ALL-SOLID-STATE TUNABLE KTP OPTICAL PARAMETRIC OSCILLATOR AMPLIFIER SYSTEM

We present the performance charateristics of a low-energy all-solid-st ate near-infrared optical parametric oscillator amplifier (OPOA). The pump source is a laser diode (LD) pumped frequency-doubled Nd:YAG lase r with a single mode energy of 4 mJ in 8 ns, 50 Hz pulses. The OPOA sy stem, based on a potassium titanyl phosphate (KTP) crystal, features a low pump energy threshold at 532 nm of less than 0.4 mJ, broad tunabi lity from 750 to 1040 nm for the signal, and a conversion efficiency o f 27 % at 920 nm. The bandwith at 960 nm was reduced from that of the free-running mode (>100 GHz) to less than 150 MHz by the simultaneous injection seeding of the pump laser and the OPOA, and this is close to the Frourier transform limit for the 4 ns output pulses. The OPOA has a potential tunability of over 60 nm from 915 - 975 nm which is deter mined by its external cavity-grating-tuned-diode seed laser. The exter nal cavity second-harmonic conversion of the idler to visible green-re d light in type II KTP crystal and of the signal to visible blue-green light in type I BBO crystal was performed with efficiencies up to 10 %. We used the near-infrared output for wavelength-dependent fluoresce nce lifetime studies in yitterbium-doped laser materials. We also used the second harmonic wavelengths between 565 - 600 nm to measure the t ransmisssion of Nd:YAG in a preminary experiment to demonstrate the ut ility of the system.