Silicon-based external cavity laser based on vertical gain cavity
The silicon-based external cavity laser with a vertical gain cavity structure addresses the challenges of narrow linewidth and cost by integrating a vertical emission chip with a silicon-based external cavity, achieving high-power output and simplified manufacturing while enabling system integration.
Patent Information
- Application Number
- CN202510446040.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-15
AI Technical Summary
In the prior art, the integration process of a single-chip integrated laser is difficult, the feedback control is complex and the cost is high, the coupling loss of the outer cavity laser is high, and the process tolerance is poor, making it difficult to achieve the laser requirements of narrow line width and low cost.
A silicon-based external cavity laser based on a vertical gain cavity is adopted. The vertical emission chip is end-to-end coupling or lens coupling between the silicon-based external cavity chip, combined with a high Q band pass light feedback mechanism, and a single-mode operation and narrow line width are achieved, reducing process difficulty and cost.
It realizes the single-mode working conditions of the laser, improves output power, reduces production costs, has high process tolerance and low cost technical effects, and supports monolithic integration or heterogeneous integration with silicon-based optoelectronic chips to improve system integration.
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Figure CN120320156A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of semiconductor lasers, and particularly relates to a silicon-based external cavity laser based on a vertical gain cavity. Background Art
[0002] For applications such as short-distance data center communication, ultra-high bandwidth optical interconnection, and coherent optical communication, many characteristic index requirements such as narrow linewidth, small volume, and low cost are put forward for lasers. At present, the technical solutions of high-performance lasers are mainly divided into two categories: monolithic integration type and external cavity type.
[0003] In the monolithic integration type, a mirror, a filtering structure, and a gain region are all integrated together through secondary epitaxy. The integration process of this type of laser is difficult, the feedback control is relatively complex, resulting in high costs, and the linewidth performance is poor.
[0004] In traditional external cavity lasers, the gain region and the mode selection structure are separated into independent components, and laser output is achieved through a coupling and packaging method. This form of coupling and packaging has high coupling loss and poor process tolerance. Summary of the Invention
[0005] The purpose of the present invention is to propose a silicon-based external cavity laser based on a vertical gain cavity in view of the problems existing in the background art, aiming to achieve the single-mode working condition of the laser while improving the output power and narrow linewidth, and reducing the process difficulty and manufacturing cost of such lasers.
[0006] To achieve the above object, the technical solution adopted by the present invention is: a silicon-based external cavity laser based on a vertical gain cavity, comprising a vertical emission chip and a silicon-based external cavity chip;
[0007] The vertical emission chip includes a mirror, an upper cladding layer, a quantum well region, a lower cladding layer, and a contact layer connected in sequence, wherein the contact layer is connected to the silicon-based external cavity chip, and after the quantum well region emits light, the light is vertically fed back to the silicon-based external cavity chip through the mirror;
[0008] The silicon-based external cavity chip includes a cover layer, a core layer, a box layer, and a substrate connected in sequence from top to bottom. A coupler, a phase modulation region, a light reflector, and an output region are installed on the core layer. The coupler is coupled to the vertical emission chip and is connected to the phase modulation region, the light reflector, and the output region through a waveguide in sequence, and the output region is used as the laser output port.
[0009] Further, the connection method between the vertical emission chip and the silicon-based external cavity chip includes: fixing the vertical emission chip on the silicon-based external cavity chip through the contact layer, erecting the vertical emission chip, and directly realizing coupling with the silicon-based external cavity chip through end-to-end coupling or lens coupling;
[0010] Among them, when the vertical emission chip is mounted on the silicon-based external cavity chip, the coupling methods between the coupler and the vertical emission chip include end-face coupling, evanescent wave, grating coupling, lens coupling, flip-chip packaging or wafer bonding.
[0011] Furthermore, when the vertical emission chip is mounted on the silicon-based external cavity chip, it also includes a 45-degree rotation of the end face of the silicon-based external cavity chip to directly transfer the light of the chip waveguide to the vertical emission chip. The forms of the 45-degree rotation include 45-degree polishing of the end face of the silicon-based external cavity chip, pasting a 45-degree turning prism or 45-degree lens coupling on the end face of the silicon-based external cavity chip.
[0012] Furthermore, the optical reflector has a high-Q bandpass effect, performs mode selection on the longitudinal mode of the laser and realizes optical feedback, forms a laser resonator together with the mirror of the vertical emission chip, and realizes single-wavelength operation.
[0013] Furthermore, the optical reflector includes a Sagnac mirror, a Bragg mirror or a photonic crystal.
