Tunable near-infrared and visible all-solid-state optical parametric oscillator amplifier system based on potassium titanyl phosphate crystal

We present the design details and performance characteristics of a low-energy all-solid-state near-infrared optical parametric oscillator amplifier (OPOA). The pump source is a laser diode (LD) pumped frequency-doubled Nd:YAG laser with a single mode energy of 4 mJ in 8 ns, 50 Hz pulses. The OPOA system, based on potassium titanyl phosphate (KTP) crystal, features a low pump energy threshold at 532 nm of less than 0.4 mJ, broad tunability from 750 to 1040 nm for the signal and a conversion efficiency of 27% at 920 nm. External cavity second harmonic conversion of the idler to visible green-red light in a type II KTP crystal and of the signal to visible blue-green light in a type I BBO crystal was performed with efficiencies up to 10%. We have used the near-infrared output for wavelength-dependent fluorescence lifetime studies in ytterbium-doped laser materials. We have also used the second harmonic wavelengths between 565-600 nm to measure the transmission of Nd:YAG in a preliminary experiment to demonstrate the utility of the system.