Femtosecond OPO based on LBO pumped by a frequency-doubled Yb-fiber laser-amplifier system for CARS spectroscopy

Femtosecond OPO based on LBO pumped by a frequency-doubled Yb-fiber laser-amplifier system for CARS spectroscopy –Feb 2011

C Cleff, J Epping, P Gross and C. Fallnich – Applied Physics B: Lasers and Optics
We present detailed investigations of a femtosecond green-pumped optical parametric oscillator (OPO) based on lithium triborate. As pump source, a frequency-doubled Yb-fiber laser-amplifier system is used. The OPO generates signal pulses tunable over a spectral range from 780 to 940 nm and idler pulses tunable from 1630 to 1190 nm. More than 250 mW are generated in the signal beam and more than 300 mW in the idler beam. Without dispersion compensation chirped signal pulses with a pulse duration between 100 and 250 fs are measured. Using this system for coherent anti-Stokes Raman scattering spectroscopy, vibrational resonances between 1110 and 6760 cm−1 can be excited. Due to the chirped pulses, a spectral resolution of 100 cm−1 is achieved, which is 2.5 times higher compared to an excitation with time-bandwidth limited pulses. … The emission wavelengths were measured with a grating-based spectrometer (Stellarnet BLUE-Wave,0.5-nm resolution), and for each data point of the temperature tuning curve, the signal output power was optimized over the res- onator length for each crystal temperature.