THz generation in InAs
We have observed strong terahertz (THz) emission from the face of p-type InAs when it is illuminated by ultrashort (<12 fs) pulses of near-infrared radiation. As the crystal is rotated about the surface normal, there are two maxima per rotation, suggesting optical rectification plays a role in the emission process. This holds whether the angle of incidence is 45°, most convenient for technical application, or 75°, the Brewster angle, where the THz output is strongest. The power of the THz radiation varies approximately quadratically with the pump power. The data are consistent with photocurrent surge being the main mechanism of THz emission. We have found that the p-type InAs produces about two orders of magnitude more power than a standard unbiased THz emitter, 1-mm thick ZnTe.