High-efficiency picosecond parametric superradiance emitted by a ZnGeP2crystal in the 5–6.3 µ range

Highly efficient (quantum efficiency 17%) parametric superradiance was generated in a nonlinear ZnGeP 2 crystal of length 4.2 cm pumped by single (of energy ∼1 mJ) ultrashort pulses ( τ = 150 psec) from an erbium laser ( λ = 2.79 µ ). High-power (∼1 MW) continuously tunable infrared radiation of wavelengths 5–5.3 and 5.9–6.3 µ was obtained. The energy and angular tuning characteristics, line width, divergence, and gain of this superradiance were determined. The nonlinear coefficient d 36 was found for ZnGeP 2 . Depletion of the laser pumping had to be allowed for already for parametric superradiance efficiency of just 0.1%.