Asymmetric spectral noise correlations in coherent Stokes and anti-Stokes Raman scatterings

Abstract

As a diagonal projection of the traditional generalized two-dimensional correlation function, a one-dimensional second-order correlation function in the frequency domain is introduced. This function was applied in coherent Stokes and anti-Stokes Raman scattering (CSRS/CARS) processes. The experiment was performed by a high-average-power fiber amplified femtosecond laser system with a 1 MHz repetition rate. To measure spectral noise fluctuations, sets of 30 sample spectra of pyridine solution were recorded in the fast sequence mode. Experimental design combined with the use of appropriate notch filters allowed for simultaneous recording of the CARS/CSRS spectra. Asymmetry in the noise fluctuations between CARS and CSRS processes is revealed by both one- and two-dimensional (synchronous as well as asynchronous) noise correlation calculations, demonstrating a potential for a high-resolution spectroscopic tool.