Thin-film VO2 submillimeter-wave modulators and polarizers

Submillimeter-wave modulators and switchable polarizers have been fabricated from VO2 thin films deposited on sapphire substrates. By passing electric current pulses through elements made from these films, the films can be thermally cycled through the insulator-to-metal transition that occurs in VO2 at about 65 °C. In the insulating state, the films are found to have negligible effect on the transmission at submillimeter wavelengths, while above the phase transition the transmission is strongly reduced by the free-electron effects characteristic of a metal. Other possible applications of such switchable VO2 elements include variable bandpass filters and diffraction grating beam-steering devices.