Coherent Raman spectroscopy with a fiber‐format femtosecond oscillator

Abstract

We report on the recent development of a new technological approach for coherent Raman spectroscopy/microscopy based on spectral compression of femtosecond pulses emitted by an amplified multiple‐branch Er:fiber oscillator. Spectral compression is achieved by group‐velocity mismatched second‐harmonic generation in periodically poled nonlinear crystals, and it allows efficient synthesis of multiple synchronized narrow‐bandwidth picosecond pulses with frequency difference continuously tunable from 1000 to 3500 cm −1 . The system offers performances close to the current state of the art both for coherent anti‐Stokes Raman scattering (CARS) and for stimulated Raman scattering (SRS), but with significant advantages in terms of compactness and versatility. In fact, several configurations can be easily implemented, including multiplex CARS, two‐color imaging and nonresonant background suppression in CARS. Copyright © 2012 John Wiley & Sons, Ltd.