Giant nonlinear response of terahertz nanoresonators on VO2 thin film

We report on an order of magnitude enhanced nonlinear response of vanadium dioxide thin film patterned with nanoresonators – nano slot antennas fabricated on the gold film. Transmission of terahertz radiation, little affected by an optical pumping for the case of bulk thin film, can now be completely switched-off: ΔT/T≈-0.9999 by the same optical pumping power. This unprecedentedly large optical pump-terahertz probe nonlinearity originates from the insulator-to-metal phase transition drastically reducing the antenna cross sections of the nanoresonators. Our scheme enables nanoscale-thin film technology to be used for all-optical switching of long wavelength light.