Terahertz QCL Laser Module With Support-Mediated Wave Extraction
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Solution Overview
Problem
The process of polishing the end surface of a substrate in terahertz quantum cascade lasers is difficult, leading to reduced productivity and potential damage to the substrate during alignment with a lens for terahertz wave output.
Innovation Solution
A laser module design that includes a support member to output terahertz waves through its internal structure, eliminating the need for a polished substrate surface and stabilizing the substrate's fixation, while incorporating a reflection film to enhance light oscillation efficiency and using separate members for the support member to facilitate manufacturing and improve heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the end surface of the substrate is polished to be inclined to avoid total reflection of terahertz wave, then the terahertz wave extraction efficiency is improved, but the manufacturing complexity and difficulty increase
Solution Approach 1:
A support member is introduced as an intermediary component between the substrate and the external environment. The support member includes a holding portion that contacts the back surface of the substrate and a protruding portion that provides the inclined surface for terahertz wave extraction. This transfers the polishing requirement from the fragile substrate to the more robust support member, improving manufacturability while maintaining extraction efficiency.
Solution Approach 2:
The device is divided into separate functional components: the substrate (for generating terahertz waves), the active layer, and the support member (for extraction and structural support). This segmentation allows the support member to bear the mechanical stress of polishing and handling, while the substrate remains intact and undamaged.
2Reliability
If the end surface of the substrate is pressed against the lens surface for positioning to increase extraction efficiency, then the terahertz wave output is improved, but the substrate may be damaged
Solution Approach 1:
The support member acts as a mediator that absorbs mechanical stress during positioning and handling. The lens is positioned against the protruding portion of the support member rather than directly against the substrate, preventing substrate damage while maintaining proper alignment for efficient terahertz wave extraction.
Solution Approach 2:
The support member provides structural cushioning and protection to the substrate before any damaging forces are applied. By designing the support member with appropriate mechanical properties and geometry, it preemptively protects the substrate from damage during assembly, positioning, and operation.
3Reliability
If a polished inclined surface is formed on the substrate to output terahertz waves, then the extraction efficiency is improved, but the productivity decreases due to difficult processing
Solution Approach 1:
The support member serves as a mediator that takes on the complex polishing requirement. Since the support member can be manufactured more easily and withstands the polishing process better than the substrate, this approach maintains high extraction efficiency while significantly improving manufacturing productivity.
Solution Approach 2:
Instead of polishing the substrate to achieve the inclined surface, the invention inverts the approach by providing the inclined surface through the support member's protruding portion. This reversal of roles between substrate and support structure solves the productivity problem while maintaining the required optical functionality.
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 enhances productivity by avoiding substrate damage and polishing difficulties, increases terahertz wave extraction efficiency, and improves light oscillation and heat dissipation, resulting in a more reliable laser module.
Implementation Method 1
an active layer provided on an opposite side of the first clad layer from the substrate and configured to generate a terahertz wave having a difference frequency between a first frequency and a second frequency
Implementation Method 2
a first active-layer-surface that constitutes a part of the first end surface and constitutes a resonator for oscillating light of the first frequency and light of the second frequency
Data Source
AI summary
The laser module includes a QCL element and a support member. The QCL element has a first end surface located on a first side in a second direction orthogonal to a stacking direction and a second end surface located on a second side opposite to the first side in the second direction. The substrate has first to fourth substrate-surfaces. The support member has a first portion having a first surface facing at least a portion of the fourth substrate-surface, and a second portion having a second surface facing at least a portion of the first substrate-surface and a third surface located opposite to the second surface in the second direction. At least a part of the terahertz wave generated in the active layer is incident on the second surface of the support member through the substrate and is emitted from the third surface through the inside of the second portion.