Broadband multiplex coherent anti-Stokes Raman scattering microscopy employing photonic-crystal fibers

We demonstrate spectral multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy based on a single Ti:sapphire oscillator and a nonlinear photonic-crystal fiber (PCF). The Stokes pulse is generated by spectral conversion of the laser pulse in a PCF. The pump pulse is either a highly chirped pulse or a pulse spectrally compressed in a PCF. A region of the Raman spectrum from 800to4000 cm−1 is accessible with two different PCFs. Spectral resolution improvement by 1 order of magnitude over a transform-limited pump pulse utilizing a chirped or spectrally compressed pump pulse is demonstrated. The CARS spectrum is distorted for short, chirped pump pulses. We show that the quality of the spectrum is significantly improved when using a spectrally compressed pump pulse.