Photonically tuned patch and dipole millimetre wave arrays using selectively doped semiconductor wafers

We present results from a previous study into the manipulation of the transmission response arising from an array of doped elements within a semiconductor wafer. If a periodic array is formed by doping, within a semiconductor slab of suitable resistivity, then a resonant effect is produced when a plane wave is incident on the sample. The performance of this array can be very close to that of a conventional frequency selective surfaces (FSS) provided the doping levels are high enough. Results are presented from a new study we have carried out to investigate the tuning effect of an incident photonic beam on a predetermined array of doped elements within a semiconductor wafer. When photons of suitable wavelength are incident on a semiconductor the photoconductive nature of the semiconductor renders it more conducting than in the dark state and we use this property in this study. An optical mask is used whereby the wafer is only exposed to the optical beam through the transparent regions of the mask. In this way the performance of the array can be controlled and tuned over a range determined by the dimensions of the mask used. We have previously used this technique to successfully generate inductive grid arrays within a silicon wafer