Polarization-Multiplexed Erbium Single-Cavity Dual Comb and Detection of Carbon Monoxide

Dual-comb spectroscopy (DCS) has become a ubiquitous tool for field-deployable spectroscopy [1]. Due to its advantages, DCS has applications in various fields, such as absorption spectroscopy and ranging [2]. A dual-comb (DC) laser consists of two optical pulse trains with slightly different repetition rates scanning over each other. The optical beating between the two combs generates an interferogram, recorded using a fast photodiode. The resulting down-converted spectrum contains information from the optical domain. However, to utilize the full potential of this laser, the two combs must be mutually coherent. With two independent free-running lasers, achieving mutual coherence can become cumbersome. One technique to improve mutual coherence is using a single-cavity (SC) DC laser. Having the two combs generated from a single cavity will enhance the mutual coherence due to common-mode noise cancellation. A DC system is, therefore, a light source and a high-resolution spectrometer with a faster acquisition rate (typically on the order of a few kHz).