Simple, high-performance type II β-BaB_2O_4 optical parametric oscillator

Abstract

A visible/near-IR optical parametric oscillator (OPO) based on type II phase matching in β-BaB2 O4 (BBO) is described. Pumped at 355 nm, this OPO covers 410–2500 nm completely with a single set of standard Nd:YAG cavity optics. The output efficiency is >25%, the linewidth of the OPO is narrower than 1–2 cm-1 without the use of gratings or etalons, and the signal-beam divergence is <400 µrad. Three type I BBO doubling crystals are used to extend the tuning range from 208 to 415 nm. Doubling efficiencies as high as 40% are easily obtained. The reasons for the high doubling and overall system efficiency are discussed.