Parametric generation of picosecond radiation with high spectralQfactor and diffraction-limit divergence in a resonator by mode-locked pumping

A study was made of the resonator configuration of a picosecond optical parametric oscillator in which α -HIO 3 crystals were excited by phase-matched pumping. The configuration ensured a high energy efficiency of the process ( η E ≈10 % ) even at low pump intensities. The product of the pulse duration and the band width reached τΔν = 0.7 and the divergence of the radiation was 10 −3 rad, demonstrating the advantage of such resonator oscillators compared with the traveling-wave systems. The oscillator was pumped by a train of pulses of the second harmonic of a highly stable phosphate glass laser at a repetition frequency up to 2 Hz.