Single pulse CARS noise: A comparison between single-mode and multimode pump lasers

An investigation of single pulse coherent anti-Stokes Raman spectroscopy, (CARS) noise, determined by the analysis of broadband nonresonant spectra, is described. It is shown that the use of a single-mode rather than a multimode pump laser leads to a significant reduction of CARS noise (40 percent), down to the level exhibited by the Stokes spectral profile itself. This reduction in noise is attributed to the minimization of the effects due to random variations in the laser temporal profiles by using temporally smooth single-mode laser pumps. A measurement of detector shot noise is presented and its effect on CARS noise is described. The advantages of using a single-mode pump laser in CARS spectroscopy are discussed.