Showing papers by "Nuno M. R. Peres published in 2018"

Probing the ultimate plasmon confinement limits with a van der Waals heterostructure

Abstract: The ability to confine light into tiny spatial dimensions is important for applications such as microscopy, sensing, and nanoscale lasers. Although plasmons offer an appealing avenue to confine light, Landau damping in metals imposes a trade-off between optical field confinement and losses. We show that a graphene-insulator-metal heterostructure can overcome that trade-off, and demonstrate plasmon confinement down to the ultimate limit of the length scale of one atom. This is achieved through far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric spacer between graphene and metal rods. A theoretical model that takes into account the nonlocal optical response of both graphene and metal is used to describe the results. These ultraconfined plasmonic modes, addressed with far-field light excitation, enable a route to new regimes of ultrastrong light-matter interactions.

Probing nonlocal effects in metals with graphene plasmons

Abstract: The authors thank Sebastien Nanot and Itai Epstein for valuable discussions and comments. E.J.C.D., Yu.V.B. and N.M.R.P. acknowledge support from the European Commission through the project GrapheneDriven Revolutions in ICT and Beyond (Ref. No. 785219), and from the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013. E.J.C.D. acknowledges FCT for the grant CFUM-BI-14/2016. D.A.I. acknowledges the FPI grant BES-2014-068504. F.H.L.K. acknowledges financial support from the Government of Catalonia trough the SGR grant (2014-SGR-1535), and from the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0522), support by Fundacio Cellex Barcelona, CERCA Programme / Generalitat de Catalunya and the Mineco grants Ramn y Cajal (RYC-2012-12281) and Plan Nacional (FIS201347161-P and FIS2014-59639-JIN). Furthermore, the research leading to these results has received funding from the European Union Seventh Framework Programme under grant agreement no.696656 Graphene Flagship, the ERC starting grant (307806, CarbonLight), and project GRASP (FP7-ICT-2013-613024-GRASP). N. A. M. is a VILLUM Investigator supported by VILLUM FONDEN (grant No. 16498). Center for Nano Optics is financially supported by the University of Southern Denmark (SDU 2020 funding). Center for Nanostructured Graphene is supported by the Danish National Research Foundation (DNRF103).

Nonlinear optical responses of crystalline systems: Results from a velocity gauge analysis

Abstract: The work of G.B.V. and D.J.P. is supported by Fundacao para a Ciencia e Tecnologia (FCT) under the grants PD/BI/129220/2017 and PD/BD/135019/2017 respectively. N.M.R.P. acknowledges funding from the European Commission within the project Graphene-Driven Revolutions in ICT and Beyond (ref. 696656) and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013.

Scattering of graphene plasmons at abrupt interfaces: an analytic and numeric study

Abstract: A.J.C. acknowledges the scholarship from the Brazilian agency CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico). B.A., Y.V.B., and N.M.R.P. acknowledge support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. No. 696656). P.A.D.G. acknowledges financial support from the VILLUM Fonden (Grant No. 16498), and from the Center for Nanostructured Graphene sponsored by the Danish National Research Foundation (project DNRF103). N.M.R.P. also acknowledges the hospitality of the MackGraphe Center, at Mackenzie Presbyterian University, where this work has started, the projects Fapesp 2012/50259-8 and 2016/11814-7, and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013.

Magnetic-field-assisted transmission of THz waves through a graphene layer combined with a periodically perforated metallic film

Abstract: We consider a graphene sheet encapsulated in a two-dimensional (2D) metallic grating and a substrate (${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$) and subjected to an external magnetic field (in Faraday configuration). The grating consists of a thin perfectly conducting metal film perforated with a 2D periodic array of square holes. According to our calculations, significant changes in the spectra of the Faraday rotation angle of the transmitted wave and of the magnetic circular dichroism should be expected in this situation compared to bare graphene. We explain this enhancement by the excitation of graphene magnetoplasmons that accompanies the transmission of the electromagnetic wave through the structure. The results can be interesting for applications in THz photonics, such as switchable rotating polarizer and optical isolator.

Probing the Ultimate Plasmon Confinement Limits with a Van der Waals heterostructure

Abstract: The ability to confine light into tiny spatial dimensions is important for applications such as microscopy, sensing and nanoscale lasers. While plasmons offer an appealing avenue to confine light, Landau damping in metals imposes a trade-off between optical field confinement and losses. We show that a graphene-insulator-metal heterostructure can overcome that trade-off, and demonstrate plasmon confinement down to the ultimate limit of the lengthscale of one atom. This is achieved by far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric h-BN spacer between graphene and metal rods. A theoretical model which takes into account the non-local optical response of both graphene and metal is used to describe the results. These ultra-confined plasmonic modes, addressed with far-field light excitation, enables a route to new regimes of ultra-strong light-matter interactions.

Channel surface plasmons in a continuous and flat graphene sheet

Abstract: A.J.C. acknowledges a scholarship from the Brazilian agency CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico). N.M.R.P. acknowledges the European Commission through the project Graphene-Driven Revolutions in ICT and Beyond (Ref. No. 696656) and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013. D.R.C. and G.A.F. acknowledge CNPq under the PRONEX/FUNCAP grants and the CAPES Foundation.

Propagation of surface plasmons on plasmonic Bragg gratings

Abstract: We use coupled-mode theory to describe the scattering of a surface-plasmon polariton (SPP) from a square wave grating (Bragg grating) of finite extension written on the surface of either a metal-dielectric interface or a dielectric-dielectric interface covered with a patterned graphene sheet. We find analytical solutions for the reflectance and transmittance of SPP's when only two modes (forward- and back-scattered) are considered. We show that in both cases the reflectance spectrum presents stop-bands where the SPP is completely back-scattered, if the grating is not too shallow. In addition, the reflectance coefficient shows Fabry-Perot oscillations when the frequency of the SPP is out of the stop-band region. For a single dielectric well, we show that there are frequencies of transmission equal to 1. We also provide simple analytical expression for the different quantities in the electrostatic limit.