Multiwavelength Quantum Cascade Laser via Lateral Core Segmentation
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Solution Overview
Problem
Current semiconductor-based lasers for mid-IR applications have limited optical gain bandwidth, resulting in low lasing efficiency due to the contribution of only a part of the total stack to lasing, especially when multiple differing stages are stacked in the growth direction.
Innovation Solution
The method involves forming multiple differing cores in the lateral direction, positioned in-plane relative to each other within a single wafer, allowing each core to be optimized for high lasing efficiency and power at specific wavelengths, with each core structured as a quantum cascade gain medium emitting within the mid-IR range, and optionally including passive or active core regions for enhanced wavelength coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple differing stages are stacked in the growth direction to increase wavelength coverage, then the optical gain bandwidth increases, but the lasing efficiency decreases because only a part of the total stack contributes to lasing
Solution Approach 1:
The patent segments the laser structure into multiple lateral cores instead of stacking stages vertically. Each core is etched and grown separately on the substrate, allowing independent optimization of each core's active region for specific wavelengths. This segmentation enables all cores to contribute efficiently to lasing simultaneously, resolving the efficiency loss problem while achieving broad optical gain bandwidth through the combined output of multiple specialized cores.
Solution Approach 2:
The patent transitions from vertical stacking of stages (growth direction) to lateral arrangement of cores (in-plane direction). This dimensional change allows each core to be optimized independently for high efficiency at its specific wavelength while all cores operate simultaneously in the lateral plane, achieving both broad bandwidth and high lasing efficiency that cannot be achieved through vertical stacking alone.
2Device complexity
If a single core is designed to emit multiple wavelengths, then the device complexity is reduced, but the wavelength coverage is limited to about 15-20% of the center wavelength
Solution Approach 1:
The patent merges multiple individual cores into a single integrated device structure on one substrate. Each core maintains its own optimized active region for specific wavelengths, but they are combined in the lateral direction to function as a unified multi-wavelength laser source. This merging achieves broad wavelength coverage (3-14 μm) while keeping the overall device structure relatively simple and manufacturable.
3Measurement precision
If gratings with different periods are added to a single core to achieve multiple wavelengths, then the wavelength selection precision improves, but the overall efficiency remains limited by the single core's gain bandwidth
Solution Approach 1:
The patent applies local quality by designing each lateral core with a specific active region structure optimized for particular wavelengths. Instead of using a single core with broad gain bandwidth and adding gratings for wavelength selection, each core is locally optimized to contribute efficiently at its designated wavelengths, with grating structures added to each core for precise wavelength selection. This ensures both high efficiency and precise wavelength control.
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 significantly increases the mid-IR optical gain bandwidth and improves lasing efficiency by allowing each core to contribute optimally to the lasing process, enabling wider wavelength coverage and higher power output.
Implementation Method 1
At least one of the core structures comprises a quantum cascade gain medium emitting at a frequency within the range from 3-14 μm
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
Disclosed is a method of forming a laser source capable of producing mid-IR laser radiation comprises growing a first core structure on a substrate, etching away the first core structure in one or more locations, and growing a second core structure on the substrate. At least one of the core structures comprises a quantum cascade gain medium emitting at a frequency within the range from 3-14 μm. Also disclosed is a laser source capable of producing mid-IR laser radiation comprising a quantum- cascade core positioned on a substrate for emitting within the range from 3-14 μm and a second core on the substrate positioned in-plane relative to the first core. The second core is one of a) a passive waveguide core b) a second quantum-cascade core and c) a semiconductor active core region.