Optical Kerr Gating as a Strategy for Noise Reduction in Femtosecond Stimulated Raman Spectroscopy

ABSTRACT We report a novel experimental approach, where an Optical Kerr gate is incorporated with femtosecond stimulated Raman spectrometry (FSRS) and functions as an efficient time domain filter that preferentially suppresses the inherent background associated with the FSRS technique. The latter typically requires the coaction of a narrow‐bandwidth Raman pulse ( R p ) of ps duration and an ultrashort White light probe ( WLp ) for broadband vibrational spectral coverage, while the vibrational signals are observed as gain features on top of the strong WLp background. Adding a high throughput optical filter of asymmetric temporal profile between the interaction region and the final spectral analysis step, a significant improvement of the FSRS signal‐to‐noise ratio was achieved. A suitable optical shutter is produced simply by using the golden standard CS 2 Kerr medium for Raman applications, providing a shutter opening shorter than a picosecond, due to the fast electronic response, followed by a strong nuclear response decaying in the ps timescale. The applicability of this approach is demonstrated by recording Raman spectra of common solvents with up to an order of magnitude improvement of the SNR ratio as compared with the normal (Kerr gate free) FSRS technique, along with a comparable spectral resolution. The experimental findings were complemented by simulations, sufficiently reproducing the main characteristics of the measurements.