[0014] Furthermore, the vertical emission chip is a vertical cavity FP laser, which is realized by adding a mirror, conventional growth of III-V materials or coating between the contact layer and the lower cladding; then a single mode is formed through the silicon-based external cavity.
[0015] Furthermore, a tunable grating or a tunable microring resonator is also integrated on the silicon-based external cavity chip to control the optical wavelength in the resonator formed by the mirror and the optical reflector to meet the resonance condition and realize the tuning of the laser.
[0016] Furthermore, the material of the silicon-based external cavity chip is SOI, SiN, SiON, SiO2 or lithium niobate material.
[0017] Advantages of the present invention:
[0018] The vertical emission chip has the characteristic of a large emission surface. It can not only achieve high-power output, but also be easily coupled with the silicon-based chip. The process is simple and has extremely high process tolerance; the silicon-based external cavity chip is realized by on-chip integration through the SOI, SiN, SiON, SiO2 or lithium niobate material process platform of the silicon substrate, achieving the technical effect of small size; whether it is a silicon optical chip or a vertical emission chip, they are both widely used commercial technology platforms at present, and the prices are very low, having the technical effect of low cost; the mode selection of the laser is realized by designing an optical feedback mechanism with high-Q bandpass performance, and the wavelength coverage range is wide, achieving the single-mode and narrow linewidth technical effects of an external cavity laser. In addition, the silicon-based external cavity laser can further realize monolithic integration with the silicon-based optoelectronic chip or heterogeneous integration with other chips, greatly improving the integration degree of the system. Description of the Drawings
[0019] Figure 1 is a schematic cross-sectional structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 1 of the present invention;
[0020] Figure 2 is a schematic top view structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 1 of the present invention;
[0021] Figure 3 is a curve showing the variation of the calculated linewidth and longitudinal mode spacing with the equivalent cavity length according to Embodiment 1 of the present invention;
[0022] Figure 4 is a schematic cross-sectional structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 2 of the present invention;
[0023] Figure 5 is a schematic cross-sectional structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 3 of the present invention;
[0024] Figure 6 is a schematic top view structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 4 of the present invention;
[0025] Figure 7 is a schematic top view structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 5 of the present invention.
[0026] Figure 8 is a schematic top view structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 6 of the present invention. Detailed Embodiments
[0027] The following further details the specific embodiments of the present invention with reference to the accompanying drawings.
[0028] A silicon-based external cavity laser based on a vertical gain cavity includes a vertical emission chip 1 and a silicon-based external cavity chip 2; the vertical emission chip includes a reflector 10, an upper cladding layer 11, a quantum well region 12, a lower cladding layer 13 and a contact layer 14, wherein the contact layer 14 is connected to the silicon-based external cavity chip 2; the silicon-based external cavity chip 2 is composed of a cover layer 211, a core layer 212, a box layer 213 and a substrate 214, and corresponding devices need to be fabricated on the core layer 212 to achieve functions, including a coupler 221, a phase modulation region 222, an optical reflector 223 and an output region 224; the coupler 221 is used to connect the vertical emission chip 1 and the silicon-based external cavity chip 2, and is connected to the phase modulation region 222, the optical reflector 223 and the output region 224 in sequence through a waveguide, and the output region 224 is used as the laser output port;
[0029] Embodiment 1: Figure 1 is a schematic cross-sectional structure diagram of a silicon-based external cavity laser based on a vertical gain cavity according to Embodiment 1 of the present invention. Refer toFigure 1 , the fast wavelength tunable laser includes: a vertical emission chip 1, a coupler 221, a phase modulation region 222, an optical reflector 223, and an output region 224.
[0030] The quantum well region 12 of the vertical emission chip 1 provides population inversion for the laser by applying current to provide gain. The upper cladding layer 11 and the lower cladding layer 13 provide optical confinement. The reflector 10 has a reflectivity of 100%, and feeds the light back to the contact layer 14, making the light emit perpendicularly to the chip surface. The light of the vertical emission chip 1 is transmitted to the silicon-based external cavity chip 2 through the contact layer 14.
[0031] The reflector 10 includes a Bragg reflector and a metal electrode reflector.
[0032] The contact layer 14 is used to fix the vertical emission chip 1 on the silicon-based external cavity chip 2. The fixing method can be flipchip metal bonding, wafer bonding, or lens coupling.
[0033] Figure 2 It is a top view structural schematic diagram of a silicon-based external cavity laser based on a vertical gain cavity in the first embodiment of the present invention. The coupler 221, the phase modulation region 222, the optical reflector 223, and the output region 224 are integrated on the silicon optical chip. The core layer material of the optical transmission waveguide is SOI, SiN, SiON, SiO2, or lithium niobate material.
