Laser Diode Thermal Aperture for Reduced Thermal Lensing
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Solution Overview
Problem
Broad-area diode lasers experience significant beam quality degradation due to thermal lensing caused by lateral temperature gradients at high operating currents, which is exacerbated by the thermal barrier at the interface between the laser diode and metallization, making existing thermal path techniques less effective and costly.
Innovation Solution
A laser diode with a monolithically integrated thermal aperture formed in the semiconductor material, featuring a thermal conductivity coefficient lower than the surrounding material, to spatially selectively transport heat and reduce lateral temperature gradients, thereby flattening the thermal lens without requiring external heat sources or layer structure adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the resonator length is extended to improve heat transport, then heat dissipation is improved, but manufacturing cost increases
Solution Approach 1:
The patent divides the heat transport path into two segments: a first heat transport path through the first semiconductor substrate and a second heat transport path through the second semiconductor substrate. This segmentation allows heat to be dissipated through multiple parallel paths without extending the resonator length, thereby improving heat dissipation while avoiding increased manufacturing costs associated with longer resonators.
2Temperature
If external heat sources are added to reduce lateral temperature gradient, then thermal lens is flattened, but device complexity increases
Solution Approach 1:
The patent merges the heat transport function directly into the semiconductor substrates by forming heat transport paths within the substrate structure itself. The first and second semiconductor substrates are integrated with the active layer, and heat transport paths are formed by removing material or introducing low-thermal-conductivity regions within these substrates. This eliminates the need for separate external heat sources while achieving lateral temperature gradient reduction.
3Manufacturing precision
If layer structure is adjusted to improve beam quality, then lateral beam quality is marginally improved, but adaptability is reduced
Solution Approach 1:
The patent introduces heat transport paths with specific thermal conductivity properties at localized regions within the semiconductor substrates. These heat transport paths are formed by removing semiconductor material or introducing regions with lower thermal conductivity in specific locations beneath the active layer. This local modification of thermal properties enables effective control of lateral temperature gradients and beam quality without requiring comprehensive changes to the overall layer structure, thereby maintaining adaptability across different laser designs.
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 integrated thermal aperture effectively reduces lateral temperature gradients and thermal lensing, improving beam quality and reducing manufacturing costs by enhancing the thermal path technique's effectiveness within the laser diode.
Implementation Method 1
a thermal aperture formed in a layer shape with a thermal conductivity coefficient kblock smaller than a thermal conductivity coefficient kbulk of the p-doped semiconductor material is formed in the p-doped semiconductor material for spatially selective heat transport from the active zone
Data Source
AI summary
The present invention relates to a diode laser with an integrated thermal aperture. A laser diode (10) according to the invention comprises an active layer (14) formed between an n-doped semiconductor material (12) and a p-doped semiconductor material (16), wherein the active layer (14) forms an active zone (40) with a width w along a longitudinal axis for generating electromagnetic radiation; wherein in the p-doped semiconductor material (16) and/or in the n-doped semiconductor material (12) a thermal aperture (18) formed in a layer shape with a thermal conductivity coefficient kblock smaller than a thermal conductivity coefficient kbulk of the corresponding semiconductor material (16, 12) is formed for a spatially selective heat transport from the active zone (40) to a side of the corresponding semiconductor material (16, 12) opposite to the active layer (14).