1550 nm VCSEL Bragg Reflector with Fewer High-Reflectance Layers
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Solution Overview
Problem
Conventional distributed Bragg reflectors for vertical-cavity surface-emitting lasers require a complex structure and complicated manufacturing process to achieve the necessary reflectance, particularly for the top and bottom reflectors, which are not efficiently addressed by existing methods.
Innovation Solution
A method involving the formation of silicon and silicon dioxide layers alternately stacked on a substrate using nano-sputtering and micro-plasma oxidation, with a reflective metal layer, to enhance the reflectance of the Bragg reflector to 99.9% for the bottom reflector and 98% for the top reflector, reducing the number of layers required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor materials are used to form distributed Bragg reflector, then high reflectance (99.9% for bottom, 96% for top) can be achieved, but the structure becomes extremely complex requiring about 60 layers of semiconductor film
Solution Approach 1:
The patent uses composite materials consisting of silicon layers and silicon dioxide layers alternately stacked to form the distributed Bragg reflector. This composite structure achieves the required high reflectance (99.9% for bottom DBR, 96% for top DBR) with significantly fewer layers compared to conventional semiconductor materials, thereby reducing structural complexity while maintaining optical performance
Solution Approach 2:
The patent changes the material parameters by using silicon and silicon dioxide with specific refractive index differences instead of conventional semiconductor materials. By optimizing the thickness and alternation of these layers, the reflectance parameter is maximized while the number of layers is minimized, resolving the contradiction between high reflectance and structural complexity
2Reliability
If conventional MOCVD process is used to form semiconductor film for distributed Bragg reflector, then high reflectance can be achieved, but the manufacturing process becomes extremely complicated
Solution Approach 1:
The patent changes the manufacturing process parameters by using physical vapor deposition (sputtering) and plasma oxidation instead of chemical vapor deposition (MOCVD). This process substitution simplifies the manufacturing procedure while achieving the same high reflectance performance, as evidenced by the successful formation of silicon and silicon dioxide layers with controlled thickness and composition
Solution Approach 2:
The patent replaces the chemical-based MOCVD process with a combination of physical sputtering and plasma oxidation processes. This substitution simplifies the manufacturing complexity by using more straightforward physical deposition and oxidation methods that are easier to control and implement for forming the silicon-based DBR structure
3Reliability
If about 60 layers of semiconductor film are stacked to achieve high reflectance, then basic physical/optical requirements for forming resonant laser are improved, but the manufacturing time and process complexity increase significantly
Solution Approach 1:
The patent uses composite silicon and silicon dioxide layers that provide superior optical contrast due to their different refractive indices. This allows achieving the required optical performance for resonant laser formation with far fewer layers than conventional semiconductor materials, thereby significantly reducing the stacking time and manufacturing complexity
Solution Approach 2:
The patent optimizes the layer parameters by using silicon and silicon dioxide with optimized thickness values that maximize the optical path difference and reflectance. This parameter optimization enables achieving high reflectance with minimal layer count, reducing both manufacturing time and process complexity while maintaining the optical performance required for laser resonance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves high reflectance with a simpler structure, improving light-emitting efficiency and reducing manufacturing complexity, making it suitable for applications like automotive radar and LiDAR.
Implementation Method 1
forming silicon layers and silicon dioxide layers that are alternately stacked to each other on the silver layer. The silicon dioxide layers are formed by a process of nano-sputtering and micro-plasma oxidation
Implementation Method 2
forming silicon layers and silicon dioxide layers that are alternately stacked to each other on the silver layer. The silicon dioxide layers are formed by a process of nano-sputtering and micro-plasma oxidation
Implementation Method 3
by way of metal-organic chemical vapor deposition (MOCVD), semiconductor materials of different refractive indexes are alternately stacked onto a substrate to form a semiconductor film, so that a distributed Bragg reflector can be formed. Further, through a selection of materials and a thickness design, an effect of reflecting light of a specific wavelength can be achieved
Data Source
AI summary
A method for manufacturing a distributed Bragg reflector. The distributed Bragg reflector is applied to a 1550 nm vertical-cavity surface-emitting laser, which structurally includes a top distributed Bragg reflector, a bottom distributed Bragg reflector, and a vertical cavity (including a P-type and an N-type electrode) and a multiple quantum well light-emitting layer that are positioned therebetween. An optical multilayer film of the distributed Bragg reflector is formed by sputtering, and includes silicon layers and silicon dioxide layers alternately stacked to each other. The silicon dioxide layers are produced by a process of nano-sputtering and micro-plasma oxidation. A reflectance of the bottom distributed Bragg reflector at 1,550 nm is greater than 99.9%, and a reflectance of the top distributed Bragg reflector at 1,550 nm is controlled to be between 95% and 99%, so that basic physical/optical requirements for forming a resonant laser can be improved.