Bidirectional QCL Gain Structure for Wider Wavelength Sweeps
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Solution Overview
Problem
The wavelength band that can be swept by existing external resonance-type laser module devices using a QCL device is limited by the wavelength band of the gain generated by current injection, as the MEMS diffraction grating returns a wider wavelength band than the QCL device's gain.
Innovation Solution
A QCL device with a core region comprising alternating barrier and well layers, allowing current injection in two directions to create two different gain bands, and a MEMS diffraction grating for reflecting and returning light, enabling a wider wavelength sweep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current injection is used to generate gain in the QCL device, then laser emission is achieved, but the wavelength band is limited to the gain band of the QCL device
Solution Approach 1:
The core region is divided into multiple stages, each stage containing an active region and an injector region with specific quantum well structures. This segmentation allows different stages to contribute to different wavelength bands, enabling the QCL device to cover a broader wavelength range by combining the gain bands of multiple stages.
Solution Approach 2:
The patent introduces a new dimension of operation by enabling current injection in both forward and reverse directions through the core region. This bidirectional current injection capability creates two distinct gain bands, effectively doubling the wavelength sweep range beyond what single-direction injection can achieve.
2Adaptability or versatility
If a single gain band is provided in the QCL device, then the device structure is simple, but the wavelength sweep range is limited
Solution Approach 1:
The core region is segmented into multiple identical or similar stages, each with an active region and injector region. This modular segmentation allows the device to achieve extended wavelength coverage while maintaining a relatively simple repeating structure, reducing the complexity compared to designing entirely different structures for each wavelength band.
Solution Approach 2:
Each stage in the core region is designed to be multi-functional, capable of contributing to both forward and reverse current injection gain bands. This universality allows the same structural unit to serve multiple wavelength ranges, reducing the need for additional specialized components and thereby limiting the increase in overall device complexity.
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
Enables a wavelength sweep over a wider wavelength band by providing two different gain bands, enhancing the capabilities of the QCL device and module device.
Implementation Method 1
an active region in which a plurality of alternating barrier layers and well layers are formed and which emits light
Implementation Method 2
an injector region in which a plurality of alternating barrier layers and well layers are formed and which injects electrons into the active region
Implementation Method 3
a MEMS diffraction grating, wherein the MEMS diffraction grating includes a diffraction reflecting section which diffracts and reflects light emitted from the QCL device
Data Source
AI summary
A QCL device includes first and second electrodes. When an electric field is applied from the second electrode to the first electrode, first to fourth subbands are formed. The second subband has a higher energy level and a higher electron density than the first subband. Light emits when electrons transition from the second subband to the first subband. The third subband has a lower energy level and the fourth subband has a higher energy level than the second subband. When an electric field is applied from the first electrode to the second electrode, fifth to eighth subbands are formed. The sixth subband has a higher energy level and a higher electron density than the fifth subband. Light emits when electrons transition from the sixth subband to the fifth subband. The seventh subband has a lower energy level and the eighth subband has a higher energy level than the sixth subband.