Optically controlled microstrip load and stub on silicon substrate

In this paper we report the modeling and experimental measurements for optical control of a microstrip load and λ_g/4 stub fabricated on high-resistivity silicon substrate. We present the basic circuit model of a photoinduced or optical load created by a laser spot at the end of an open microstrip line. The modeled optical load has been used to simulate reflections at open microstrip line terminated by the optical load. The results obtained by both simulation and measurement show than an optical load created at the open termination of a microstrip line can control the reflection parameter of the line. A similar optical load created at the end of an open λg/4 stub on a microstrip line has been shown to control the transmitted power at the design frequency. The measurement results compare well with those predicted by both a simple circuit simulation and a simulation carried out on the Ansoft Maxwell simulator using a termination obtained by an equivalent circuit model of the optical load.