Generation of tunable radiation between 250 nm and MW power levels

It is proposed that tunable coherent radiation below 250 nm may be generated by sum frequency mixing the second harmonic output of a ruby laser and the output of a tunable IR laser in ammonium dihydrogen phosphate (ADP) and potassium dihydrogen phosphate (KPD). At 60 mJ pulse energies in input beams, a 30 mJ output pulse energy is obtained using a 25-mm long ADP crystal. This corresponds to a 1.0 MW output pulse power and an average output power of 30 MW. UV powers achieved with a 50-mm long KDP crystal are 20% larger than those for the 25-mm long ADP crystal. Overall efficiencies up to 4.0% for converting ruby-laser output radiation to sum frequency radiation are found. The technique has a variety of applications including the study of photoionization.