Bioinspired Mode-Noise Suppressed Off-Axis Integrated Cavity for Rapid Dynamic Gas Detection

Area of Science:

• Spectroscopy
• Fluid Dynamics
• Bioinspired Engineering

Background:

• Traditional off-axis integrated cavities (OAICs) suffer from mode interference noise and slow gas exchange due to nonuniform airflow.
• Large inside airflow fluctuations in conventional OAICs hinder precise gas detection.

Purpose of the Study:

• To introduce a bioinspired mode-noise suppressed OAIC that mimics bacterial flagella to overcome limitations of traditional OAICs.
• To enhance cavity-enhanced spectroscopy by integrating bioinspired design principles for improved performance.

Main Methods:

• Redesigned gas inlets into bioinspired tangential inlets to create a rotating flow, similar to bacterial flagella.
• Employed multiobjective optimization using a genetic algorithm to fine-tune OAIC parameters for uniform fluid dynamics.
• Utilized cavity-enhanced spectroscopy for gas detection and Allan deviation analysis for performance evaluation.

Main Results:

• The bioinspired OAIC maintained stable performance across a 200-1500 sccm flow range without significant concentration fluctuations.
• Achieved a 2.54-fold reduction in optical mode-noise level at 800 sccm and shortened complete gas exchange time to 12 seconds.
• Demonstrated a detection limit of 34.4 parts-per-trillion (ppt) with an average time of 13.5 seconds, indicating high sensitivity and stability.

Conclusions:

• The bioinspired OAIC design effectively suppresses airflow fluctuations and minimizes mode noise, enabling long-term stability in high-airflow gas detection.
• This bioinspired approach offers a promising strategy for improving resonant cavity performance in fluid measurements.
• The design concept is adaptable for fabricating other resonant cavities used in various fluid measurement applications.