Improvement in the conversion efficiency of pulsed optical parametric oscillators using external signal injection

An experimental and theoretical investigation was made of the influence of an external dye laser signal on the power and threshold characteristics of a singly resonant optical parametric oscillator utilizing a lithium niobate crystal pumped by the second harmonic of a YAG:Nd laser. When the pulse power of the injected signal was only a few tens of milliwatts, the maximum efficiency of the optical parametric oscillator (OPO) was more than doubled and the unsaturated signal gain reached 10⁶. It was established that the injected signal had a particularly strong influence on the OPO output characteristics at threshold pumping levels.