Abstract-Terahertz generation by optical rectification in chalcopyrite crystals ZnGeP2, CdGeP2 and CdSiP2

Herath P. Piyathilaka, Rishmali Sooriyagoda, Vikum Dewasurendra, Matthew B. Johnson, Kevin T. Zawilski, Peter G. Schunemann, and Alan D. Bristow

Fig. 1 (a) Photographs of the polished CdGeP2 (CGP), ZnGeP2 (ZGP) and CdSiP2 (CSP) crystals from top to bottom. Visible light is reflected from the CGP. (b) Tauc plot for absorption edges using direct-gap normalization.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-12-16958

Optical rectification of near-infrared laser pulses generates broadband terahertz radiation in chalcopyrite crystals CdGeP2, ZnGeP2 and CdSiP2. 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 CdGeP2 produced the strongest emission at telecoms wavelengths, while CdSiP2 is generally the strongest source. Pump-intensity dependence provides the nonlinear coefficients for each crystal.

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