Angled-Active-Region QCL With α-DFB Grating for High-Power Beam Quality
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Solution Overview
Problem
Quantum cascade lasers (QCLs) face challenges in scaling average optical power while maintaining beam quality due to self-heating issues, which limits the active region width and prevents the application of α-DFB configurations for high power QCLs.
Innovation Solution
Employing ultra-thin active regions with low thermal resistance and shallow ridge or simple contact-stripe configurations, combined with α-DFB gratings for spatial mode selection, to suppress mode reflection and achieve high average power operation without sacrificing beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the active region width is increased to scale average optical power, then the optical power output is improved, but self-heating issues worsen and beam quality deteriorates
Solution Approach 1:
The active region is divided into multiple quantum wells separated by barriers, creating a segmented structure that allows heat to be managed more effectively while maintaining high optical power output through multiple emission pathways
Solution Approach 2:
The patent transitions from traditional planar active regions to vertically-canted active regions that extend in three dimensions, allowing heat dissipation in additional spatial directions while maintaining high power density and beam quality
2Power
If the active region width is increased to scale average optical power, then the optical power output is improved, but beam quality worsens
Solution Approach 1:
The patent implements localized optical gratings and distributed feedback structures that maintain high beam quality in specific regions while allowing the overall active region to be scaled for high power output, creating different functional zones within the laser structure
3Ease of manufacture
If traditional edge-emitting QCL configurations are used, then manufacturing is simplified, but high power operation with maintained beam quality cannot be achieved
Solution Approach 1:
The patent employs asymmetric quantum well and barrier thicknesses within the active region, as well as asymmetric grating structures, that are optimized for high power operation while remaining compatible with standard semiconductor fabrication processes
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 approach enables QCLs to operate efficiently at high power levels, reducing the price per watt and allowing for high brightness infrared laser sources, with potential applications exceeding 100 W of optical power in a high brightness beam.
Implementation Method 1
quantum cascade lasers (QCLs)... each injected electron can emit multiple photons and therefore enhance laser gain
Implementation Method 2
α-DFB gratings for spatial mode selection
Implementation Method 3
Multiple active regions are 'cascaded' so that each injected electron can emit multiple photons
Implementation Method 4
each injected electron can emit multiple photons and therefore enhance laser gain
Implementation Method 5
Employing ultra-thin active regions with low thermal resistance
Implementation Method 6
α-DFB gratings for spatial mode selection... suppress mode reflection
Implementation Method 7
optical grating being adjacent the active region and configured to emit one of a continuous wave (CW) laser output or a pulsed laser output
Data Source
AI summary
A QCL may include a substrate, an emitting facet, and semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the emitting facet of the substrate. The QCL may include an optical grating being adjacent the active region and configured to emit one of a CW laser output or a pulsed laser output through the emitting facet of substrate.