Multi-pass Cavity for CRDS with Turning Mirrors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cavity ring-down spectroscopy systems face challenges in increasing optical path length without significantly increasing device footprint, while maintaining sensitivity, as longer optical paths often result in absorption and reflectivity losses that degrade light intensity.
Innovation Solution
The implementation of multi-pass cavities with a pair of flat mirrors and turning mirrors within a gas channel, allowing for multiple bounces of light to increase optical path length without substantial absorption and reflectivity losses, thereby enhancing sensitivity with a smaller footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between the two reflective mirrors is increased to increase optical path length, then sensitivity is improved, but the overall footprint of the device increases
Solution Approach 1:
The patent introduces a multi-pass cavity configuration where light travels through the gas sample multiple times by reflecting between mirrors at different angles and positions. This transforms a single-pass linear path into a multi-dimensional optical path that folds back on itself, achieving extended optical path length within a compact three-dimensional space rather than requiring a simple linear extension.
2Measurement precision
If the number of bounces of light between two physical positions is increased to increase optical path length, then sensitivity is improved, but light intensity is reduced due to absorption and reflectivity losses
Solution Approach 1:
The patent employs super-polished mirrors with enhanced reflectivity coatings specifically designed for the operating wavelength, changing the optical parameters of the reflecting surfaces to minimize absorption and scattering losses. This allows for multiple bounces while maintaining adequate light intensity for detection.
3Measurement precision
If the number of bounces of light is increased to increase optical path length, then sensitivity is improved, but the device complexity increases
Solution Approach 1:
The patent integrates the multi-pass optical cavity directly into the device housing, merging the optical path folding function with the structural support function. The mirrors are mounted on the housing itself, and the gas flow channels are incorporated into the same structure, reducing the number of separate components and simplifying alignment while achieving multiple bounces.
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 configuration achieves a longer effective optical path length with reduced footprint, maintaining high light intensity and sensitivity for gas analysis, such as detecting SARS-CoV-2, by using super-polished mirrors and wavelength-dependent coatings to minimize losses, allowing for precise detection of gas compositions down to parts per trillion levels.
Implementation Method 1
a pair of flat mirrors positioned parallel to each other within the gas channel to form a resonance cavity
Implementation Method 2
The first turning mirror is configured to reflect the light beam from the first light transmission axis toward the resonance cavity
Implementation Method 3
each additional bounce may lower the light intensity (and thus lower the sensitivity) due to, e.g., absorption and reflectivity losses
Data Source
AI summary
Multi-pass cavities for cavity ring-down spectroscopy. The multi-pass cavity includes, in one example, a body, a pair of flat mirrors, a light input coupler, a first turning mirror, a second turning mirror, and a light output coupler. The pair of flat mirrors are positioned parallel to each other within a gas channel of the body. The light input coupler is configured to direct a light beam into the gas channel along a first transmission axis. The first turning mirror is configured to reflect the light beam from the first transmission axis toward the resonance cavity. The light output coupler is configured to direct a first portion of the light beam out of the gas channel and reflect a second portion of the light beam along a second transmission axis. The second turning mirror is configured to reflect the light beam from the second transmission axis to the resonance cavity.