High-speed directly-modulated surface emitting laser based on light-light resonance effect

Abstract

The invention provides a high-speed directly-modulated surface emitting laser based on a light-light resonance effect, and relates to the technical field of semiconductor lasers. According to the laser, a light-light resonance effect and a detuning loading effect are introduced, and a composite cavity is formed through an active phase region and a transparent light feedback region which are fed back by an integrated part. The laser is integrated with the L-shaped second-order surface grating, the number of cycles and the waveguide width of the L-shaped second-order surface grating are accurately controlled, near-Gaussian surface emission efficient coupling output is achieved, the PPR effect is generated through optical power feedback of a specific proportion, and the bandwidth of the laser is enhanced. The antenna has the advantages of high bandwidth, surface emission, high temperature stability, high reflection resistance, easiness in integration and the like.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser technology and relates to a high-speed, directly modulated surface-emitting laser based on the optical-optical resonance effect. Background Technology

[0002] With the rapid development of large-scale AI technologies such as ChatGPT and DeepSeek, the global AI training data volume is growing at an average annual rate of 140% (according to Nature Photonics statistics in 2024). This has led to a surge in demand for transmission speeds in data centers and communication networks, simultaneously promoting the development and upgrading of optical communication systems. China has long relied on imports for high-end optical chips, particularly in the market for lasers with speeds above 25 GHz, where the domestic production rate is low. For example, the overall level of directly modulated surface-emitting lasers still lags significantly behind international optical chip standards.

[0003] From the perspective of market demand, with the rapid development of technologies such as artificial intelligence (AI), cloud computing, and 5G / 6G communication, global data traffic has experienced explosive growth, and the demand for high-speed optical communication chips has shown an exponential upward trend. In short-distance optical communication systems, direct-modulation links have become the mainstream solution due to their advantages such as small size, low cost, low power consumption, and ease of array integration. Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in data centers and optical interconnects due to their high speed, low cost, and ease of two-dimensional array integration. However, most existing VCSELs operate in multimode and are coupled with multimode optical fibers, resulting in inaccurate wavelength control, which makes it difficult to meet the requirements of wavelength division multiplexing systems. Currently, the modulation bandwidth of commercial direct-modulation lasers is usually no more than 25 GHz, which has become a key bottleneck in the development of computing networks [1].

[0004] In long-distance transmission scenarios such as metropolitan area networks (MANs) and wide area networks (WANs), long-wavelength VCSELs (operating in the 1310 nm and 1550 nm low-loss, low-dispersion communication windows) can significantly reduce the number of repeater stations and construction costs due to their low mode dispersion and low signal attenuation characteristics, meeting the needs of long-distance data transmission. They can also be integrated into two-dimensional arrays, potentially replacing some high-cost, bulky, and power-intensive electro-absorption modulated lasers (EMLs) and silicon photonic modulators. However, the development of long-wavelength VCSELs faces significant challenges: due to the low refractive index difference of InP-based materials, tens or even hundreds of layers are required to ensure sufficient reflectivity, leading to development difficulties and problems such as limited modulation bandwidth and poor coupling efficiency with single-mode fibers. Furthermore, the performance of high-speed directly modulated semiconductor lasers degrades significantly under high temperature and high reflectivity environments, further limiting their application range.

[0005] Against this backdrop, it is imperative to conduct research on high-temperature resistant and anti-reflection high-bandwidth surface-emitting lasers in order to break through existing technological bottlenecks and achieve independent innovation. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of existing surface-emitting lasers, such as limited modulation bandwidth, poor high-temperature performance, and difficulty in integration and testing of traditional direct-modulation DFB lasers, and to provide a single-mode surface-emitting laser that has high direct-modulation bandwidth, high output efficiency, wide operating temperature range and high anti-reflection characteristics.

[0007] To solve the above-mentioned technical problems, the specific implementation scheme of the present invention is as follows: A quantum dot high-speed direct-modulation surface-emitting laser based on optical-optical resonance effect. The laser has a horizontal cavity structure and integrates a feedback region, a DFB region, an active phase region, and a surface-emitting region sequentially along the light propagation direction. Both the feedback region and the DFB region are etched with first-order gratings, wherein the first-order grating in the feedback region is used to provide optical feedback; the first-order grating in the DFB region is a strip... A first-order grating with a 4 / 4 phase shift is used as the main lasing region, in which The wavelength is denoted by λ. The surface emission region is etched with an L-shaped second-order surface grating to achieve vertical surface emission of the beam and provide partial optical feedback.

[0008] Furthermore, the laser includes a P-back electrode, a substrate, a tunnel junction, a lower waveguide layer, an oxide layer, an active region, and an upper waveguide layer stacked sequentially from bottom to top; A grating is etched at the center of the upper surface of the upper waveguide layer, and from left to right, it consists of the first-order grating, the band... / 4 phase shift first-order grating, gratingless waveguide and L-shaped second-order surface grating; n electrodes are provided on the feedback region, DFB region and active phase region; the n electrodes are located on both sides above the upper waveguide layer and are connected through n contact layers on both sides of the upper waveguide layer.

