Parametric conversion of the third harmonic of a neodymium laser in KDP crystals by injection of a low-power signal

An investigation was made of the efficiency of the vector parametric conversion of the third harmonic of an Nd laser in KDP crystals by injection of a low-power λ = 1.054 μm signal into difference-frequency radiation with λ_s = 0.527 μm. The maximum efficiency of conversion relative to the λ = 0.351 μm radiation was close to the calculated value and reached 36%. Experiments indicated that 70% of the subharmonic radiation (λ_s = 0.527 μm) was within a solid angle of 10 ^– 4 rad. Experiments and calculations confirmed that parametric conversion of the third harmonic of an Nd laser in a KDP crystal to the range 0.47 < λ_s < 0.527 μm by injection of a weak infrared signal (with a divergence of 10 ^– 4 rad) into the crystal could be used to increase the efficiency to 40–50% (or 20–25% relative to the Nd laser radiation) and still retain the high directionality of the radiation.