Narrow-Linewidth Widely Tunable High-Pulse-Energy Mid-IR ZGP-based Parametric Source

Narrow-linewidth widely tunable mid-IR light source based on an optical parametric oscillator (OPO) and an optical parametric amplifier (OPA) was created for selective excitation of semiconductor THz luminescence and environmental monitoring. The compact OPO - OPA system based on ZnGeP
2
(ZGP) nonlinear crystals was pumped by high-energy $2.1-\mu \mathrm{m}$ $\mathrm{Ho}^{3+}$:YAG laser pulses with $\mathbf{1 0}$ - $\mathbf{1 0 0} \mathbf{~ H z}$ repetition rate. An OPO intracavity Fabry-Perrot filter based on a $30-\mu \mathrm{m}$ thickness Si-plate was used to achieve a narrow-linewidth output. The wide-band tuning within 3.4-5.5 $\mu \mathrm{m}$ was implemented using the active temperature control and orientation of the Si-plate and the ZGP crystal.