COHERENT GENERATION OF FAR-INFRARED RADIATION FROM INP

We have studied the production of far-infrared (FIR) radiation in electric-field-biased [111] InP illuminated by 120-fs 770-nm laser pulses. The electric field is applied without electrodes: a 500-fs pulse of single-cycle radiation from a GaAs photoconducting switch acts as the bias. The observed FIR energy varies with the orientation of the InP sample, the laser polarization, and the direction and the magnitude of the bias field. These dependencies are used to place constraints on the nonlinear susceptibility tensor that is responsible for FIR generation.