High-power picosecond LiB3O5 optical parametric oscillators tunable in theblue spectral range

The paper reports on an experimental investigation and numerical analysis o f noncritically and critically phasematched LiB3O5 (LBO) optical parametric oscillators (OPOs) synchronously pumped by the third harmonic of a cw diod e-pumped mode-locked Nd:YVO4 oscillator-amplifier system. The laser system generates 9.0 W of 355-nm mode-locked radiation with a pulse duration of 7. 5 ps and a repetition rate of 84 MHz. The LBO OPO, synchronously pumped by the 355-nm pulses, generates a signal wave tunable in the blue spectral ran ge 457-479 nm. With a power of up to 5.0 W at 462 nm and 1.7 W at 1535 nm t he conversion efficiency is 74%. The OPO is characterized experimentally by measuring the output power (and its dependence on the pump power, the tran smission of the output coupler and the resonator length) and the pulse prop erties (such as pulse duration and spectral width). Also the beam quality o f the resonant and nonresonant waves is investigated. The measured results are compared with the predictions of a numerical analysis for Gaussian lase r and OPO beams. In addition to the blue-signal output visible-red 629-nm r adiation is generated by sum-frequency mixing of the 1.535-mum infrared idl er wave with the residual 1.064-mum laser radiation. A power of 1.25 W of 1 .535-mum idler radiation and 5.7 W of 1.064-mum laser light generated a red 629-nm output power of 2.25 W.