Frequency comb interference spectroscopy using a fiber laser comb and a multi-colour laser

In this paper, we demonstrate a rapid high-resolution frequency comb spectrometer involving a mode-locked laser comb and a multi-colour laser. The heterodyne detection of the two lasers enables hundreds of thousands of Doppler-limited molecular spectra to be recorded in a second. With this device, several P-branch transitions of the H¹³CN (gas) 2ν₃-band are simultaneously interrogated at comb-line-defined resolution (54.5 MHz or 0.5 pm) within 3 μs. The single-measurement spectrum spans >200 GHz (∼1.6 nm) far beyond the electronic bandwidth (33 GHz) of our acquisition system. Without using asynchronous combs or dispersers and detection arrays, the spectrometer may benefit many gas sensing applications, such as environmental monitoring.