Phase-change metamaterials combine the sharp resonant dispersions afforded by metamaterials with the optical switching characteristics of phase-change chalcogenides to create a high-contrast, non-volatile planar optical modulator. Spectroscopic ellipsometry was used to accurately determine the highly-contrasting complex dielectric functions of the amorphous and crystalline states of GST, an amorphous chalcogenide. This data was then used to model a phase-change metamaterial hybrid device in both phases,which showed a large wavelength shift in resonant spectral features on crystallisation of the chalcogenide layer. Femtosecond pulse-induced crystallisation and amorphisation of thin films of GST was shown to be possible, and the crystalline fraction in the material was shown to be continuously tunable. Femtosecond pulses were then used to reversibly switch a phase-change metamaterial device to modulate the trapped mode resonance. Modelling of an all-dielectric phase-change metamaterial structure indicated that larger optical modulation may be realised by changing the phase of the resonant structure itself.
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