Dielectric waveguide structures with surface controlled impedance

In the K/sub a/ frequency band, we have fabricated and tested dielectric guide structures and resonators that are coated either by thin metal or by semiconductor light-sensitive film. Such films enable the design of a number of passive and active elements over the millimeter-wave frequency range. We have also developed a lumped parallel resonator with a controlled Q-factor, in which a light-sensitive KdS film is used as active resistor. Resonator inductor and capacitor were implemented in the form of a thin metal coating over the dielectric guide. When exposed to light, these compounds reduce their resistance as a result of which surface impedance changes.