Abstract
While plasmons in noble metal nanostructures enable strong light-matter interactions on commensurate length scales, the overabundance of free electrons in these systems inhibits their tunability by weak external stimuli. Countering this limitation, the linear electronic dispersion in graphene endows the two-dimensional material with both an enhanced sensitivity to doping electron density, enabling active tunability of its highly confined plasmon resonances, and a very low electronic heat capacity that renders its thermo-optical response extraordinarily large. Here we show that these properties combined enables a substantial optical modulation in graphene nanostructures from the energy associated with just one of their supported plasmons. We base our analysis on realistic, complementary classical and quantum-mechanical simulations, which reveal that the energy of a single plasmon, absorbed in a small, moderately doped graphene nanoisland, can sufficiently modify its electronic temperature and chemical potential to produce unity-order modulation of the optical response within subpicosecond time scales, effectively shifting or damping the original plasmon absorption peak and thereby blockading subsequent excitation of a second plasmon. The proposed thermo-optical single-plasmon blockade consists in a viable ultralow power all-optical switching mechanism for doped graphene nanoislands, while their combination with quantum emitters could yield applications in biological sensing and quantum nano-optics.
Highlights
The ability of plasmons –the collective oscillations of conduction electrons– to intensify the electromagnetic field of light has stimulated fertile research efforts in nonlinear plasmonics to control light by light on the nanoscale.[1]
We base our analysis on realistic, complimentary classical and quantum-mechanical simulations, which reveal that the energy of a single plasmon, absorbed in a small, moderately-doped graphene nanoisland, can sufficiently modify its electronic temperature and chemical potential to produce unity-order modulation of the optical response within subpicosecond timescales, effectively shifting or damping the original plasmon absorption peak and thereby blockading subsequent excitation of a second plasmon
Following excitation by an ultrafast optical pump, graphene plasmons decay on typically longer timescales than their noble metal counterparts into energetic electrons and holes,[23,29] which subsequently thermalize on ultrafast timescales.[25,26]
Summary
The ability of plasmons –the collective oscillations of conduction electrons– to intensify the electromagnetic field of light has stimulated fertile research efforts in nonlinear plasmonics to control light by light on the nanoscale.[1].
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