Detection of carbon monoxide using a polarization-multiplexed erbium dual-comb fiber laser

We present a compact, reliable, and robust free-running all-polarization-maintaining erbium (Er) single-cavity dual-comb laser generated via polarization multiplexing with gain sharing. Polarization multiplexing exploits the fast and slow axes of the fiber, while modelocking is achieved through a nonlinear amplifying loop mirror scheme using readily available components. The laser operates at a repetition rate of around 74.74 MHz with a tuning capability in the difference in repetition rates from 500 Hz to 200 kHz. This tunability makes the system more flexible for dual-comb spectroscopy experiments. Consequently, using this laser, we demonstrated a proof-of-principle dual-comb spectroscopy of carbon monoxide (CO), operating without any active stabilization.