Resonant optical second harmonic generation and mixing

TLDR

Optical resonance in KDP can greatly enhance second harmonic generation and mixing by coupling the harmonic power to transverse resonator modes. The study models both harmonic and fundamental resonances, incorporating double‑refraction effects to predict SHG behavior. Experiments with a low‑loss planoconcave KDP resonator achieved up to 500‑fold internal and 10‑fold external SHG enhancement, with fundamental power increased five‑fold, confirming the theoretical predictions.

Abstract

Experimental and theoretical results are described on the enhancement of optical second harmonic generation (SHG) and mixing in KDP by the use of optical resonance. Both resonance of the harmonic and of the fundamental are considered. Large enhancements are possible for resonators with low loss. Using a planoconcave harmonic resonator containing 1.23 cm of KDP, the authors achieved a loss < 4 percent per pass. This resulted in an enhancement of ∼ 500 times the harmonic power internal to the resonator and ∼ 10 times external to the resonator. When resonating, the fundamental enhancements of ∼ 5 were observed. The theory includes the effect of double refraction. This results in a coupling coefficient of the generated harmonic power to the transverse modes of the harmonic resonator. The experimental results are in substantial agreement with the theory.