RADIATION GENERATION BY PHOTOSWITCHED, PERIODICALLY BIASED SEMICONDUCTORS

A laser pulse, propagating nearly parallel to the surface of a planar semiconductor wafer, will generate electron-hole pairs. If the semicon ductor is spatially biased with a static electric held of period lambd a(0), the laser pulse acts as a fast switch and generates a periodic c urrent. The rapid switching of the current generates radiation, which propagates along the surface and can be confined by a conducting wall placed parallel to the wafer. The wavelength of the radiation can be t uned by adjusting lambda(0), the wafer-wall separation, and/or the car rier density. In the absence of collisional damping, N-0 periods of th e static bias electric field will generate N-0 periods of radiation. U nder idealized conditions, the maximum electric field of the radiation is equal to the applied static held and the maximum efficiency of con verting the static electric field energy to electromagnetic energy is 30%. In practice for typical parameters, tunable electromagnetic radia tion can be generated with wavelengths in the 50-500-mu m range, pulse durations in the picosecond or subpicosecond range, and peak powers o n the order of 100 W.