Direct measurements of the duration and shape of picosecond pulses emitted by an optical parametric oscillator

An image-converter camera was used to determine the duration and shape of the output pulses of a singlepass optical parametric oscillator (OPO) composed of two KDP crystals pumped by the second harmonic of a passively mode-locked YAG:Nd³⁺ laser (the duration of the pump pulses was 25 ± 3 psec). It was found that under weak energy exchange conditions (when the energy conversion efficiency was ≤ 5%) the duration of the OPO output pulses decreased to 20 ± 2 psec, whereas in the case of a strong energy exchange (~15%) the duration of these pulses increased to 28 ± 5 psec.