arXiv subjects

Andrei Nemilentsau

Publications and source records attributed to Andrei Nemilentsau.

15 recordsLinked to original sources

arXiv2019

Resonance Energy Transfer and Quantum Entanglement Mediated by Epsilon-Near-Zero and Other Plasmonic Waveguide Systems

The entanglement and resonance energy transfer between two-level quantum emitters are typically limited to sub-wavelength distances due to the inherently short-range nature of the dipole-dipole interactions. Moreover, the entanglement of quantum systems is hard to preserve for a long time period due to decoherence and dephasing mainly caused by radiative and nonradiative losses. In this work, we outperform the aforementioned limitations by presenting efficient long-range inter-emitter entanglement and large enhancement of resonance energy transfer between two optical qubits mediated by epsilon-near-zero (ENZ) and other plasmonic waveguide types, such as V-shaped grooves and cylindrical nanorods. More importantly, we explicitly demonstrate that the ENZ waveguide resonant energy transfer and entanglement performance drastically outperforms the other waveguide systems. Only the excited ENZ mode has an infinite phase velocity combined with a strong and homogeneous electric field distribution, which leads to a giant energy transfer and efficient entanglement independent to the emitters separation distances and nanoscale positions in the ENZ nanowaveguide, an advantageous feature that can potentially accommodate multi-qubit entanglement. Moreover, the transient entanglement can be further improved and become almost independent of the detrimental decoherence effect when an optically active (gain) medium is embedded inside the ENZ waveguide. We also present that efficient steady-state entanglement can be achieved by using a coherent external pumping scheme. Finally, we report a practical way to detect the steady-state entanglement by computing the second-order correlation function. The presented findings stress the importance of plasmonic ENZ waveguides in the design of the envisioned on-chip quantum communication and information processing plasmonic nanodevices.

physics.optics↗

arXiv2019

Switchable and unidirectional plasmonic beacons in hyperbolic 2D materials

In hyperbolic 2D materials, energy is channeled to their deep subwavelength polaritonic modes via four narrow beams. Here we consider the launching of surface polaritons in the hyperbolic 2D materials and demonstrate that efficient uni-directional excitation is possible with an elliptically polarized electric dipole, with the optimal choice of dipole ellipticity depending on the materials optical constants. The selection rules afforded by the choice of dipole polarization allow turning off up to two beams, and even three if the dipole is placed close to an edge. This makes the dipole a directionally switchable beacon for the launching of sub-difractional polaritonic beams, a potential logical gate. We develop an analytical approximation of the excitation process which describes the results of the numerical simulations well and affords a simple physical interpretation.

cond-mat.mes-hall↗

arXiv2018

Tuning 2D hyperbolic plasmons in black phosphorus

Black phosphorus presents a very anisotropic crystal structure, making it a potential candidate for hyperbolic plasmonics, characterized by a permittivity tensor where one of the principal components is metallic and the other dielectric. Here we demonstrate that atomically thin black phosphorus can be engineered to be a hyperbolic material operating in a broad range of the electromagnetic spectrum from the entire visible spectrum to ultraviolet. With the introduction of an optical gain, a new hyperbolic region emerges in the infrared. The character of this hyperbolic plasmon depends on the interplay between gain and loss along the two crystalline directions.

cond-mat.mtrl-sci↗

arXiv2017

Tunable Graphene Metasurface Reflectarray for Cloaking, Illusion and Focusing

We present a graphene-based metasurface that can be actively tuned between different regimes of operation, such as anomalous beam steering and focusing, cloaking and illusion optics, by applying electrostatic gating without modifying the geometry of the metasurface. The metasurface is designed by placing graphene nano-ribbons (GNRs) on a dielectric cavity resonator, where interplay between geometric plasmon resonances in the ribbons and Fabry-Perot resonances in the cavity is used to achieve 2$π$ phase shift. As a proof of the concept, we demonstrate that wavefront of the field reflected from a triangular bump covered by the metasurface can be tuned by applying electric bias so as to resemble that of bare plane and of a spherical object. Moreover, reflective focusing and change of the reflection direction for the above-mentioned cases are also shown.

physics.optics↗

arXiv2017

Ultracompact amplitude modulator by coupling hyperbolic polaritons over a graphene-covered gap

