High-power LiIO3 optical parametric oscillator for infrared laser chemistry applications

A high-power singly resonant LiIO₃ crystal optical parametric oscillator (OPO) was developed for selective excitation of organic macromolecules. By using a high-Q resonator for λ = 1.3–1.7 μ and a large (~ 9 mm) pump beam diameter, a useful radiation energy higher than 0.1 J was obtained in the λ = 2.5–3.2 μ range in spite of the appreciable absorption of the crystal in this range. The results indicated that it would not be advisable to use crystals longer than 4 cm in the proposed system in view of mode locking and stimulated Raman scattering of resonant radiation from polaritons. An experimental investigation was made of the resonant effects of OPO radiation on OH group bonds in cellulose nitrate molecules.