High spectral resolution multiplex CARS spectroscopy using chirped pulses

A simple technique for achieving high spectral resolution coherent anti-Stokes Raman scattering (CARS) spectra with a femtosecond laser system is presented. A linearly chirped and stretched (similar to10 ps) pump pulse generates CARS signal only when overlapped in time with the Stokes pulse (90 fs), creating a 'temporal slit' that defines the spectral resolution of the technique. Multiplex CARS spectra for liquid methanol and liquid isooctane are presented, demonstrating a spectral resolution of better than 5 cm(-1). This new chirped (c-CARS) technique should prove useful for chemically-selective imaging applications, as it significantly reduces the non-resonant background contribution. (C) 2004 Elsevier B.V. All rights reserved.