The role of optical rectification in the generation of terahertz radiation from GaBiAs

We report on a detailed study of the emission of terahertz-frequency electromagnetic radiation from layers of GaBiyAs1−y (0≤yBand (001) GaAs substrates. We measure two orthogonally polarized components of the terahertz radiation emitted under excitation by ultrashort near-infrared laser pulses in both transmission and reflection geometries as a function of the crystal rotation about its surface normal as well as the effect of in-plane magnetic field and pump fluence on the terahertz emission. We conclude that the principal mechanism for terahertz generation is via optical rectification rather than transient currents.