[0034] The coupler 221 realizes the optical coupling between the vertical emission chip 1 and the silicon-based external cavity chip 2. The coupling methods include end face coupling, evanescent wave, grating coupling, lens coupling, flip-chip packaging, and wafer bonding.
[0035] The phase region 222 can adjust the phase of the light through a thermal control or an electrical control mechanism, and is used to control the light wavelength in the resonant cavity formed by the reflector 10 and the optical reflector 223 to satisfy the resonance condition, that is, to make the phase of the light be an integer multiple of 2π when it travels back and forth in the optical resonant cavity, so as to laser at the corresponding wavelength, as shown in the formula: That is, 2nL = mλ, and the formed longitudinal mode interval is where n is the equivalent refractive index in the cavity, L is the equivalent cavity length of the laser, m is the order, and λ is the lasing wavelength.
[0036] The optical reflector 223 is a band-pass reflector with a high Q band-pass effect, which selects the mode of the longitudinal mode of the laser and realizes optical feedback, and forms a laser resonant cavity together with the reflector of the vertical emission chip to achieve single wavelength operation, including a Sagnac reflector, a Bragg reflector, and a photonic crystal.
[0037] The output region 224 serves as the output port of the laser, and the output methods include end face output, grating surface output, and lens coupling output.
[0038] Traditional vertical-emitting chips are multimode. By designing an optical feedback mechanism with high-Q bandpass performance to select a mode for the laser, a controllable single mode can be achieved. Due to material limitations, it is very difficult to fabricate lasers in the C band for traditional vertical-emitting chips, and the process is complex. The vertical-emitting chip of the present invention only provides gain, which can avoid these materials and theoretically can cover all designable wavelengths, with a wide wavelength coverage range.
[0039] Linewidth is a very important parameter of a laser. The smaller the linewidth, the smaller the phase noise, which is extremely important for coherent detection. As shown in the above laser resonance conditions, due to the very long equivalent cavity length of the laser, the longitudinal mode spacing is very small, and at the same time the linewidth is continuously reduced. For example Figure 3 is the curve of the linewidth and longitudinal mode spacing calculated in this example as a function of the equivalent cavity length. When the equivalent cavity length reaches 10 mm, the linewidth reaches 20 kHz, which is one order of magnitude smaller than that of commercial monolithic integrated narrow-linewidth lasers. At the same time, the longitudinal mode spacing is 0.015 nm. In order to achieve single longitudinal mode operation, its spectral width must be less than the above longitudinal mode spacing. For example, a common optical reflector is a Bragg reflector, and its spectral width is about where Λ is the half wavelength. The Bragg reflector needs to be designed as a low-reflectivity grating, which is very easy to achieve in a silicon photonics chip. At the silicon photonics process node, the wavelength range that can be covered by the designed mirrors is very wide.
[0040] Power is another important parameter of a laser. Its emission power is proportional to the volume of the entire active quantum well. Whether it is a monolithic integrated laser or a traditional silicon photonics external cavity laser, in order to achieve a high power output of 100 mW, the typical size of the optical gain chip part is usually 500 um * 1800 um = 9e5 um^2. However, for the technical solution of this article, due to the use of a vertical-emitting chip, it has a higher light-emitting area. For example, the current size that can achieve a high power output of 300 mW is 300 um * 300 um = 9e4 um^2, that is, the light-emitting power is higher under a smaller active area size. If a multi-layer quantum well, multi-junction quantum well or array vertical structure is used, the power can be further improved.
[0041] Embodiment 2
[0042] As Figure 4 shown, it is a cross-sectional schematic diagram of Embodiment 2 of the present invention. The end face of the silicon-based external cavity chip is turned by 45 degrees to directly transfer the light of the chip waveguide to the vertical-emitting chip 1. The forms of the 45-degree turn include grinding and polishing the end face of the silicon-based external cavity chip by 45 degrees, pasting a 45-degree turning prism on the end face of the silicon-based external cavity chip, and 45-degree lens coupling.
[0043] Embodiment 3
[0044] AsFigure 5 As shown, it is a cross-sectional schematic diagram of the third embodiment of the present invention. The vertical-emitting chip 1 is erected and directly coupled end-to-end with the silicon-based external cavity chip, or coupled through a lens.
