  The functionalities of a wide range of optical and opto-electronic devices
are based on resonance effects and active tuning of the amplitude and
wavelength response is often essential. Plasmonic nanostructures are an
efficient way to create optical resonances, a prominent example is the
extraordinary optical transmission (EOT) through arrays of nanoholes patterned
in a metallic film. Tuning of resonances by heating, applying electrical or
optical signals has proven to be more elusive, due to the lack of materials
that can induce modulation over a broad spectral range and/or at high speeds.
Here we show that nanopatterned metals combined with phase change materials
(PCMs) can overcome this limitation due to the large change in optical
constants which can be induced thermally or on an ultrafast timescale. We
demonstrate resonance wavelength shifts as large as 385 nm - an order of
magnitude higher than previously reported - by combining properly designed Au
EOT nanostructures with Ge2Sb2Te5 (GST). Moreover, we show, through pump probe
measurements, repeatable and reversible, large amplitude modulations in the
resonances, especially at telecommunication wavelengths, over ps time scales
and at powers far below those needed to produce a permanent phase transition.
Our findings open a pathway to the design of hybrid metal PCM nanostructures
with ultrafast and widely tuneable resonance responses, which hold potential
impact on active nanophotonic devices such as tuneable optical filters, smart
windows, biosensors and reconfigurable memories.
