Controlling light on the nanoscale: ultrafast plasmonics and phase change functionality

Abstract

The first experimental confirmation that femtosecond plasmon pulses can be generated, transmitted and modulated along a metal/dielectric waveguide is achieved. The ultrafast optical modulation of plasmons is accomplished by optical excitation of the aluminium plasmonic waveguide using 200 fs optical pulses at wavelengths near the aluminium’s interband absorption resonance (lambda ~ 800 nm). The demonstrated modulation rates are at least five orders of magnitude faster than provided by existing technologies. Modulation depths ~30% are achieved at pump fluences of ~10 mJ/cm². The first quantitative analysis of femtosecond surface plasmon polariton pulse propagation effects in several metal/dielectric waveguides is presented. It is found that femtosecond plasmon pulses will reshape because of group velocity and loss dispersion. These dispersions have substantial impact on shape, intensity and retardation of plasmon pulses. For instance, propagation of 700 nm, 10 fs plasmon pulses on gold surface results in 155% pulse broadening on a plasmon decay length. The first experimental confirmation that stable silver/gallium lanthanum sulphide interfaces support plasmon propagation is presented. It is shown for the first time that plasmonic properties can be effected by structural changes in the chalcogenide layer, providing high contrast plasmonic modulations. Moreover it is shown experimentally that photo-induced changes by white light optical illumination with intensities of 630 mW/cm2 of chalcogenide glass results in plasmonic modulations of up to 3% in a silver/gallium lanthanum sulphide interface. The first experimental electro-optic switch of a chalcogenide hybridized metamaterial is achieved on the nanoscale. The transition between amorphous and crystalline forms of chalcogenide brings ~140 nm resonance shift of the hybrid structure. Transmission modulation with a contrast ratio of 4:1 in a device of 370 nm thickness is demonstrated at wavelength of 1200 nm. The spectral band of the high contrast modulation can be engineered by design and located within the entire transparency range of the chalcogenide glass.

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Identifiers

ORCID for N.I. Zheludev: orcid.org/0000-0002-1013-6636

ORCID for Kevin MacDonald: orcid.org/0000-0002-3877-2976

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