Efficient Polarization Modulation by a Phase Change Material on Metal

The polarization of light interacting with a layer of vanadium dioxide (VO2) undergoing phase transition is known to change due to large changes in the material’s refractive index. While this effect is promising for optical modulation applications, the usual VO2 films on dielectric substrates tend to offer limited tenability in terms of wavelength and angle of incidence. In this paper, we show that metallic under-layers greatly enhance the performance by widening the spectral range to include visible wavelengths, by increasing the polarization modulation amplitude, and by widening the range of workable incidence angles. The imaginary part of the refractive index in the metallic layer is found to increase the relative phase shifts between s- and p-components of polarization as well as increasing the reflectance.