Intracavity difference-frequency mixing of optical parametric oscillator signal and idler pulses in BaGa₄Se₇

An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 μm pumped Rb:PPKTP optical parametric oscillator in BaGa₄Se₇. In this way, a pulse energy of ∼0.71  mJ is generated at ∼7  μm for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb:PPKTP crystal.