TUNABLE 50-FS PULSE GENERATION IN THE 250-310-NM ULTRAVIOLET RANGE

A newly designed high-repetition rate regenerative amplifier system pr oducing sub-50 fs, similar to 7 mu J pulses at 100 kHz (similar to 4 m u J at 250 kHz) is used to pump a fully tunable optical parametric amp lifier (OPA). The resulting transform Limited visible pulses in the 51 0-610-nm range have pulsewidths of similar to 40 fs and energies in th e range of 350-550 nJ, Doubling these pulses in thin (0.110-0.150 mm) BBO crystals results in near transform-limited ultraviolet (UV) pulses (255-305 mm) with high efficiency (20%-30%) across this tunable wavel ength range, The upconverted pulsewidths in the 0.110-mm crystal vary from 55 to 40 fs in the range from 255 to 305 mm correspondingly. Thes e pulsewidths are limited, particularly at the shortest wavelength, by group velocity mismatch of the fundamental and second harmonic pulses in the BBO, This system can be further optimized for the production o f even shorter pulses at these UV wavelengths.