Light-Controlled MMW Beam Scanner

We describe a novel beam scanning method for microwave or MMW radiation. The method employs a semiconductor or photoconductor wafer in which a spatially varying density of charge carriers is created by optical injection. The induced electron/hole plasma of free carriers alters the dielectric constant of the wafer locally and thereby attenuates incident MMW radiation. A spatially varying density of free carriers can be made to diffract the incident MMW radiation into a beam. Because the wafer responds rapidly to changes in conditions which produce carriers, it is possible to rapidly change the diffractive conditions and thus scan the beam.