The hyperbolic phonon-polaritons within the Reststrahlen band of hBN are of great interest for applications in nanophotonics as they are capable of propagating light signals with low losses over large distances. However, due to the phononic nature of the polaritons in hBN, amplitude modulation of its signal proves to be difficult and has been underexplored. In this paper, we propose theoretically a broadband efficient amplitude modulator for hyperbolic rays in hBN operating in the frequency range between 1450 cm$^{-1}$ and 1550 cm$^{-1}$. The modulating region comprises a few tens of nanometers wide gap carved within the hBN slab and covered by a graphene layer, where electrostatically gated graphene serves as a mediator that facilitates the coupling between phonon-polaritons on each side of the gap through plasmonic modes within graphene. We demonstrate that such an ultra compact modulator has insertion losses as low as 3 dB and provides modulation depth varying between 14 and 20 dB within the type-II hyperbolicity region of hBN.

cond-mat.mes-hall↗

arXiv2017

Direct Investigation of the Birefringent Optical Properties of Black Phosphorus with Picosecond Interferometry

Black phosphorus (BP) is an emerging two-dimensional semiconducting material with great potential for nanoelectronic and nanophotonic applications, especially owing to its unique anisotropic electrical and optical properties. Many theoretical studies have predicted the anisotropic optical properties of BP, but the direct experimental quantification remains challenging. The difficulties stem from the ease of BP's degradation when exposed to air in ambient conditions, and from the indirect nature of conventional approaches that are subject to large measurement uncertainties. This work reports a direct investigation of the birefringent optical constants of micrometer-thick BP samples with picosecond (ps) interferometry, over the wavelength range from 780 to 890 nm. In this ps-interferometry approach, an ultrathin (5 nm) platinum layer for launching acoustic waves naturally protects the BP flake from degradation. The birefringent optical constants of BP for light polarization along the two primary crystalline orientations, zigzag and armchair, are directly obtained via fitting the attenuated Brillouin scattering signals. A bi-exponential model is further proposed to analyze the BS signals for a random incident light polarization. The BP experimental results and the associated measurement sensitivity analysis demonstrate the reliability and accuracy of the ps-interferometry approach for capturing the polarization-dependent optical properties of birefringent materials.

physics.optics↗

arXiv2017

Ultrafast Graphene Light Emitter

Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge. Here, we demonstrate electrically driven ultrafast graphene light emitters that achieve light pulse generation with up to 10 GHz bandwidth, across a broad spectral range from the visible to the near-infrared. The fast response results from ultrafast charge carrier dynamics in graphene, and weak electron-acoustic phonon-mediated coupling between the electronic and lattice degrees of freedom. We also find that encapsulating graphene with hexagonal boron nitride (hBN) layers strongly modifies the emission spectrum by changing the local optical density of states, thus providing up to 460 % enhancement compared to the grey-body thermal radiation for a broad peak centered at 720 nm. Furthermore, the hBN encapsulation layers permit stable and bright visible thermal radiation with electronic temperatures up to 2,000 K under ambient conditions, as well as efficient ultrafast electronic cooling via near-field coupling to hybrid polaritonic modes. These high-speed graphene light emitters provide a promising path for on-chip light sources for optical communications and other optoelectronic applications.

cond-mat.mes-hall↗

arXiv2016

Notes on photonic topological insulators and scattering-protected edge states - a brief introduction

The topic of photonic topological insulators and scattering-protected edge states bridges concepts from condensed matter physics and electromagnetics, and necessitates understanding the Berry potential and related concepts. These notes are an attempt at a moderately self-contained introduction to the topic, including two detailed photonic examples drawn from the literature. We made these notes in the process of trying to understand this topic ourselves, and we are posting this material in the spirit of helping other researchers start to understand this material. We claim no novelty in the material or its presentation.

cond-mat.mes-hall↗

arXiv2016

Directive Surface Plasmons on Tunable Two-Dimensional Hyperbolic Metasurfaces and Black Phosphorus: Green's Function and Complex Plane Analysis

We study the electromagnetic response of two- and quasi-two-dimensional hyperbolic materials, on which a simple dipole source can excite a well-confined and tunable surface plasmon polariton (SPP). The analysis is based on the Green's function for an anisotropic two-dimensional surface, which nominally requires the evaluation of a two-dimensional Sommerfeld integral. We show that for the SPP contribution this integral can be evaluated efficiently in a mixed continuous-discrete form as a continuous spectrum contribution (branch cut integral) of a residue term, in distinction to the isotropic case, where the SPP is simply given as a discrete residue term. The regime of strong SPP excitation is discussed, and complex-plane singularities are identified, leading to physical insight into the excited SPP. We also present a stationary phase solution valid for large radial distances. Examples are presented using graphene strips to form a hyperbolic metasurface, and thin-film black phosphorus. The Green's function and complex-plane analysis developed allows for the exploration of hyperbolic plasmons in general 2D materials.

