TUNABLE DOUBLY RESONANT OPTICAL PARAMETRIC OSCILLATOR WITH LBO AND KTP CRYSTALS PUMPED BY 2ND-HARMONIC OF A NANOSECOND ND-YAG LASER

We compare two types of optical parametric oscillators (OPO's) with LB O and KTP crystals, pumped with a frequency doubled Q-switched Nd:YAG laser. The threshold pump power density near degeneracy was found to b e 29 MPW/cm(2) for the pulsed doubly resonant oscillator (DRO) with LB O, and 5.7 MW/cm(2) for the DRO with KTP. The DRO was continuously tun ed in the near infrared by rotation of LBO and KTP crystals. The full width at half-maximum (FWHM) linewidth of the signal radiation emitted by DRO-LBO at 998 nm was 10 nm, and 0.65 nm for DRO-KTP at 1052.6 nm.