VCSEL Thermal Management via Segmented DBR Layers
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Solution Overview
Problem
Vertical cavity surface emitting lasers (VCSELs) face challenges with thermal management due to their small active layer volume, leading to significant temperature increases and limited optical power compared to edge emitting semiconductor lasers, which affects their performance in applications like optical communication and image forming.
Innovation Solution
The VCSEL design incorporates a substrate with a first and second semiconductor multilayer reflector, where at least one pair of layers in each reflector has a lower thermal resistance with an optical thickness greater than ¼ of the oscillation wavelength and a higher thermal resistance with an optical thickness less than ¼ of the oscillation wavelength, optimized to enhance heat dissipation and maintain high reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the active layer volume is increased to improve optical power, then optical power increases, but the VCSEL structure becomes more complex and fabrication difficulty increases
Solution Approach 1:
The patent segments the DBR mirror structure into multiple functional layers with different thermal resistances. The lower DBR includes a first low-thermal-resistance layer and a second high-thermal-resistance layer, creating a segmented thermal management system that improves heat dissipation without increasing active layer volume or overall device complexity
Solution Approach 2:
The patent applies local quality by assigning different thermal resistance characteristics to different layers within the DBR structure. Specifically, the first layer has lower thermal resistance for heat dissipation, while the second layer has higher thermal resistance, creating localized thermal management zones that optimize both heat dissipation and optical performance
2Power
If current injection is increased to improve optical power, then optical power increases, but temperature increase in the active layer worsens
Solution Approach 1:
The patent introduces an intermediary thermal management layer between the active layer and the substrate. The first layer with lower thermal resistance acts as a thermal conduit, facilitating heat transfer from the active layer to the substrate, thereby mediating the thermal relationship and preventing excessive temperature rise in the active layer during high-power operation
Solution Approach 2:
The patent changes the thermal resistance parameter of the DBR layers to optimize heat dissipation. By selecting materials and thicknesses that provide lower thermal resistance in the first layer, the structure enables more efficient heat removal, allowing the VCSEL to operate at higher optical powers without excessive temperature increase
3Reliability
If DBR mirror reflectance is increased to improve laser performance, then optical performance improves, but thermal resistance increases
Solution Approach 1:
The patent applies local quality by differentiating the thermal properties of different DBR layers. The first layer is designed with lower thermal resistance for heat dissipation, while the second layer has higher thermal resistance, allowing each layer to perform its specialized function - maintaining high reflectance while managing thermal load
Solution Approach 2:
The patent uses composite materials in the DBR structure, combining layers with different thermal and optical properties. The first layer uses materials with lower thermal resistance, while the second layer uses materials with higher thermal resistance, creating a composite structure that achieves both high reflectance and improved thermal management
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
This configuration effectively reduces thermal resistance, increases optical power, and maintains high reflectance, enabling high-speed optical communication, image forming, and scanning applications with improved reliability and efficiency.
Implementation Method 1
at least one pair of layers of the first semiconductor multilayer reflector and/or the second semiconductor multilayer reflector includes a first layer with a lower thermal resistance that has an optical thickness greater than 1/4 of the oscillation wavelength and a second layer with a higher thermal resistance that has an optical thickness less than 1/4 of the oscillation wavelength
Implementation Method 2
the optical power, optical spectrum, mode, and service life of a semiconductor laser are affected by the degree of thermal diffusion resulting from current injection
Implementation Method 3
a first semiconductor multilayer reflector including plural pairs of layers having differing refractive indexes and thermal resistances, a resonator region including an active layer, and a second semiconductor multilayer reflector including plural pairs of layers having differing refractive indexes and thermal resistances
Implementation Method 4
a bottom DBR made of AlGaAs material, wherein AlAs, which has the lowest thermal resistance among AlGaAs materials, is used as a lower refractive index layer making up a large portion of the lower side of the bottom DBR
Data Source
AI summary
A vertical cavity surface emitting laser element is provided that includes a substrate, a first semiconductor multilayer reflector including plural pairs of layers having differing refractive indexes and thermal resistances, a resonator region including an active layer, and a second semiconductor multilayer reflector including plural pairs of layers having differing refractive indexes and thermal resistances.