Efficient generation of picosecond pulses at 243 nm

A new method is reported for generating tunable picosecond light pulses in the ultraviolet region of the spectrum. The system consists of a synchronously pumped mode-locked coumarin 102 dye laser which is mode-matched into an enhancement ring cavity with a mode spacing tuned to the repetition rate of the dye laser. A frequency modulation locking technique locks the carrier frequency of the mode-locked dye laser pulse train to the enhancement cavity. A beta-barium borate crystal was used to produce an average power of greater than 70 mW at 243 nm. There are many potential applications for this source, including the investigation of the 1S to 2S transition in atomic hydrogen using Doppler-free two-photon coherent multiple pulse spectroscopy