Highly efficient visible and infrared β-BaB2O4 optical parametric oscillator with pump reflection

We report the successful operation of a highly efficient visible and near-infrared optical parametric oscillator (OPO) that uses β-BaB2O4 as the nonlinear medium and is pumped at 354.7 nm. An energy conversion efficiency of 41% corresponding to a quantum conversion efficiency as high as 57% has been achieved in a 10-mm-long crystal. Pump depletion is estimated to be 70% or so. This OPO can generate an average output power to 507 mW at 490 nm and can be continuously tuned from 415 to 2411 nm. The reverse frequency conversion process has also been observed in the OPO. The reason for its high efficiency is discussed.