Orthogonal Grating Photonic Crystal for Dual-Wavelength Quantum Cascade Laser
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Solution Overview
Problem
Conventional surface-emitting quantum cascade lasers emit infrared laser light with a single wavelength, which limits their ability to generate terahertz waves with different frequencies, as terahertz wave generation requires infrared laser light with multiple wavelengths.
Innovation Solution
A surface-emitting quantum cascade laser design featuring a photonic crystal layer with orthogonal rectangular gratings in different regions, allowing for the emission of two infrared laser lights with distinct wavelengths, which are then used to generate terahertz waves through Cherenkov phase matching, enabling efficient terahertz wave emission perpendicular to the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the two-dimensional grating has the same pattern over the entire surface of the light outgoing surface, then the structure is simple and easy to manufacture, but the infrared laser light is emitted with a single wavelength which limits terahertz wave generation capability
Solution Approach 1:
The light outgoing surface is divided into multiple regions, each region having a two-dimensional grating with a different pattern. This segmentation allows different regions to emit infrared laser light at different wavelengths, enabling terahertz wave generation while maintaining manufacturing simplicity through modular design
Solution Approach 2:
Different regions of the light outgoing surface are assigned different grating patterns optimized for specific wavelength emissions. This local differentiation enables each region to contribute to a specific wavelength channel, achieving multi-wavelength capability without complicating the overall manufacturing process
2Adaptability or versatility
If the photonic crystal layer includes multiple regions with different grating patterns, then multiple wavelengths can be emitted for terahertz wave generation, but the device structure becomes more complex
Solution Approach 1:
Multiple functional regions with different grating patterns are merged into a single integrated photonic crystal layer. This combining approach achieves multi-wavelength emission capability while avoiding the complexity of separate devices, as all regions are fabricated together in one layer structure
Solution Approach 2:
The photonic crystal layer is designed to perform multiple functions simultaneously - each region emits at a different wavelength, and the layer as a whole enables terahertz wave generation. This multi-functionality reduces the need for separate components, thereby managing 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
This design enables the simultaneous emission of two infrared laser lights with different wavelengths, facilitating the generation of terahertz waves with a wide frequency range, enhancing the capability for detecting specific substances by terahertz wave irradiation and reflection analysis.
Implementation Method 1
The active layer is capable of emitting a first and a second infrared laser light by intersubband transition
Implementation Method 2
When a photonic crystal layer including a two-dimensional grating has anisotropy, it provides a surface-emitting quantum cascade laser capable of emitting infrared laser light in a direction generally perpendicular to the active layer
Implementation Method 3
a nonlinear optical layer having optical nonlinearity, placed on the active layer, and capable of generating a terahertz wave by Cherenkov phase matching
Data Source
AI summary
A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.