arXiv subjects

Tiago A. Morgado

Publications and source records attributed to Tiago A. Morgado.

23 records · Page 2Linked to original sources

arXiv2018

Drift-induced Unidirectional Graphene Plasmons

Nonreciprocal photonic devices enable "one-way" light flows and are essential building blocks of optical systems. Here, we investigate an alternative paradigm to break reciprocity and achieve unidirectional subwavelength light propagation fully compatible with modern all-photonic highly-integrated systems. In agreement with a few recent studies, our theoretical model predicts that a graphene sheet biased with a drift electric current has a strong nonreciprocal tunable response. Strikingly, we find that the propagation of the surface plasmon polaritons can be effectively "one-way" and may be largely immune to the backscattering from defects and obstacles. Furthermore, the drift-current biasing may boost the propagation length of the graphene plasmons by more than 100%. Our findings open new inroads in nonreciprocal photonics and offer a new opportunity to control the flow of light with one-atom thick nonreciprocal devices.

physics.optics↗

arXiv2017

Negative Landau damping in bilayer graphene

We theoretically demonstrate that a system formed by two coupled graphene sheets enables a negative damping regime wherein graphene plasmons are pumped by a DC current. This effect is triggered by electrons drifting through one of the graphene sheets and leads to the spontaneous light emission (spasing) and wave instabilities in the mid-infrared range. It is shown that there is a deep link between the drift-induced instabilities and wave instabilities in moving media, as both result from the hybridization of oscillators with oppositely signed frequencies. With a thickness of few nanometers and wide spectral tunability, the proposed structure may find interesting applications in nanophotonic circuitry as an on-chip light source.

cond-mat.mes-hall↗

arXiv2016

Single-Interface Casimir Torque

It is shown that the quantum fluctuations of the electromagnetic field generally induce a torque at the interface of an anisotropic material with another anisotropic or isotropic material. It is proven that this torque depends on an interface zero-point energy determined by the dispersion of the interface (localized and extended) modes. Our theory demonstrates that the single-interface torque is essential to understand the Casimir physics of material systems with anisotropic elements and determines the equilibrium positions of the system.

cond-mat.mes-hall↗

arXiv2015

Analytical solution for the stopping power of the Cherenkov radiation in a uniaxial nanowire material

We derive closed analytical formulae for the power emitted by moving charged particles in a uniaxial wire medium by means of an eigenfunction expansion. Our analytical expressions demonstrate that in the absence of material dispersion the stopping power of the uniaxial wire medium is proportional to the charges velocity, and that there is no velocity threshold for the Cherenkov emission. It is shown that the eigenfunction expansion formalism can be extended to the case of dispersive lossless media. Furthermore, in presence of material dispersion the optimal charge velocity that maximizes the emitted Cherenkov power may be less than the speed of light in vacuum.

cond-mat.mes-hall↗

arXiv2015

Super collimation of the radiation by a point source in a uniaxial wire medium

We investigate the radiation properties of a short horizontal dipole embedded in a uniaxial wire medium. It is shown that the uniaxial wire medium enables a super-collimation of the dipole radiation such that the radiation pattern has a singularity and the radiated fields are non-diffractive in the broadside direction. We derive a closed analytical formula for the power radiated by the dipole. Our theory demonstrates that as a consequence of the ultrahigh density of photonic states of the nanowire array, the power radiated by the dipole is strongly enhanced as compared to that emitted in the dielectric host material.

cond-mat.mes-hall↗