EFFICIENT ULTRAVIOLET LIB3O5 OPTICAL PARAMETRIC OSCILLATOR

We report what is to our knowledge the first optical parametric oscillator (OPO) generating coherent laser radiation with high optical-to-optical conversion efficiency in the near ultraviolet. The OPO, pumped at 307.8 nm by a pulsed injection-seeded XeCl excimer laser, employs a crystal of LiB3O5 in a noncritical phase-matching geometry to generate tunable output over the range 381-387 nm in the near ultraviolet and 1.5-1.6-mu-m in the near infrared. We report internal energy conversion efficiencies as high as 28% for the signal wave at 385.5 nm and 7% for the idler wave at 1.53-mu-m, leading to a total internal conversion efficiency of 35%. Studies of oscillation threshold, external and internal conversion efficiency, spectral linewidth, and temporal variation of output pulses are also reported. Temperature tuning of the LiB3O5 OPO under the noncritical phase-matching condition is demonstrated for the first time to our knowledge.