Real-time dual frequency comb spectroscopy in the near infrared

We use two femtosecond lasers with slightly different repetition rates to perform real-time dual frequency comb spectroscopy in the near infrared. The difference between the repetition rates is δ = 4403 Hz, yielding a minimal time interval between subsequently measured interferograms and spectra of 0.227 ms. It takes as short as 4 μs to record a single interferogram, opening the possibility of studying dynamical processes. We work with different spectral outputs from two Erbium-doped fiber lasers and employ a grating based spectral filter in a 2f-2f setup to select the common spectral region of interest, thereby increasing the signal-to-noise ratio.