VO₂ based polarization-independent dual-wavelength plasmonic switches using U and C shaped nanostructures

We have proposed vanadium dioxide (VO₂) based polarization-independent dual-wavelength plasmonic switches using a periodic combination of U and C shaped gold nanostructures on a gold coated silicon dioxide (SiO₂) substrate with a thin VO₂ film as spacer between the nanostructures and the underlying substrate. A spatial offset between the two nanostructures is taken such that high switching efficiency is obtained simultaneously at two wavelengths for all polarization angles of incident light. The switching mechanism is based on the transformation of the phase change material, VO₂, from its monoclinic semiconductor state to its tetragonal metal state when exposed to an external stimulus. This transformation leads to a significant change in the optical behavior of the proposed switch, leading to an effective transition from ON to OFF state. Finite difference time domain (FDTD) modelling shows that the proposed switches are capable of achieving a high extinction ratio of ~ 20 dB at two wavelengths-1560 nm and 2130 nm-for incident light with any polarization angle. To demonstrate the spectral tunability of switching wavelengths, the optimization of the geometrical parameters is also carried out. These switches can be employed in telecommunication networks, optical communications, and integrated photonic circuits.