Attainment of high efficiencies in optical parametric oscillators

Major practical requirements relevant to achieving high conversion efficiencies in optical parametric oscillators have been identified. In particular, an experimental comparison has been made between critically and noncritically phase-matched geometries in beta-barium borate (BBO) and lithium triborate (LBO), respectively, when they are pumped by an excimer laser at 308 nm. We report pump depletions of 40% in LBO and 50% in BBO when 385- and 1540-nm radiation is parametrically generated. Pump depletions of 64% have been obtained in BBO when 540- and 700-nm radiation is generated. Optimization of external efficiencies has been studied, and values of 30% have been obtained in LBO by resonating the low-energy wave.