Optical Cavity Mirror Fabrication Using Multi-Shot Quantum Cascade Lasers
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Solution Overview
Problem
The fabrication of mirrors for microscopic optical cavities requires high accuracy in material removal, with demands for stability and reproducibility that are challenging to meet with existing technologies.
Innovation Solution
A method combining the use of a quantum cascade laser (QCL) with a multi-shot sequence for material removal from an optical substrate, such as an optical fiber, to generate a concave surface profile with high precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single CO2 laser pulse train is used for material removal, then the fabrication process is simple, but the surface accuracy and roughness control are insufficient
Solution Approach 1:
The fabrication process is divided into multiple sequential laser shots instead of using a single pulse train. Each shot removes material layer by layer with controlled depth, allowing progressive refinement of the surface profile. This segmentation enables achieving nanometer-level accuracy (surface roughness < 0.1 nm) by cumulative precision control across multiple shots.
Solution Approach 2:
The method employs periodic laser shots with controlled intervals between pulses. The periodic application of laser energy allows the material to be removed in controlled cycles, with each cycle contributing to the final surface precision. This periodic action enables thermal management and precise control over material removal rate and surface quality.
2Manufacturing precision
If multiple laser shots are applied sequentially, then the material removal accuracy improves, but the fabrication time increases
Solution Approach 1:
The multiple laser shots are applied in a continuous sequential manner without interrupting the fabrication process. Each shot immediately follows the previous one, maintaining continuous material removal action. This continuity ensures that the accumulated precision from multiple shots is achieved without idle time, balancing accuracy improvement with reasonable fabrication speed.
3Productivity
If high laser power is used for rapid material removal, then the productivity increases, but the surface roughness deteriorates
Solution Approach 1:
Instead of using excessive high power that would damage the surface, the method applies partial action with multiple lower-power shots. Each shot removes a portion of the required material depth, and the cumulative effect of multiple partial removals achieves the total material removal goal while maintaining surface integrity. This partial action approach prevents surface roughness deterioration that would occur with single high-power shots.
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 achieves a surface roughness of 0.1 nm and overall accuracy in the order of nanometers, enabling the creation of complex and precise mirror geometries for microscopic optical cavities.
Implementation Method 1
a first material portion of the optical substrate, in particular of the fiber core, is removed due to laser ablation by applying the sequence of multiple laser shots
Implementation Method 2
a second material portion of the optical substrate, in particular of the fiber core, is melted, in particular melted and not removed, by applying the sequence of multiple laser shots
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
For at least partial fabrication of a mirror for an optical cavity (16), a surface (13) to be processed of an optical substrate (1) is positioned in an operating plane (35), which is equal to or parallel to a focal plane of a laser arrangement (2), and a concave surface profile (14, 33) of the surface (13) is generated by applying a sequence of multiple laser shots to the surface (13) by using a quantum cascade laser (6) of the laser arrangement (2).