Elliptical Absorption Cavity Waveguide Alignment for Gas Sensors
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Solution Overview
Problem
Current gas concentration sensors face limitations in sensitivity due to the constraints of integrating light sources and photo-detectors within the absorption cavity, which hampers the precision of gas concentration measurements.
Innovation Solution
The optical device positions the light source and photo-detector outside the absorption cavity, utilizing guided optics for beam processing, such as spectral filtering, to improve the signal-to-noise ratio and sensitivity, while maintaining compactness through the use of injection and extraction waveguides that adapt the mode size and orientation to optimize beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the light source and photo-detector are integrated inside the absorption cavity, then the device complexity is reduced, but the alignment precision and sensitivity deteriorate
Solution Approach 1:
The device is divided into separate functional modules: the absorption cavity for gas interaction, waveguides for light transmission, and external light source/photo-detector for precise alignment. This segmentation allows each component to be optimized independently while maintaining overall system functionality.
Solution Approach 2:
Waveguides are introduced as intermediary elements to couple the external light source and photo-detector with the absorption cavity. These waveguides enable precise alignment of optical components outside the cavity while maintaining efficient light coupling into the cavity mode.
2Measurement precision
If the light source and photo-detector are positioned outside the cavity using waveguides, then the alignment precision improves, but the device complexity increases
Solution Approach 1:
The waveguide structure is merged with the absorption cavity design, where the waveguide output is positioned at the cavity focus. This integration approach combines the benefits of external component placement with efficient optical coupling, reducing overall system complexity despite the added waveguide elements.
3Measurement precision
If the distance traveled by the analysis beam in the cavity is increased, then the sensitivity improves, but the cavity volume increases
Solution Approach 1:
The absorption cavity is designed with an elliptical cross-section, utilizing the optical properties of ellipses to guide the analysis beam along a longer path length within a compact volume. The elliptical geometry naturally focuses and redirects the beam to increase the effective optical path without proportionally increasing the cavity size.
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 enhances the sensitivity of gas concentration measurements by improving the precision of light source and photo-detector alignment and processing, leading to a better signal-to-noise ratio and increased sensitivity without altering the absorption cavity shape.
Implementation Method 1
The analysis beam emitted by the light source propagates in the cavity, is reflected on a reflecting wall of the latter, and returns to the photo-detector.
Implementation Method 2
an absorption cavity, the internal walls of which are provided with a reflective coating... a light source, for the emission of a so-called analysis light beam, and a photo-detector, for the detection of a measurement beam corresponding to the beam of analysis after partial absorption by the gas inside the cavity
Implementation Method 3
The invention also makes it possible to exploit the possibilities of guided optics to process the analysis beam before it enters the absorption cavity and/or the measurement beam leaving the absorption cavity
Data Source
Figure 1A~1B
Figure 2~4
Figure 5~6
AI summary
This optical device (100) for a biological or chemical sensor comprises an absorption cavity (110) intended to receive a biological or chemical medium; an injection waveguide (120) for injecting an analysis light beam (150) into the absorption cavity; and an extraction waveguide (130) for extracting a measurement light beam (160), corresponding to the analysis light beam after transit through the absorption cavity. The absorption cavity has a right-cylindrical shape with a base the shape of an elliptical segment. One end (121) of the injection waveguide is placed at a first focus (F1) of the ellipse and one and (131) of the extraction waveguide is placed at a second focus (F2) of the ellipse. The core of the injection waveguide (120) and the core of the extraction waveguide (130) each have a tip-shaped end, with a constant height in a plane parallel to the generatrix of the right cylinder and a tip-shaped cross section in planes parallel to the base of the right cylinder.