Pulse compression and spectral broadening of stimulated Raman scattering in water via cascading amplification

Abstract

We used an energy-controllable two-cell setup to enhance stimulate Raman scattering (SRS) signal. The SRS enhancement method in this experiment was realized by combining SRS generation and amplification principles. The advantages it showed included the lower threshold of SRS and higher energy conversion efficiency, reaching up to 5.12%, approximately 2.21 times the energy conversion efficiency of 2.32% in a single sample cell. Therefore, the 2nd-order Stokes and 1st-order anti-Stokes SRS (Coherent anti-Stokes Raman spectroscopy—CARS) of water were obtained at lower pump energy in two sample cell condition than only one, and the energy transfer process of 2nd-order Stokes SRS was analyzed, the stimulated radiation wavelength covered from 450 to 832 nm. Furthermore, it showed a strong pulse width compression ability, the compression of pulse duration from 7 ns to 300 picoseconds (ps) was obtained. The amplified optical power of the leading edge of Stokes SRS was another aspect of reducing SRS threshold. Meanwhile, the observed maximum spectral broadening range was ≥460 cm −1 for the SRS output from cell2 (C2), while it was ≤100 cm−1 for cell1 (C1), which was attributed to the multiple cross-phase modulation (XPM) between the pump and Stokes lights sub-pulses.