Intracavity sum-frequency mixing of a pulsed optical parametric oscillator for the efficient generation of continuously tunable ultraviolet radiation

Abstract

Summary form only given. Coherent all-solid-state light sources emitting broadly tunable UV radiation with high peak and average power are required by many applications. Such radiation can be generated by means of pulsed BBO or KTP optical parametric oscillators (OPOs) pumped by the harmonics of Q-switched Nd:YAG lasers and subsequent frequency upconversion such as second-harmonic generation (SHG) or sum-frequency mixing (SFM). High pump energies, however, are necessary to achieve reasonable UV pulse energies. It could be demonstrated, though, that the efficiency can be increased by intracavity doubling taking advantage of the high flux of the OPO signal inside the cavity. The generation of UV radiation by SHG with wavelengths below 330 nm, however, requires visible OPO radiation that can only be achieved with the third harmonic of Nd:YAG lasers as OPO pump. It is therefore more advantageous to pump the OPO with the more powerful second harmonic and to generate the UV radiation by SFM. Consequently, we devised a nanosecond OPO with intracavity sum-frequency mixing and compared different configurations such as linear and ring cavities.