Tunable near-infrared Gires-Tournois resonators based on vanadium dioxide on gold film.

Vanadium dioxide (VO) has been proposed as a phase-change material in tunable photonic and optoelectronic devices. In such devices, a thin layer of VO is typically deposited on metallic or insulating surfaces. In this Letter, we report the reflectance spectra of a subwavelength structure consisting of a thin layer of VO deposited on a gold film in the near-infrared spectral range, particularly near the wavelength of 1550 nm, which is significant for telecommunication applications. Our results indicate that in the insulating phase of VO, the air/VO/Au structure can be considered as a Gires-Tournois resonant cavity whose maximum absorption wavelength can be tuned by adjusting the thickness of the VO layer. In contrast, in the metallic phase of VO, the reflectance of the structure increases by an amount of the order of a few tens of units. The proposed structure can prospectively lead to new design concepts in tunable photonic and optoelectronic devices.