Terahertz generation by optical rectification in chalcopyrite crystals ZnGeP, CdGeP and CdSiP.

Optical rectification of near-infrared laser pulses generates broadband terahertz radiation in chalcopyrite crystals CdGeP, ZnGeP and CdSiP. The emission is characterized using linear-polarized excitation from 0.8 eV to 1.55 eV (1550 nm - 800 nm). All three crystals are (110)-cut and polished to 0.5 mm, thinner than the coherence length across most of the excitation photon energy range, such that they all produce a bandwidth ~2.5 THz when excited with ~100 fs pulses. It is found that CdGeP produced the strongest emission at telecoms wavelengths, while CdSiP is generally the strongest source. Pump-intensity dependence provides the nonlinear coefficients for each crystal.