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Hybrid surface-phonon-plasmon polariton modes in graphene/monolayer h-BN heterostructures.
Brar, Victor W,Jang, Min Seok,Sherrott, Michelle,Kim, Seyoon,Lopez, Josue J,Kim, Laura B,Choi, Mansoo,Atwater, Harry American Chemical Society 2014 NANO LETTERS Vol.14 No.7
<P>Infrared transmission measurements reveal the hybridization of graphene plasmons and the phonons in a monolayer hexagonal boron nitride (h-BN) sheet. Frequency-wavevector dispersion relations of the electromagnetically coupled graphene plasmon/h-BN phonon modes are derived from measurement of nanoresonators with widths varying from 30 to 300 nm. It is shown that the graphene plasmon mode is split into two distinct optical modes that display an anticrossing behavior near the energy of the h-BN optical phonon at 1370 cm(-1). We explain this behavior as a classical electromagnetic strong-coupling with the highly confined near fields of the graphene plasmons allowing for hybridization with the phonons of the atomically thin h-BN layer to create two clearly separated new surface-phonon-plasmon-polariton (SPPP) modes.</P>
Electronically Tunable Perfect Absorption in Graphene
Kim, Seyoon,Jang, Min Seok,Brar, Victor W.,Mauser, Kelly W.,Kim, Laura,Atwater, Harry A. American Chemical Society 2018 NANO LETTERS Vol.18 No.2
<P>The demand for dynamically tunable light modulation in flat optics applications has grown in recent years. Graphene nanostructures have been extensively studied as means of creating large effective index tunability, motivated by theoretical predictions of the potential for unity absorption in resonantly excited graphene nanostructures. However, the poor radiative coupling to graphene plasmonic nanoresonators and low graphene carrier mobilities from imperfections in processed graphene samples have led to low modulation depths in experimental attempts at creating tunable absorption in graphene devices. Here we demonstrate electronically tunable perfect absorption in graphene, covering less than 10% of the surface area, by incorporating multiscale nanophotonic structures composed of a low-permittivity substrate and subwavelength noble metal plasmonic antennas to enhance the radiative coupling to deep subwavelength graphene nanoresonators. To design the structures, we devised a graphical method based on effective surface admittance, elucidating the origin of perfect absorption arising from critical coupling between radiation and graphene plasmonic modes. Experimental measurements reveal 96.9% absorption in the graphene plasmonic nanostructure at 1389 cm(-1), with an on/off modulation efficiency of 95.9% in reflection.</P>