cond-mat.mtrl-sci↗

arXiv2016

Layer Tunable Third-Harmonic Generation in Multilayer Black Phosphorus

Black phosphorus has been the subject of growing interest due to its unique band structure that is both layer dependent and anisotropic. While many have studied the linear optical response of black phosphorus, the nonlinear response has remained relatively unexplored. Here we report on the observation of third-harmonic generation in black phosphorus using an ultrafast near-IR laser and measure Chi(3) experimentally for the first time. It was found that the third-harmonic emission is highly anisotropic, dependent on the incident polarization, and varies strongly with the number of layers present due to signal depletion and phase-matching conditions.

cond-mat.mtrl-sci↗

arXiv2016

Broadband achromatic anomalous mirror in near-IR and visible frequency range

The anomalous achromatic mirror operating in near-IR and visible frequency range was designed using an array of metal-insulator-metal (MIM) resonators. An incident wave interacting with MIM resonator experiences phase shift that is equal to the optical path travelled by the gap plasmon, excited by the wave. The phase gradient along the mirror surface is created through the difference in plasmons optical paths in resonators of different lengths. In the frequency region well below the plasma frequency of the metal, the phase gradient is a linear function of frequency, and thus the mirror operates in achromatic regime, i.e. reflection angle does not depend on the radiation frequency. Using silver-air-silver resonators, we predicted that the mirror can steer normally incident beam to angles as large as 40$^{\circ}$ with high radiation efficiency (exceeding 98 $\%$) and small Joule losses (below 10 $\%$).

cond-mat.mes-hall↗

arXiv2016

The effects of three-dimensional defects on one-way surface plasmon propagation for photonic topological insulators comprised of continuous media

We have investigated the one-way surface plasmon-polariton (SPP) at the interface of a continuous magneto-plasma material and metal. We demonstrated that TM modes inside a continuous material can be assigned non-trivial Chern numbers analogous to those of topological photonic crystals; moreover these Chern numbers can be calculated analytically. This leads to the appearance of topologically protected surface modes propagating at frequencies inside the bandgap of the magneto-plasma. Previous works considered 2D structures; here we consider the effects of 3D defects, and show that, although backward propagation/reflection cannot occur, side scattering does take place and it has significant effect on the propagation of the surface mode. Several different waveguiding geometries are considered for reducing the effects of side-scattering, and we also consider the effects of metal loss.

cond-mat.mes-hall↗

arXiv2016

Anisotropic 2D materials for tunable hyperbolic plasmonics

Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on-the-spot by gate doping, enabling hyperbolic beams reflection, refraction and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.

cond-mat.mes-hall↗

arXiv2015

Chiral plasmon in gapped Dirac systems

We study the electromagnetic response and surface electromagnetic modes in a generic gapped Dirac material under pumping with circularly polarized light. The valley imbalance due to pumping leads to a net Berry curvature, giving rise to a finite transverse conductivity. We discuss the appearance of nonreciprocal chiral edge modes, their hybridization and waveguiding in a nanoribbon geometry, and giant polarization rotation in nanoribbon arrays.

cond-mat.mes-hall↗

arXiv2015

Transient and steady-state entanglement mediated by three-dimensional plasmonic waveguides

Entanglement between two qubits (two level atoms) mediated by surface plasmons in three-dimensional plasmonic waveguides is studied using a quantum master equation formalism. Two types of waveguides, a nanowire and a V-shaped channel cut in a flat metal plane, are considered. The Green functions for the waveguides, which rigorously describes the dissipative qubit environment, are calculated numerically using a direct finite-difference time-domain (FDTD) solution of Maxwell's equations. Finite-length effects are shown to play a crucial role in enhancing entanglement, and resonant-length plasmonic waveguides can provide higher entanglement between qubits than infinite-length waveguides. It is also shown that coupling slots can improve entanglement via stronger qubit-waveguide coupling, for both the infinite- and finite-waveguide cases.

quant-ph↗