[0045] Embodiment 4
[0046] As Figure 6 shown, it is a cross-sectional schematic diagram of the fourth embodiment of the present invention. The vertical-emitting chip can be a vertical-cavity FP laser. For example, a layer of mirror 10 can be added between the contact layer 14 and the lower cladding layer 13 of the vertical-emitting chip, which can be a traditional III-V material grown or formed by coating. The vertical-cavity FP laser emits a series of longitudinal modes, and then the silicon-based external cavity is used to select the modes. The effect is that the threshold of the single-mode laser is greatly reduced.
[0047] Embodiment 5
[0048] As Figure 7 shown, it is a top view schematic diagram of the fifth embodiment of the present invention. An optical resonator, including a micro-ring resonator, a Bragg reflector or an optical etalon, is introduced at the output end to form an injection-locking structure, further improving the linewidth performance of the laser; the order of the various structures included in the silicon-based external cavity chip can be swapped.
[0049] Embodiment 6
[0050] As Figure 8 shown, it is a top view schematic diagram of the sixth embodiment of the present invention. A tunable grating or a tunable micro-ring resonator is integrated on the silicon-based external cavity chip to realize a silicon-based external cavity broadband tunable narrow linewidth laser.
[0051] Optionally, the silicon-based external cavity laser can further be monolithically integrated with the silicon-based optoelectronic chip or heterogeneously integrated with other chips, greatly improving the integration of the system.
[0052] Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the content disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of the present application are pointed out by the claims.
[0053] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. The present application is not limited to the precise structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present application is only limited by the appended claims.
Claims
1. A silicon-based external cavity laser based on a vertical gain cavity, characterized in that, It includes a vertical emission chip and a silicon-based external cavity chip; The vertical emission chip includes a reflector, an upper cladding layer, a quantum well region, a lower cladding layer, and a contact layer connected in sequence, where the contact layer is connected to the silicon-based external cavity chip, and after the quantum well region emits light, the light is vertically fed back to the silicon-based external cavity chip through the reflector; The silicon-based external cavity chip is composed of a covering layer, a core layer, a box layer, and a substrate connected in sequence from top to bottom. A coupler, a phase modulation region, a light reflector, and an output region are installed on the core layer. The coupler is coupled with the vertical emission chip and is connected to the phase modulation region, the light reflector, and the output region through a waveguide in sequence, and the output region serves as the laser output port.
2. The silicon-based external cavity laser based on a vertical gain cavity according to claim 1, wherein The connection method between the vertical emission chip and the silicon-based external cavity chip includes: fixing the vertical emission chip on the silicon-based external cavity chip through the contact layer, erecting the vertical emission chip, and directly realizing coupling with the silicon-based external cavity chip through end-to-end coupling or lens coupling; Among them, when the vertical emission chip is installed on the silicon-based external cavity chip, the coupling method between the coupler and the vertical emission chip includes end-face coupling, evanescent wave, grating coupling, lens coupling, flip-chip packaging, or wafer bonding method.
3. The silicon-based external cavity laser based on a vertical gain cavity according to claim 2, wherein When the vertical emission chip is installed on the silicon-based external cavity chip, it also includes a 45-degree rotation of the end face of the silicon-based external cavity chip to directly transfer the light of the chip waveguide to the vertical emission chip. The form of the 45-degree rotation includes grinding and polishing the end face of the silicon-based external cavity chip at 45 degrees, pasting a 45-degree corner prism or a 45-degree lens coupling on the end face of the silicon-based external cavity chip.
4. The silicon-based external cavity laser based on a vertical gain cavity according to claim 1, wherein The light reflector has a high-Q bandpass effect, selects the mode of the laser longitudinal mode and realizes optical feedback, forms a laser resonant cavity together with the reflector of the vertical emission chip, and realizes single-wavelength operation.
5. A silicon-based external cavity laser based on a vertical gain cavity according to claim 1, characterized in that, The light reflector includes a Sagnac reflector, a Bragg reflector, or a photonic crystal.
6. The silicon-based external cavity laser based on a vertical gain cavity according to claim 1, wherein The vertical emission chip is a vertical cavity FP laser, which is realized by adding a reflector, traditional III-V material growth or coating between the contact layer and the lower cladding layer; then a single mode is formed through the silicon-based external cavity.
7. The silicon-based external cavity laser based on a vertical gain cavity according to claim 1, wherein An adjustable grating or an adjustable microring resonator is also integrated on the silicon-based external cavity chip to control the light wavelength in the resonant cavity formed by the reflector and the light reflector to meet the resonant condition and realize the tuning of the laser.
8. The silicon-based external cavity laser based on a vertical gain cavity according to claim 1, wherein The material of the silicon-based external cavity chip is SOI, SiN, SiON, SiO2, or lithium niobate material.