COHERENT GENERATION OF FAR-INFRARED RADIATION FROM INP

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