Publications by Type: Journal Article

2018
Sharmila N. Shirodkar, Marios Mattheakis, Paul Cazeaux, Prineha Narang, Marin Soljačić, and Efthimios Kaxiras. 5/2018. “Quantum plasmons with optical-range frequencies in doped few-layer graphene.” Phys. Rev. B, 97, Pp. 195435. Publisher's VersionAbstract
Although plasmon modes exist in doped graphene, the limited range of doping achieved by gating restricts the plasmon frequencies to a range that does not include the visible and infrared. Here we show, through the use of first-principles calculations, that the high levels of doping achieved by lithium intercalation in bilayer and trilayer graphene shift the plasmon frequencies into the visible range. To obtain physically meaningful results, we introduce a correction of the effect of plasmon interaction across the vacuum separating periodic images of the doped graphene layers, consisting of transparent boundary conditions in the direction perpendicular to the layers; this represents a significant improvement over the exact Coulomb cutoff technique employed in earlier works. The resulting plasmon modes are due to local field effects and the nonlocal response of the material to external electromagnetic fields, requiring a fully quantum mechanical treatment. We describe the features of these quantum plasmons, including the dispersion relation, losses, and field localization. Our findings point to a strategy for fine-tuning the plasmon frequencies in graphene and other two-dimensional materials.
visiblegrapheneplasmons_1703.01558.pdf
Matthias Maier, Marios Mattheakis, Efthimios Kaxiras, Mitchell Luskin, and Dionisios Margetis. 1/2018. “Universal behavior of dispersive Dirac cone in gradient-index plasmonic metamaterials.” Phys. Rev. B, 97, 3, Pp. 035307. Publisher's VersionAbstract
We demonstrate analytically and numerically that the dispersive Dirac cone emulating an epsilon-near-zero (ENZ) behavior is a universal property within a family of plasmonic crystals consisting of two-dimensional (2D) metals. Our starting point is a periodic array of 2D metallic sheets embedded in an inhomogeneous and anisotropic dielectric host that allows for propagation of transverse-magnetic (TM) polarized waves. By invoking a systematic bifurcation argument for arbitrary dielectric profiles in one spatial dimension, we show how TM Bloch waves experience an effective dielectric function that averages out microscopic details of the host medium. The corresponding effective dispersion relation reduces to a Dirac cone when the conductivity of the metallic sheet and the period of the array satisfy a critical condition for ENZ behavior. Our analytical findings are in excellent agreement with numerical simulations.
universalenz2018.pdf
2017
Constantinos A. Valagiannopoulos, Marios Mattheakis, Sharmila N. Shirodkar, and Efthimios Kaxiras. 2017. “Manipulating polarized light with a planar slab of Black Phosphorus.” Journal of Physics Communications, 1, Pp. 045003. Publisher's VersionAbstract

Wave polarization contains valuable information for electromagnetic signal processing; hence, the ability to manipulate it can be extremely useful in photonic devices. In this work, we propose designs solely comprised of one of the emerging and interesting two-dimensional media; Black Phosphorus. Due to substantial in-plane anisotropy, the simplest possible structure: a single slab of Black Phosphorus, can be very efficient and for manipulating the polarization state of electromagnetic waves. We propose Black Phosphorus films that filter the fields along one direction, or achieve large magnetic-free Faraday rotation, or convert linear polarization to circular; these slabs can be employed as  components in numerous mid-IR integrated devices.

bp_jpc2017.pdf
2016
M.Mattheakis, C. A. Valagiannopoulos, and E. Kaxiras. 11/10/2016. “Epsilon-Near-Zero behavior from Plasmonic Dirac Point: theory and realization using two-dimensional materials.” Physical Review B, 94, 20, Pp. 201404(R). Publisher's VersionAbstract

