Generation of broadband terahertz pulses via optical rectification in a chalcopyrite CdSiP₂ crystal

We report on the generation of broadband (0.07-6 THz) terahertz (THz) radiation via optical rectification in a ⟨110⟩  CdSiP₂ (CSP) crystal pumped by a 50 fs, 780 nm central wavelength optical pulse. By measuring the THz phase refractive index and the optical pump group refractive index, good phase matching can be achieved for a crystal thickness ≲200  μm. Due to this crystal's high second order nonlinearity and low absorption losses, it is envisioned that THz generation from CSP could be further enhanced by confining the optical pump pulse to sub-wavelength waveguides.