The laser grating structure employs a linearly graded grating structure to increase the bandgap of the laser. The overall laser grating structure is divided into multiple segments, and the designed overall grating exhibits a gradual change within the laser cavity, changing periodically. By controlling the periodic change of the overall grating, the multi-wavelength lasing wavelength and wavelength spacing are achieved.

[0023] The laser introduces phase shifts between the grating segments to achieve phase matching. The laser has a multi-phase shift structure, thereby realizing multi-wavelength lasing output.

[0024] The semiconductor multi-wavelength laser device of the present invention is composed of a substrate, a buffer layer, a lower confinement layer, a multiple quantum well layer, an upper confinement layer, a grating layer, an etching barrier layer, a waveguide layer and a contact layer stacked from bottom to top, wherein the grating layer is composed of a laser grating.

[0025] The laser of this invention adopts a multi-quantum-well structure, with the quantum wells serving as the gain medium to provide the required gain, and the gain spectrum design covers the wavelength output range.

[0026] The linear gradient grating structure and the phase shift structure between each grating segment can be realized using the reconstructed equivalent chirp technique proposed by Chen Xiangfei et al., which utilizes the equivalent grating structure to achieve the equivalent linear gradient.

[0027] The laser of the present invention uses the same laser resonator cavity for all wavelengths, which can realize flattened output of each wavelength of the laser and can use a single electrode structure to inject equal density carrier concentration.

[0028] The technical solution of the present invention will be explained below using Example 1: Embodiment 1 of the present invention provides a multi-wavelength source design for a single laser, such as... Figure 1 As shown, the laser of the present invention includes a linear gradient grating, and a phase shift structure exists at six equal divisions of the overall grating.

[0029] Example Simulation Analysis: The multi-wavelength source of the present invention enhances the continuity within the bandgap through a linear gradient grating structure, providing feedback for multiple wavelengths.

[0030] Optionally, the multi-wavelength source can use an n-type doped substrate. An n-type doped InP buffer layer, an n-type doped confinement layer, and an undoped confinement layer are sequentially grown on the substrate via metal-organic compound vapor deposition. The confinement layers are used to confine the optical field and restrict charge carriers. An InGaAlAs multi-quantum-well structure is then grown.

[0031] A confinement layer is designed above the quantum well, and an InGaAsP grating layer is grown above the confinement layer. Its structure is the linearly graded grating period involved. The equivalent linearly graded grating can be designed using the reconstructed equivalent chirp technique, and its equivalent grating period is linearly graded.

[0032] p-type InP is grown above the grating layer for burial, and a waveguide-related corrosion barrier layer is grown above the contact layer, followed by waveguide layer growth.

[0033] In Example 1, multiple phase shifts with equal spacing are introduced into the period of a linearly graded grating. The wavelength variation of the Bragg grating of the entire laser is set to 4.8 nm. Simulation of the linearly graded grating shows an increased bandgap, ensuring that all wavelengths can resonate within the same bandgap.

[0034] The linearly graded grating's Bragg wavelength varies from 1550 nm to 1554.8 nm, with five phase shifts introduced in between. The spacing between each phase shift is 0.8 nm. Thus, the first and second grating segments share a single phase shift, similar to the single-phase-shift structure described above. This allows two grating segments to share a single phase shift.

[0035] The transmission spectrum indicates that the five wavelengths of the lasing correspond to the Bragg wavelengths of the phase shifts at various points, namely 1550.8 nm, 1551.6 nm, 1552.4 nm, 1553.2 nm, and 1554.0 nm. The five peaks correspond to five lasing wavelengths, and simultaneously... Figure 2 As shown, the five channels can maintain a near-low threshold gain and a very high threshold gain difference, thereby reducing the threshold current at each wavelength and exhibiting excellent single-mode characteristics. Consequently, upon subsequent power-up, the overall threshold current at all four wavelengths decreases, improving the photoelectric conversion efficiency.

[0036] The test results related to the above design embodiments are as follows: Figure 3 As shown, the spectral test results indicate that the laser can emit five wavelengths in actual use, with uniform channel spacing, relatively flat output power, and high side-mode suppression. Therefore, it can be concluded that the designed 5-channel multi-wavelength laser can be applied to the aforementioned related application fields.

[0037] In summary, this invention provides a multi-wavelength source design scheme that employs a linearly graded grating structure to increase the bandgap and provide feedback for multiple wavelengths. Phase shifts are introduced at the equal divisions of the overall grating to achieve lasing of multiple Bragg wavelengths at the phase shift locations. Each wavelength has a low threshold gain, reducing the overall laser threshold current and increasing photoelectric conversion efficiency. Furthermore, because they share the same resonant cavity, they can output flattened coherent wavelengths.

[0038] This invention ultimately achieves multi-wavelength output from a single laser, with a simple structure, low power consumption, and high integration.

[0039] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0040] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A semiconductor multiwavelength laser device comprising a laser grating, characterized by: The laser grating is divided into multiple grating units, with the grating period of the grating units between the segments gradually changing; the grating period of the grating unit within the segment gradually changing, and the overall grating period of the laser grating gradually changing linearly. The semiconductor multi-wavelength laser device is composed of a substrate, a buffer layer, a lower confinement layer, a multiple quantum well layer, an upper confinement layer, a grating layer, an etching barrier layer, a waveguide layer, and a contact layer stacked from bottom to top, wherein the grating layer is composed of a laser grating; The substrate is an n-type doped substrate, and the lower confinement layer is an n-type doped and undoped confinement layer; The aforementioned multi-quantum well layer is an InGaAlAs multi-quantum well.

2. The semiconductor multi-wavelength laser device according to claim 1, characterized in that: A phase-shifting structure is set between each grating unit segment. The phase-shifting structure enables adjacent grating units to achieve phase matching. The semiconductor multi-wavelength laser device has multiple phase-shifting structures to achieve multi-wavelength lasing output.

3. The semiconductor multi-wavelength laser device according to claim 1, characterized in that: The aforementioned multi-quantum well layer serves as a gain medium covering the wavelength output range of the semiconductor multi-wavelength laser device.

4. A method for fabricating a semiconductor multi-wavelength laser device, characterized in that: The semiconductor multi-wavelength laser device as described in claim 1 is specifically manufactured using the following steps: Step 1: A buffer layer and a lower confinement layer are sequentially grown on the substrate using metal-organic chemical vapor deposition. Then, a multi-quantum-well layer is grown on the lower confinement layer, followed by an upper confinement layer. Finally, a grating layer is grown above the upper confinement layer. Step 2: The grating layer is a laser grating, designed using reconstructed equivalent chirp technology to make the grating period of the laser grating linearly and gradually change. Step 3: Grow InP above the grating layer to bury the grating layer, and then grow the etch barrier layer, waveguide layer and contact layer in sequence.

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