OPS Laser Compound Mirror with Diamond Heat Spreader
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Solution Overview
Problem
Optically pumped, external-cavity surface-emitting semiconductor lasers face thermal roll-off issues due to inadequate heat extraction, particularly with thicker mirror structures and poorly conducting materials at wavelengths longer than 1100 nm or shorter than 900 nm, limiting pump power and efficiency.
Innovation Solution
A gain-module with a multilayer semiconductor gain-structure and a compound mirror-structure that includes a partially reflective and transmissive layer configuration, combined with a diamond heat-spreader, reduces thermal resistance and enhances heat dissipation by distributing heat laterally for improved thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thick mirror-structure is used to achieve high reflectivity at longer wavelengths, then optical performance is improved, but thermal resistance increases and heat extraction becomes inadequate
Solution Approach 1:
The mirror-structure is segmented into two distinct functional layers: a first mirror-layer (AlAs/GaAs) optimized for optical reflectivity and a second mirror-layer (SiO2/Si3N4) optimized for thermal conduction. This segmentation allows each layer to specialize in its respective function without compromising the other, resolving the contradiction between achieving high reflectivity through thickness and maintaining heat extraction capability.
Solution Approach 2:
Different materials are used at different locations within the mirror-structure to optimize local properties. The AlAs/GaAs layers provide high optical reflectivity where needed for laser operation, while the SiO2/Si3N4 layers provide enhanced thermal conduction pathways. This local optimization of material properties allows simultaneous achievement of high reflectivity and improved heat extraction.
2Power
If pump power is increased to increase output power, then laser output increases, but thermal roll-off occurs due to inadequate heat removal
Solution Approach 1:
The second mirror-layer acts as an intermediary thermal conduction pathway between the gain-structure and the heat-sink. This intermediate layer with high thermal conductivity (SiO2/Si3N4) creates additional heat extraction channels that mediate the heat flow, allowing higher pump powers to be applied before thermal roll-off occurs, thereby enabling increased laser output power.
3Adaptability or versatility
If OPS-laser operates at wavelengths longer than 1100 nm or shorter than 900 nm, then wavelength range is extended, but mirror-structure thermal impedance increases
Solution Approach 1:
The dual-layer mirror-structure design provides universal applicability across a broad wavelength range (870-1100 nm and beyond). The first layer handles optical reflection for various wavelengths while the second layer consistently provides thermal management. This multi-functional design allows the same structure to serve both optical and thermal requirements across extended wavelength ranges including fundamental wavelengths longer than 1100 nm or shorter than 900 nm.
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 increases the pump power at which thermal roll-off occurs, enabling efficient operation of OPS-lasers at longer or shorter wavelengths by effectively managing heat extraction and maintaining high reflectivity across the desired wavelength range.
Implementation Method 1
A layer of diamond is bonded to the first mirror... The compound mirror-structure is in thermal communication with a heat-sink... facilitates use of the thicker mirror-structures and poorly conducting semiconductor materials needed for OPS-lasers operating at fundamental wavelengths longer than 1100 nm or shorter than 900 nm
Implementation Method 2
The compound mirror-structure includes a second plurality of layers of material adjacent the gain-structure and is partially reflective and partially transmissive at a fundamental wavelength characteristic of the gain-structure... A third plurality of layers adjacent the layer of diamond is configured such that the compound mirror is highly reflective at the fundamental wavelength
Data Source
AI summary
A gain-module for use in an OPS-laser includes a multilayer semiconductor gain-structure surmounting a multilayer compound mirror-structure. Within the multilayer compound mirror-structure is a relatively thick layer of diamond which serves as a heat-spreader.