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.
we investigate experimentally the phenomenon of intra-envelope four-wave mixing in optical fibers. This phenomenon arises when two lasers, having nearly identical central frequencies, interact by four wave mixing process with each other. As a result, new spectral components are created within the existing spectra. We successfully isolate these components using a third laser through a multi-heterodyne detection process.
We experimentally demonstrate a novel approach to generate a multi-frequency comb light source with a high mutual coherence in an all-fiber system. Starting from EOM combs, we exploit spatial light multiplexing in a 3-core all-normal nonlinear silica fiber at 1550 nm. Each pulse propagates in its own core to experience a nonlinear broadening but within the same fiber. We obtained 3 almost similar output flat-top spectra spanning over 14 nm with 3 nJ per pulse at 250 MHz and a flat phase noise spectrum down to -125 dBc/Hz. The signal-to-noise ratio of interferograms is about 40 dB.
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