An Optically-Triggered Switchable Mid-Infrared Perfect Absorber Based on Phase-Change Material of Vanadium Dioxide

Abstract

Switchable nanoscale devices can be implemented in heterostructures that integrate plasmonic nanostructures with functional active materials and hence hold great potential for nanoscale-integrated circuits. The phase-change material of vanadium dioxide (VO2) has reversibly switchable optical/electrical properties and huge contrast in its refractive index in the infrared spectral range between insulator and metallic states. In this work, we numerically demonstrate all-optical manipulation of switchable absorption effect using the heterostructure incorporating the plasmonic resonance of Au nanoantennas with vanadium dioxide. Compared with the planar control device (without Au nanoantennas), the proposed design exhibits a pronounced resonant field enhancement as well as polarization-insensitive and omnidirectional absorption response. Meanwhile, the proposed device shows a large switching contrast (from ~ 99.9 to ~ 10% in absorption efficiency) at the mid-infrared wavelength of 3609 nm. Interestingly, the resonance of the proposed device can be continuously tuned by varying the side length of the antennas or governing the metallization level of vanadium dioxide layer. The photothermal mechanism is further investigated by numerical model calculations, indicating that the resonant, antenna-mediated local heating occurs on a sub-nanosecond time scale of 0.26 ns under a quite low incident intensity of 1.9 × 106 W/m2, which is about 12.5 times reduced with respect to that of control device. Therefore, the hybrid strategy of plasmonic antennas and vanadium dioxide provides a conceptual framework of switchable metamaterials for actively steering in ultrafast, energy-efficient electronic and photonic devices.