[0009] Furthermore, the active region is a quantum dot structure or a quantum well gain structure.

[0010] Furthermore, the L-shaped second-order grating not only achieves feedback of a specific power ratio, but also enables directional surface emission output.

[0011] Furthermore, the active phase region is used to adjust the laser phase, and combined with the power feedback function of the L-shaped second-order surface grating, additional modes are introduced into the cavity to form an optical-optical resonance effect.

[0012] Furthermore, the feedback region is used to provide a reflective surface for the laser. By adjusting the position of the reflection spectrum, the laser lasing spectrum is positioned at the falling edge of the reflection spectrum, thereby generating a detuning loading effect to improve the direct modulation bandwidth of the laser.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention innovatively applies the PPR and DL effects to a surface-emitting laser by integrating a composite cavity structure, breaking through the intrinsic bandwidth limitation of traditional surface-emitting lasers and significantly improving the direct-modulation bandwidth. This invention uses quantum dot materials as the active region, utilizing their… The functional state density distribution yields low threshold current, high differential gain, wide operating temperature range, and high anti-reflection characteristics. This invention employs a unique L-shaped second-order surface grating instead of a traditional uniform grating, achieving highly efficient directional surface emission output with an upward output ratio significantly exceeding 50%, and the output beam is near-Gaussian in shape, facilitating coupling with single-mode fibers. The laser solution of this invention offers numerous advantages, including high bandwidth, high-efficiency output, high temperature stability, convenient detection, high anti-reflection properties, and ease of integration. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the laser of the present invention.

[0015] Figure 2 This is a schematic diagram of the cross-sectional structure of the laser of the present invention.

[0016] Figure 3 This is an isometric view of the laser of the present invention.

[0017] In the diagram: 11. First-order grating; 12. Band / 4 Phase-shifted first-order grating, 13. Gratingless waveguide, 14. L-type second-order surface grating, 1. n-electrode, 2. n-contact layer, 3. Upper waveguide layer, 4. Active region, 5. Oxide layer, 6. Lower waveguide layer, 7. Tunnel junction, 8. Substrate, 9. P-back electrode. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Below is a high-speed, directly modulated surface-emitting laser based on the optical-optical resonance effect of this invention. A schematic diagram of the laser is shown below. Figure 1 As shown, the cross-sectional view is as follows Figure 2 As shown.

[0020] Compared with the traditional uniform second-order grating, the L-shaped second-order surface grating 14 of this invention achieves efficient directional output by generating constructive interference in the forward diffraction direction and destructive interference in the undesired direction through its asymmetric structure.

[0021] A schematic diagram of the cross-sectional structure of the laser is shown below. Figure 2 As shown, its layered structure includes, from top to bottom, an n-electrode 1, an n-contact layer 2, an upper waveguide layer 3, an active region 4, an oxide layer 5, a lower waveguide layer 6, a tunnel junction 7, a substrate 8, and a P-back electrode 9.

[0022] Among them, electrode 1 is used to form an ohmic contact and inject current.

[0023] The n-contact layer 2 is a highly doped GaAs layer, used to achieve good current spread.

[0024] The upper waveguide layer 3 is made of GaAs material, and together with the lower waveguide layer 6, it confines the optical field to the vicinity of the active region 4. In addition, in order not to introduce additional absorption losses, the electrodes need to be kept a distance of several micrometers from the optical waveguide, i.e., a lateral current injection method is used.

[0025] The active region 4 is the core gain region of this invention. It adopts a multi-layer quantum dot structure or a quantum well and other gain structures to provide the laser with high differential gain, low threshold current and wide temperature operating characteristics.

[0026] The oxide layer 5 is formed by selective wet oxidation of the p-AlGaAs layer. The unoxidized window in the center is used to precisely limit the current injection path, effectively reducing leakage current, improving laser current injection efficiency and reducing device capacitance.

[0027] In order to improve the intrinsic modulation bandwidth of the laser, reduce heat accumulation, and reduce the laser's sensitivity to external reflections, the lower waveguide layer 6 can use a multi-layer quantum dot active region to provide gain for the laser.

[0028] Tunnel junction 7 is used to achieve efficient carrier regeneration and injection in nip-doped structures.

[0029] Substrate 8 is typically a GaAs or silicon-based substrate.

[0030] This laser employs a lateral current injection method, with current injected from the top n-electrode 1, flowing laterally through the n-contact layer 2 and the upper waveguide layer 3, vertically through the window of the active region 4 and the oxide layer 5, and finally reaching the p-back electrode 9 through the tunnel junction 7 and the substrate 8 to complete the circuit. This nip-doped structure combined with lateral oxide confinement significantly improves current injection efficiency and modulation response speed while ensuring the effective interaction between the optical field and the surface grating.

