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 semiconductor is spatially biased with a static electric field of period ${\lambda }_0$, the laser pulse acts as a fast switch and generates a periodic current. 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 tuned by adjusting ${\lambda }_0$, the wafer-wall separation, and/or the carrier density. In the absence of collisional damping, ${\mathit{N}}_0$ periods of the static bias electric field will generate ${\mathit{N}}_0$ periods of radiation. Under idealized conditions, the maximum electric field of the radiation is equal to the applied static field and the maximum efficiency of converting the static electric field energy to electromagnetic energy is 30%. In practice for typical parameters, tunable electromagnetic radiation can be generated with wavelengths in the 50–500-μm range, pulse durations in the picosecond or subpicosecond range, and peak powers on the order of 100 W. © 1996 The American Physical Society.