Femtosecond traveling-wave parametric generation with lithium triborate

Ultrashort pulses, of the same time duration as the pump pulse, have been obtained with a traveling-wave parametric generator employing a temperature-tuned lithium triborate crystal in noncritical phase matching. Starting from a 190-fs pulse at 0.6 um generated by a dye laser, we achieved an overall conversion efficiency of 10-15% in the tuning range 0.85-0.97 Am (and the corresponding range of 1.6-2.1 um) with a pump energy of only 30 uJ. The easy operation in the femtosecond regime and the minimal energy requirements that we found are due to the small group-velocity mismatch of lithium triborate at this pump wavelength and to the absence of walk-off.