New Technique Enhances Rapid High-Resolution Spectroscopy

A new technique in laser optical-feedback cavity-enhanced absorption spectroscopy has been introduced by researchers Christopher A. Curwen, Mathieu Fradet, and Ryan M. Briggs. The method, termed the scanning cavity OF-CEAS technique, allows for rapid collection of high-resolution spectra by continuously scanning the length of a high-finesse cavity. This process periodically locks a diode laser to the cavity resonance, resulting in a discrete set of transmission measurements that are evenly spaced in frequency.

The researchers demonstrated this technique using a fiber-coupled 1578-nm laser and a scanning Fabry-Perot cavity. They successfully measured a series of weak CO2 absorption lines with a frequency resolution of 15.6 MHz and a noise equivalent absorption coefficient of 10^-7 cm^-1. The measurements were limited by the moderate finesse of approximately 5000 and a short cavity length of about 5 cm. Notably, individual CO2 line shapes can be measured with high resolution in a single scan that takes only 67 milliseconds.

This advancement presents several advantages for in situ instruments, including small size, high spectral resolution, fast data collection, and minimal components. The implications of this technique could enhance various applications in environmental monitoring and atmospheric studies, where rapid and precise spectral data are essential. The findings are detailed in the paper titled "Scanning cavity OF-CEAS technique for rapid collection of high resolution spectra," available on arXiv with the identifier arXiv:2409.00309.