Cavity-enhanced dual-comb spectroscopy with wide spectral band tuning

Abstract

Cavity-enhanced dual-comb spectroscopy holds significant research value by combining the high sensitivity of cavity enhancement and dual-comb high resolution and rapid measurement. However, due to the presence of intracavity dispersion, the insufficient coupling between the enhancement cavity and the optical frequency comb restricts the measurement bandwidth of the system, making it unable to provide abundant spectral information of the sample. To overcome this limitation, we propose a cavity-enhanced dual-comb spectroscopy with wide spectral band tuning by a single-point locking tuning scheme, which achieves a tuning capability of over 9 THz at the central wave number of 6400 cm−1. This represents a significant improvement compared to the untuned cavity-enhanced spectrum, increasing the measurable bandwidth by 2.5 times. We verified the capability of the scheme by measuring the rovibrational spectrum of CO2 in various frequency bands within the 6250–6550 cm−1 range. In each tuned frequency band, we achieved an enhancement factor of ∼950, signal-to-noise ratio (SNR > 600) in 30 s, and resolution of 250 MHz. The cavity-enhanced dual-comb spectroscopy with wide spectral band tuning holds promise for potential applications in fields such as trace gas analysis and respiratory diagnostics.