Tunable 7–12-µm optical parametric oscillator using a Cr,Er:YSGG laser to pump CdSe and ZnGeP_2 crystals

A CdSe optical parametric oscillator (OPO) pumped by a 2.79-$\mathit{\mu }\mathrm{m}$, Cr,Er:YSGG laser yielded a 59% signal-plus-idler slope efficiency ($\eta$), a total idler output of 1.2–2.4 mJ between 8.5 and 12.3 $\mathit{\mu }\mathrm{m}$, and an idler beam that was 2.2–2.5 times the diffraction limit. A ZnGeP₂ OPO operated with a lower threshold, $\eta =29\%$, and a forward idler output of 0.7–2.4 mJ from 6.9 to 9.9 $\mathit{\mu }\mathrm{m}$. The signal and idler bandwidths were typically 4 ${\mathrm{cm}}^{-1}$ for each OPO.