Active Control of Surface Plasmon Waveguides with a Phase Change Material

The ability to manipulate light propagation at the nanoscale is of vital importance for future integrated photonic circuits. In this work we exploit the high contrast in the optical properties of the phase change material Ge₂Sb₂Te₅ to control the propagation of surface plasmon polaritons at a Au/SiO₂ interface. Using grating couplers, normally incident light at λ = 1.55 μm is converted into propagating surface plasmons on a Au waveguide. Single laser pulses (λ = 975 nm) are applied to a thin film of Ge₂Sb₂Te₅ placed on top of the device, which, upon transition from its amorphous to crystalline structural phase, dramatically increases both its refractive index and absorption coefficient, thus inhibiting propagation of the plasmonic mode. This effect is investigated for different interaction lengths between the phase change material and the Au waveguide, and contrast values in the transmitted intensity up to several tens of percents are demonstrated.