Improvement of the signal-to-noise ratio in dual comb spectrometry through time multiplexing

We demonstrated a novel technique to improve the signal to noise ratio (SNR) of the frequency domain interferogram of a dual comb spectroscopy (DCS) setup, by about 5 dB, based on temporal shifting of the interfering pulse trains in the two channels. The experimental setup utilized a fiber based DCS architecture where electro-optic modulators (EOM) were used to generate two optical combs (or pulse trains). Due to this carefully adjusted periodic phase shifts, the interferogram now was time-multiplexed, or in other words included a larger number of peaks within a given time frame compared to when an unshifted case. There is nevertheless a tradeoff between the peak power and the bandwidth of the interferogram comb envelope in the spectral domain. The experimental results were also confirmed numerically and a relationship between the SNR improvement and the rate of phase shifting was established. These results open new possibilities in SNR improvement of EOM based multidimensional spectroscopic techniques and provide a powerful resource to execute sparse sampling and other complex techniques to maximize the amount of useful information in the interferogram data of a DCS setup.