[0031] This embodiment uses a 7-layer InAs / GaAs quantum dot structure with active region 4 operating in the 1310 nm communication band as an example. The cross-section shows the thin top cap layer, surface grating, lateral injection electrode, and oxide layer for current confinement. This structure ensures both strong coupling between the grating and the optical field and achieves efficient current injection.

[0032] The horizontal cavity laser sequentially integrates a feedback region, a DFB region, an active phase region, and a surface-emitting region along the light propagation direction; the feedback region is etched with a first-order grating 11 to provide optical feedback; the DFB region is etched with a band... A first-order grating 12 with a phase shift of 4 / 4 serves as the main lasing region of the laser; the active phase region is a gratingless waveguide 13, used for optical amplification and phase modulation, forming a composite cavity with the feedback region to excite optical-optical resonance and detuning loading effects; the surface emission region is etched with an L-shaped second-order surface grating 14, used to realize vertical surface emission output of the beam and provide partial optical feedback.

[0033] The laser employs a current injection method combining lateral current injection and lateral oxidation confinement. The etching parameters of the L-shaped second-order surface grating 14 are optimized to achieve an upward-oriented output efficiency far exceeding 50%, forming a near-Gaussian distributed output beam. By adjusting the length of the active phase region and the injection current, and optimizing the detuning of the reflection spectrum of the feedback region relative to the lasing wavelength, the optical-optical resonance effect and the detuning loading effect can be synergistically controlled.

[0034] This invention designs an L-shaped second-order surface grating 14. This structure can be fabricated using simple stacked photolithography and dry etching steps, avoiding complex tilting etching or multi-layer deposition processes. The vertical grating coupler allows constructive interference of light waves in the forward diffraction direction and destructive interference in the undesired diffraction direction, effectively increasing the proportion of forward diffracted light.

[0035] In summary, this invention proposes a high-speed, directly modulated surface-emitting laser based on the PPR effect. Through the synergistic innovation of quantum dot materials, composite cavity mechanisms, and L-shaped second-order surface grating 14 structures, it successfully solves the industry challenge of simultaneously achieving high bandwidth, surface emission, high-temperature stability, and high integration, providing an ideal light source solution for next-generation high-speed optical communication networks.

[0036] Based on the design and operating principles of the present invention, those skilled in the art can fully understand that the specific parameters are merely illustrative examples and do not specifically limit the mode selection method or the material, shape, position, number of periods, and duty cycle of the grating.

[0037] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-speed, directly modulated surface-emitting laser based on optical-optical resonance effect, characterized in that, The laser has a horizontal cavity structure, and along the light propagation direction, it integrates a feedback region, a DFB region, an active phase region, and a surface emission region in sequence. Both the feedback region and the DFB region are etched with first-order gratings (11), wherein the first-order grating in the feedback region is used to provide optical feedback; the first-order grating in the DFB region is a strip A first-order grating (12) with a phase shift of 4 / 4 is used as the main lasing region, in which The wavelength is denoted by λ; an L-shaped second-order surface grating (14) is etched on the surface emission region to realize vertical surface emission output of the beam and provide partial optical feedback.

2. The high-speed, directly modulated surface-emitting laser based on the optical-optical resonance effect according to claim 1, characterized in that, The laser comprises, from bottom to top, a P-back electrode (9), a substrate (8), a tunnel junction (7), a lower waveguide layer (6), an oxide layer (5), an active region (4), and an upper waveguide layer (3). A grating is etched at the middle position of the upper surface of the upper waveguide layer (3), and from left to right, it consists of the first-order grating (11), the band... / 4 phase shift first-order grating (12), gratingless waveguide (13) and L-type second-order surface grating (14); n electrodes (1) are provided on the feedback region, DFB region and active phase region; the n electrodes (1) are located on both sides above the upper waveguide layer (3) and are connected by n contact layers (2) on both sides of the upper waveguide layer (3).

3. A high-speed, directly modulated surface-emitting laser based on optical-optical resonance effect according to claim 2, characterized in that, The active region (4) is a quantum dot structure or a quantum well gain structure.

4. A high-speed, directly modulated surface-emitting laser based on optical-optical resonance effect according to claim 2, characterized in that, The L-shaped second-order surface grating (14) is used to achieve feedback and directional surface emission output with a specific power ratio.

5. A high-speed, directly modulated surface-emitting laser based on optical-optical resonance effect according to claim 2, characterized in that, The active phase region is used to adjust the laser phase. Combined with the power feedback function of the L-shaped second-order surface grating (14), an additional mode is introduced into the cavity to form an optical-optical resonance effect.

6. A high-speed, directly modulated surface-emitting laser based on optical-optical resonance effect according to claim 2, characterized in that, The feedback region is used to provide a reflective surface for the laser. By adjusting the position of the reflection spectrum, the laser lasing spectrum is positioned at the falling edge of the reflection spectrum, thereby generating a detuning loading effect to improve the direct modulation bandwidth of the laser.

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