EFFICIENT GENERATION OF CONTINOUSLY TUNABLE ULTRAVIOLET RADIATION BY INTRA-CAVITY SUM FREQUENCY MIXING IN PULSED OPTICAL PARAMETRIC OSCILLATORS

摘要

Continuously tunable UV radiation was efficiently generated by intra-cavity mixing either the signal or the idler wave of a nanosecond KTP-OPO with the second or third harmonic of an injection-seeded Q-switched Nd: YAG pump laser. Starting from a pump energy of 410mJ at 1064nm a maximum energy of 19.5mJ/pulse at 320nm was achieved. This corresponds to a conversion efficiency of 9.5% from the second harmonic, or 4.8% from the fundamental of the Nd:YAG laser to the UV. The investigated set-ups could be tuned in the range of 234-325nm. The possible theoretical tuning range is as broad as 225-350nm. The divergence of the UV-beam was less than 0.7mrad. The pulse width was 5-6ns and the energy stability was 1% rms. The high overall efficiency make these devices promising for applications such as remote sensing in the UV, particularly, when diode-pumped solid-state lasers will soon serve as pump.