Microwave measurements of effective dielectric constant of semiconductor waveguides via periodic-structure photoexcitation

In this paper a new method for measurements of the effective dielectric constant of layered or full-substrate semiconductor waveguides at microwave frequencies is presented. The light-induced generation of a photoconductivity grating within the excited waveguide section is utilized. Incoming swept-frequency signals produce a stop-band reflection spectrum which exhibits a dominant major-lobe peak value at the grating center frequency. The effective dielectric constant is calculated from a simple analytical expression by substituting the measured center frequency. Theoretical background, error estimation, and an example are presented.