Abstract

We demonstrate an alternative light source for CARS microspectroscopy based on a fiber laser and a photonic-crystal fiber. The light source simultaneously delivers a picosecond pump pulse at 1033.5 nm and a frequency-shifted femtosecond Stokes pulse, tunable from 1033.5 nm to 1400 nm. This corresponds to a range 0 – 2500 cm⁻¹, so that Raman-active vibrations in this frequency range can be probed. The spectral resolution is 5 cm⁻¹, given by the spectral width of the pump pulse. The frequency range that can be probed simultaneously is 200 cm⁻¹-wide, given by the spectral width of the Stokes pulse. The achievable average powers are 50 mW for the pump and 2 mW for the Stokes pulse. The repetition rate is 35 MHz. We demonstrate the capability of this light source by performing CARS microspectroscopy and comparing CARS spectra with Raman spectra.

© 2007 SPIE