Strong interaction between graphene and localized hot spots in all-dielectric metasurfaces

Abstract

The active photonics based on the two-dimensional material graphene has attracted enormous interests for developing the tunable and compact optical devices with high efficiency. Here we integrate graphene into the Fano-resonant all-dielectric metasurfaces consisting of silicon split resonators, and systematically investigate the strong interaction between graphene and the highly localized hot inside feed gaps in the near infrared regime. The numerical results show that the integrated graphene can substantially reduce the Fano resonance due to the coupling effect between the intrinsic absorption of graphene with enhanced electric field in the localized hotspot. With the manipulation of the surface conductivity via varying Fermi level and the layer number of graphene, the Fano resonance strength obtains a significant modulation and is even switched off. This works provides a great degree of freedom to tailor light-matter interaction at the nanoscale and opens up the avenues for actively tunable and integrated nanophotonic device applications, such as the optical biosensing, slow light and enhanced nonlinear effects.

Switchable Electromagnetically Induced Transparency with Toroidal Mode in a Graphene-Loaded All-Dielectric Metasurface

“…The modulation depth is defined as the absolute value of the transmission difference . As shown in Figure 7 b, it is up to 88% at the EIT resonance, which is improved to an appreciable extent on the basis of those reported [ 21 , 22 , 23 , 39 ]; meanwhile the Δ T in the full wavelength range, except the resonance position, is approaching zero. In addition, the on/off ratio (the transmission ratio between E F = 0.7 eV and 0 eV) reaches up to 12.2 at the EIT resonance, as presented in the inset of Figure 7 b.…”

“…Its conductivity can be dynamically modulated by changing the Fermi level through electrostatic gating or chemical doping [ 20 ]. Hybrid graphene–dielectric metasurfaces exhibit excellent modulation performance based on Fano resonance [ 21 , 22 , 23 ]. Nevertheless, they are not suitable for optical switching.…”

Tunable Bound States in the Continuum in All-Dielectric Terahertz Metasurfaces

“…Nevertheless, for dielectric metasurfaces, they are concentrated within the dielectric, which limits the light interaction with the surrounding medium [19]. Therefore, the split gaps are introduced in dielectric bars of the unit cell to improve the localized electromagnetic fields and the light interaction with the surrounding medium, due to the slot waveguide effect [45]. At first, the transmission spectrum of the proposed structure is investigated, with the length difference ∆L = 20 µm, the Fermi level of graphene monolayer set as 0 eV, and the temperature of the STO film set as 300 K. In Figure 2a, one can observe a sharp resonance dip at 0.6223 THz and the transmission profile with a characteristic of dip/peak pair has a distinct asymmetric Fano lineshape [20].…”

Active control of electromagnetically induced transparency analog in all-dielectric metamaterials loaded with graphene

“…So far, considerable effort has been devoted to graphene metamaterials [24][25][26][27][28][29][30] or hybrid metal-graphene metamaterials for controllable EIT resonance [31][32][33][34][35][36][37][38]. Most recently, some pioneering works have paid attention to the coupling effect between graphene and the low-loss 'trapped mode' in all-dielectric metamaterials [39][40][41][42][43][44]. However, the interaction between graphene and the classical EIT resonance in all-dielectric metamaterials in the near infrared has yet to be explored.…”