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

Vanadium dioxide (VO₂) has been proposed as a phase-change material in tunable photonic and optoelectronic devices. In such devices, a thin layer of VO₂ 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 VO₂ 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 VO₂, the air/VO₂/Au structure can be considered as a Gires-Tournois resonant cavity whose maximum absorption wavelength can be tuned by adjusting the thickness of the VO₂ layer. In contrast, in the metallic phase of VO₂, 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.