Parametric superluminescence in a ZnGeP2 crystal with temperature tuning and pumping by an erbium laser

Temperature tuning of IR traveling-wave parametric generation (parametric superluminescence) has been studied in a ZnGeP₂ crystal. A Q-switched Er:YSGG laser (λ = 2.79) with active mode locking was used. Part of a wavelength interval near the degeneracy point which is inaccessible in the case of angle tuning can be reached in the case of temperature tuning. The beam walk-off and deviation from alignment which are unavoidable in the case of angle tuning can thus be eliminated. This result is attributed to a change in the birefringence of the crystal and of its refractive index with increasing temperature.