The electromagnetic response of a two-dimensional metal embedded in a periodic array of a dielectric host can give rise to a plasmonic Dirac point that emulates Epsilon-Near-Zero (ENZ) behavior. This theoretical result is extremely sensitive to structural features like periodicity of the dielectric medium and thickness imperfections. We propose that such a device can actually be realized by using graphene as the 2D metal and materials like the layered semiconducting transition-metal dichalcogenides or hexagonal boron nitride as the dielectric host. We propose a systematic approach, in terms of design characteristics, for constructing metamaterials with linear, elliptical and hyperbolic dispersion relations which produce ENZ behavior, normal or negative diffraction.

arXiv_PDP_ENZ.pdf
M Mattheakis, I. J. Pitsios, G. P. Tsironis, and S. Tzortzakis. 2016. “Extreme events in complex linear and nonlinear photonic media.” Chaos, Solitons & Fractals, 84, Pp. 73-80. Publisher's VersionAbstract

Ocean rogue waves (RW) are huge solitary waves that have for long triggered the interest of scientists. The RWs emerge in a complex environment and it is still under investigation if they are due to linear or nonlinear processes. Recent works have demonstrated that RWs appear in various other physical systems such as microwaves, nonlinear crystals, cold atoms, etc. In this work we investigate optical wave propagation in strongly scattering random lattices embedded in the bulk of transparent glasses. In the linear regime we observe the appearance of extreme waves, RW-type, that depend solely on the scattering properties of the medium. Interestingly, the addition of nonlinearity does not modify the RW statistics, while as the nonlinearities are increased multiple-filamentation and intensity clamping destroy the RW statistics. Numerical simulations agree nicely with the experimental findings and altogether prove that optical rogue waves are generated through the linear strong scattering in such complex environments.

arXiv_ExtremeEvents.pdf
M.Mattheakis, T. Oikonomou, Μ Molina, and G. P. Tsironis. 2016. “Phase transition in PT symmetric active plasmonic systems.” IEEE Journal of Selected Topics in Quantum Electronics, 22, 5, Pp. 1-7. Publisher's VersionAbstract

Surface plasmon polaritons (SPPs) are coherent electromagnetic surface waves trapped on an insulator-conductor interface. The SPPs decay exponentially along the propagation due to conductor losses, restricting the SPPs propagation length to few microns. Gain materials can be used to counterbalance the aforementioned losses. We provide an exact expression for the gain, in terms of the optical properties of the interface, for which the losses are eliminated. In addition, we show that systems characterized by lossless SPP propagation are related to PT symmetric systems. Furthermore, we derive an analytical critical value of the gain describing a phase transition between lossless and prohibited SPPs propagation. The regime of the aforementioned propagation can be directed by the optical properties of the system under scrutiny. Finally, we perform COMSOL simulations verifying the theoretical findings.

arXiv_PTplasmons.pdf
2014
F Perakis, M Mattheakis, and G. P. Tsironis. 2014. “Small-world networks of optical fiber lattices.” Journal of Optics, 16, Pp. 102003. Publisher's VersionAbstract

We use a simple dynamical model and explore coherent dynamics of wavepackets in complex networks of optical fibers. We start from a symmetric lattice and through the application of a Monte–Carlo criterion we introduce structural disorder and deform the lattice into a small-world network regime. We investigate in the latter both structural (correlation length) as well as dynamical (diffusion exponent) properties and find that both exhibit a rapid crossover from the ordered to the fully random regime. For a critical value of the structural disorder parameter ρ≈0.25 transport changes from ballistic to sub-diffusive due to the creation strongly connected local clusters and channels of preferential transport in the small world regime.

arXiv_SmallWorldNetworks.pdf
2012
MM Mattheakis, G. P. Tsironis, and VI Kovanis. 2012. “Luneburg lens waveguide networks.” Journal of Optics, 14, Pp. 114006. Publisher's VersionAbstract

We investigate certain configurations of Luneburg lenses that form light propagating and guiding networks. We study single Luneburg lens dynamics and apply the single lens ray tracing solution to various arrangements of multiple lenses. The wave propagating features of the Luneburg lens networks are also verified through direct numerical solutions of Maxwell’s equations. We find that Luneburg lenses may form efficient waveguides for light propagation and guiding. The additional presence of nonlinearity improves the focusing characteristics of the networks.

arXiv_LLwaveguides.pdf

Pages