Quantum Cascade Laser Array With Trench-Defined Non-Uniform Structure
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Solution Overview
Problem
Current compact laser sources in the mid- to long-wavelength infrared range lack sufficient power and compactness for applications such as missile-avoidance systems, laser photo-acoustic spectroscopy, and medical diagnostics, due to the absence of powerful and compact sources.
Innovation Solution
Semiconductor laser array devices with a quantum cascade laser structure, featuring a non-uniform lateral structure and trench regions with semi-insulating and high refractive index materials, which preferentially suppress unwanted array modes and enhance heat removal, allowing for high-power and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional laser structures are used, then device simplicity is maintained, but power output and efficiency are insufficient for mid- to long-wavelength infrared applications
Solution Approach 1:
The laser device is segmented into multiple element regions separated by interelement regions with trenches. This segmentation allows independent optimization of each element while collectively achieving high power output through array operation, resolving the contradiction between power output and structural simplicity.
Solution Approach 2:
Different regions of the laser structure are assigned different materials and properties: element regions contain active quantum cascade laser structures, while interelement regions contain trenches filled with semi-insulating and high refractive index materials. This local differentiation enables simultaneous achievement of high power output in element regions and thermal management in interelement regions.
2Reliability
If uniform lateral structure is used, then manufacturing is simplified, but unwanted array modes cannot be suppressed and single-mode operation is not achieved
Solution Approach 1:
The laser array employs asymmetric lateral structuring where interelement regions differ from element regions through the presence of trenches filled with specific materials. This asymmetry creates optical loss regions that suppress unwanted array modes while allowing the desired in-phase mode to operate, achieving reliable single-mode operation.
Solution Approach 2:
The trenches filled with semi-insulating and high refractive index materials create optical loss regions that would normally be considered harmful losses. However, these losses are strategically positioned to suppress unwanted array modes, converting what would be harmful losses into beneficial mode selection mechanisms that enable single-mode operation.
3Power
If standard heat removal structures are used, then device complexity is low, but heat dissipation is insufficient for high-power continuous wave operation
Solution Approach 1:
The interelement regions act as intermediary structures between element regions, containing trenches filled with materials that provide both optical loss for mode selection and thermal conduction pathways for heat removal. This intermediary structure enables simultaneous achievement of high continuous wave power and effective heat dissipation.
Solution Approach 2:
The interelement regions are designed to perform multiple functions simultaneously: providing optical loss for unwanted mode suppression, enabling thermal conduction for heat removal, and maintaining structural integrity. This multi-functionality allows high-power continuous wave operation without significantly increasing overall device complexity.
4Reliability
If high refractive index materials are not used in trenches, then manufacturing is simpler, but optical confinement and mode suppression are insufficient
Solution Approach 1:
The refractive index parameter of the trench filling material is specifically changed to high values to enhance optical confinement and mode suppression effects. This parameter change improves reliability of single-mode operation while the trench filling process remains compatible with standard semiconductor manufacturing techniques.
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 semiconductor laser array devices achieve high average output power and wallplug efficiency, enabling effective operation in various applications, including missile-avoidance systems and medical diagnostics, with a preferred in-phase array mode and reduced sensitivity to temperature variations.
Implementation Method 1
an upper trench layer comprising a material having a refractive index that is higher than that of the semi-insulating material
Implementation Method 2
a layer of thermally conducting material disposed above the upper trench layer
Implementation Method 3
quantum cascade laser structure
Data Source
AI summary
Semiconductor laser array devices capable of emitting mid- to long-wavelength infrared (i.e., 4-12 μm) radiation are provided. The devices include a quantum cascade laser (QCL) structure comprising one or more active cores; an optical confinement structure; a cladding structure, and a plurality of laterally-spaced trench regions extending transversely through the cladding and optical confinement structures, and partially into the QCL structure. The trench regions define a plurality of laterally-spaced interelement regions separated by element regions in the laser array device. The element regions are characterized by a non-uniform structure across their widths. As a result of this structural non-uniformity, array modes composed of coupled first-order lateral modes of the element regions are preferentially suppressed relative to array modes composed of coupled fundamental lateral modes of the element regions.