Recently discovered extraordinary transmission of light through a thick metal plate perforated by regular hole array is in this paper studied for switching applications. Although this extraordinary transmission effect was first found in optical regime, it also occurs at microwave frequencies. In this study transmission of microwave radiation at normal incidence is theoretically studied through a semiconductor layer covered on both sides by a metal plate with regular hole array. At first, an analytical model for a metal plate perforated by dense regular hole array is presented. The metal hole array plate is modeled as a frequency dependent lumped inductance applicable for transmission-line modeling. Secondly, the properties of the semiconductor layer are considered. Silicon is a photoconducting material whose conductivity increases when exposed to optical illumination. With enough high optical illumination the perforated metal plate backed by semiconductor slab is like a metal conductor, and transmission through the structure is negligible. The whole structure, two perforated plates and the slab between them, is modeled using transmission-line techniques. The reflection and transmission coefficients are presented. Because the properties of the semiconductor slab can be controlled with optical illumination, we have optically controlled switch device for microwave transmission.