Surface-Emitting Laser Array Stress-Adjustment Unit
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Solution Overview
Problem
Existing arrays of surface-emitting lasers face challenges in achieving single-mode operation with low driving current while maintaining a compact size, as prior solutions either fail to improve multimode performance or increase device volume to reduce divergence angles.
Innovation Solution
An array of surface-emitting lasers with a stress-adjustment unit comprising a copper layer and epitaxial device units, including a first and second distributed Bragg reflector, a current-confining aperture, and a diffusion unit, which allows for stress adjustment to single-polarize the laser mode without increasing driving current, thereby reducing volume and minimizing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a back lens is added to reduce far-field divergence angle, then the laser beam quality is improved, but the device volume becomes large
Solution Approach 1:
The patent extracts the beam quality control function from external optical components (back lens) and integrates it into the laser cavity structure itself through the diffusion unit and DBR design, eliminating the need for separate volume-consuming optical elements
Solution Approach 2:
The patent controls far-field divergence by manipulating the vertical cavity structure (second DBR with diffusion unit) rather than adding horizontal optical components, effectively using the vertical dimension to achieve beam quality improvement without increasing lateral device volume
2Power
If multimode operation is used to increase power output, then the laser power is improved, but the far-field divergence angle increases
Solution Approach 1:
The patent creates different functional zones within the active region through the diffusion unit, where the annular area has different optical properties than the central area, enabling mode selection and single-mode operation while maintaining high power output capability
Solution Approach 2:
The patent changes the optical parameters of the second DBR by creating a diffusion unit with reduced thickness (0.1-2 micrometers) and selective compositional disordering, which modifies the reflectivity spectrum to support only fundamental mode operation, thereby achieving low divergence angle with high power capability
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 solution enables high-brightness unipolar output with a narrow divergent angle, achieving clear and high-resolution images suitable for face recognition applications with enhanced security.
Implementation Method 1
single-polarize with stress adjustment provided by a stress-adjustment unit for enhancing the selection of laser mode
Implementation Method 2
The current-confining aperture obtains a current confinement zone through oxidation or indentation at an annular lateral part of an aluminum (Al) composite layer
Implementation Method 3
the diffusion unit is located around an annular area on top of the second DBR with a multilayer of different compositions selectively disordered through a doping diffusion process
Implementation Method 4
a first distributed Bragg reflector (DBR); an active region stacked on the first DBR; and a second DBR stacked on the active region
Data Source
AI summary
An array of surface-emitting lasers is provided. The array outputs high brightness in a unipolar way. The array comprises a stress-adjustment unit and a plurality of epitaxial device units. The stress-adjustment unit is used to adjust stress. The stress from a substrate is used to select a laser mode for an aperture unit. The selection of the laser mode is enhanced for the aperture unit without sacrificing driving current. Low current operation is achieved in a single mode for effectively reducing volume and further minimizing the size of the whole array to achieve high-quality laser output. An object can be scanned by the outputted laser to obtain a clear image with a high resolution. Hence, the present invention is applicable for face recognition with high recognition and high security.