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Far-field excitation of single graphene plasmon cavities with ultracompressed mode volumes

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Science  12 Jun 2020:
Vol. 368, Issue 6496, pp. 1219-1223
DOI: 10.1126/science.abb1570

Light under compression

The ability to confine light to volumes much smaller than the wavelength produces high electromagnetic fields that can then be exploited in chemical and biological sensing and detection applications. Using silver nanocubes placed on a graphene surface, Epstein et al. developed a single, nanometer-scale acoustic graphene plasmon cavity device that can confine mid-infrared and terahertz radiation with mode volume confinement factors of 5 × 10–10. With the response being dependent on the size of the nanocube and electrically tunable, the results demonstrate a powerful platform with which to develop sensors in what has been a challenging wavelength regime where molecular fingerprints reside.

Science, this issue p. 1219

Abstract

Acoustic graphene plasmons are highly confined electromagnetic modes carrying large momentum and low loss in the mid-infrared and terahertz spectra. However, until now they have been restricted to micrometer-scale areas, reducing their confinement potential by several orders of magnitude. Using a graphene-based magnetic resonator, we realized single, nanometer-scale acoustic graphene plasmon cavities, reaching mode volume confinement factors of ~5 × 10–10. Such a cavity acts as a mid-infrared nanoantenna, which is efficiently excited from the far field and is electrically tunable over an extremely large broadband spectrum. Our approach provides a platform for studying ultrastrong-coupling phenomena, such as chemical manipulation via vibrational strong coupling, as well as a path to efficient detectors and sensors operating in this long-wavelength spectral range.

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