Optical Cavity Mirror Shaping With Multi-Shot Quantum Cascade Laser
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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 and fabrication arrangement that utilize a quantum cascade laser (QCL) with a multi-shot sequence to remove material 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
1Productivity
If a single CO2 laser pulse train is used to remove material, then material removal efficiency is improved, but manufacturing precision deteriorates due to inability to achieve high accuracy of a few nanometers
Solution Approach 1:
The fabrication process is divided into multiple sequential laser shots instead of using a single pulse train. Each shot removes a portion of material, and the cumulative effect of multiple shots achieves the desired precision of a few nanometers while maintaining efficient material removal.
Solution Approach 2:
The laser is applied in periodic pulses with controlled intervals, allowing the material to respond to each pulse in a predictable manner. This periodic application enables precise control over the material removal process, achieving both efficiency and high manufacturing precision.
2Productivity
If high power laser is used to remove material quickly, then productivity is improved, but manufacturing precision deteriorates due to thermal effects and material damage
Solution Approach 1:
The laser power is applied in periodic pulses rather than continuous high power, allowing thermal diffusion to occur between pulses. This prevents excessive heat accumulation and thermal damage to the material, maintaining surface quality while still achieving efficient material removal through cumulative effect.
Solution Approach 2:
Multiple preliminary laser shots are applied before the final shaping shots. These preliminary shots remove the bulk material efficiently, while the final shots with lower power or different parameters refine the surface to achieve the required precision and quality.
3Manufacturing precision
If the laser beam is focused to a small spot for precision, then manufacturing precision is improved, but the area of material removal is limited, reducing productivity
Solution Approach 1:
The material removal process is segmented into multiple passes with the focused laser beam. Different regions of the surface are treated in sequence, with the beam positioned at different locations for each shot. This allows the use of a small focused spot for precision while still processing larger areas through multiple sequential operations.
Solution Approach 2:
The fabrication process extends into the temporal dimension by using multiple shots over time, rather than attempting to remove all material in a single pass. This multi-temporal approach allows a small focused beam to achieve both precision and productivity by accumulating material removal across many sequential operations.
4Manufacturing precision
If multiple laser shots are applied to achieve high precision, then manufacturing precision is improved, but the time required increases, reducing productivity
Solution Approach 1:
The laser shots are applied periodically with optimized intervals that allow efficient material removal while achieving the desired precision. The periodic timing is tuned so that each shot contributes maximally to the final surface quality without unnecessary delays, balancing precision requirements with fabrication time.
Solution Approach 2:
The number of laser shots is optimized to provide just enough material removal to achieve the desired precision, avoiding excessive shots that would waste time. The process uses the minimum necessary number of shots to reach the target surface roughness of 0.1 nm, eliminating redundant operations.
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
Achieves a surface roughness of 0.1 nm and overall accuracy of nanometer dimensions, allowing for complex and flexible mirror geometries, including freeform surfaces, while improving stability and reproducibility.
Implementation Method 1
A first material portion of the optical substrate, for example of the optical fiber, 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, for example of the optical fiber, in particular of the fiber core, is melted, in particular melted and not removed, by applying the sequence of multiple laser shots
Data Source
AI summary
For at least partial fabrication of a mirror for an optical cavity, a surface to be processed of an optical substrate is positioned in an operating plane, which is equal to or parallel to a focal plane of a laser arrangement, and a concave surface profile of the surface is generated by applying a sequence of multiple laser shots to the surface by using a quantum cascade laser of the laser arrangement.