Dispersion‐compensated supercontinuum generation for ultrabroadband multiplex coherent anti‐Stokes Raman scattering spectroscopy

Abstract

AbstractWe have generated a dispersion‐compensated picosecond ultrabroadband supercontinuum light source at the sample position without using any additional compensator such as a prism pair or a grating pair. The dispersion‐compensated supercontinuum, which is obtained just by optimizing the length of a photonic crystal fiber, has been used as a Stokes laser source for ultrabroadband multiplex coherent anti‐Stokes Raman scattering (CARS) spectroscopy. Owing to an optimized temporal overlap between the narrowband pump and the Stokes supercontinuum pulses, a CARS signal has been obtained efficiently with a spectral coverage of more than 2800 cm−1. Furthermore, a vibrationally resonant CARS signal is observed not only when the pump pulse and the Stokes supercontinuum are temporally overlapped but also when the pump pulse follows the supercontinuum. It can be explained by an impulsive excitation of the vibrational coherence by the supercontinuum and a subsequent probe by a narrowband pump pulse. Using the dispersion‐compensated supercontinuum, we can perform not only the frequency‐domain multiplex CARS but also the time‐domain impulsive CARS measurement by controlling the delay time between the narrowband laser and the supercontinuum. Both these techniques can be applied to microspectroscopy in order to obtain the wide spectral range of vibrational resonances and the suppression of the nonresonant background. Copyright © 2006 John Wiley & Sons, Ltd.