Abstract
Exerting well-defined control over the reflection (R), absorption (A), and transmission (T) of electromagnetic waves is a key objective in quantum optics. To this end, one often utilizes hybrid structures comprised of elements with different optical properties in order to achieve features such as high R or high A for incident light. A desirable goal would be the possibility to tune between all three regimes of nearly perfect reflection, absorption, and transmission within the same device, thus swapping between the cases R → 1, A → 1, and T → 1 dynamically. We here show that a dielectric interfaced with a graphene layer on each side allows for precisely this: by tuning only the Fermi level of graphene, all three regimes can be reached in the THz regime and below. Moreover, we show that the inclusion of cylindrical defects in the system offers a different type of control of the scattering of electromagnetic waves by means of the graphene layers.
Highlights
Our work aims at delivering a progression toward this ambitious and important goal by combining graphene with a dielectric metamaterial. By considering such a material flanked by graphene layers on each surface, we show that one can operate the device in the THz regime and lower in three distinct regimes of high-reflectance, high-transmittance, and high-absorptance by tuning the Fermi levels in graphene
Other works have shown high-absorption of normal incidence light by using e.g. three graphene layers separated by a dielectric spacer and an ENZ metamaterial[45], such a structure is considerably more complex than the one proposed in this work
A recent work reported a technique for producing an effective low-loss dielectric media for THz waves by combining elasrtoiaml eprriocppeorlytideismweethreylsoiflooxradneerwεirth d2opaanndtsaAllo2sOs3taanndgepnotlyoteftorarfdluerortoanethδyl en5e43×
Summary
When a metamaterial with extremely small values for its permittivity or permeability is sandwiched between two graphene sheets, it follows that one can use the corresponding graphene conductivities qi to tune between strong reflection, transmission, or absorption. EFi is the Fermi energy of a given graphene sheet (i = 1, 2), ω is the frequency of the EM wave, τ is the temperature, and trel is the relaxation time (assumed to be the same for both graphene layers). The first path (green curve) begins with the system in a highly reflective state as both graphene layers are gate tuned to equal levels of 800 meV. As the Fermi level in each graphene sheet is reduced by equal amounts, the structure permits substantial transmission of the incident beam. Demonstrating from the conservation equation, the vanishing of the real part of ∂Sx/∂x
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