This is a 1992 RIA Award. The objective of this proposal is to generate intense terahertz bandwidth microwave radiation pulses form semiconductor photovoltaic devices, and apply it to the study of transient electric and optoelectronic properties of dielectric materials under an extremely high field with a contactless approach. The technique consists of using a picosecond laser beam to illuminate semiconductor solar cells, and generates electron magnetic radiation produced by rapid current transients due to optical injection of free carriers into the static electric field. The radiation is directional and diffraction-limited. Since the microwave energy comes mainly from the static energy stored in the semiconductor devices rather than from the incident laser energy, with the proper design of device structure and high external bias, the total power of the radiation can well exceed the incident power of the laser beam. A study of the power scaling properties suggests that the scaling up to GigaWatt peak powers is feasible in semiconductor photovoltaic structure sizes up to 100 cm2. It is possible to study transient electric and optoelectric properties of dielectric materials under an extremely high field with a contactless approach, and to pursue a new subject: nonlinear microwave measurement of dielectric materials.
