  Surface plasmon polaritons can substantially reduce the sizes of optical
devices, since they can concentrate light to (sub)wavelength scales. However,
(sub)wavelength-scale electro-optic plasmonic switches or modulators with high
efficiency, low insertion loss, and high extinction ratios remain a challenge
due to their small active volumes. Here, we use the insulator-metal phase
transition of a correlated-electron material, vanadium dioxide, to overcome
this limitation and demonstrate compact, broadband, and efficient plasmonic
switches with integrated electrical control. The devices are micron-scale in
length and operate near a wavelength of 1550 nm. The switching bandwidths
exceed 100 nm and applied voltages of only 400 mV are sufficient to attain
extinction ratios in excess of 20 dB. Our results illustrate the potential of
using phase transition materials for highly efficient and ultra-compact
plasmonic switches and modulators.
