Abstract-Strong Coupling of Epsilon-Near-Zero Phonon Polaritons in Polar Dielectric Heterostructures

Nikolai Christian Passler, Christopher R. Gubbin, Thomas Graeme Folland, Ilya Razdolski, D. Scott Katzer, David F. Storm, Martin Wolf, Simone De Liberato, Joshua D. Caldwell, Alexander Paarmann

http://export.arxiv.org/abs/1811.05754

We report the first observation of epsilon near zero (ENZ) phonon polaritons in an ultrathin AlN film fully hybridized with surface phonon polaritons (SPhP) supported by the adjacent SiC substrate. Employing a strong coupling model for the analysis of the dispersion and electric field distribution in these hybridized modes, we show that they share the most prominent features of the two precursor modes. The novel ENZ-SPhP coupled polaritons with a highly propagative character and deeply sub-wavelength light confinement can be utilized as building blocks for future infrared and terahertz (THz) nanophotonic integration and communication devices.

Abstract-Polaritons in layered 2D materials

Tony Low, Andrey Chaves, Joshua D. Caldwell, Anshuman Kumar, Nicholas X. Fang, Phaedon Avouris, Tony F. Heinz, Francisco Guinea, Luis Martin-Moreno, Frank Koppens

(Submitted on 14 Oct 2016 (v1), last revised 7 Jul 2017 (this version, v3))

https://arxiv.org/abs/1610.04548

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride (hBN), low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides (TMDs), reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy (SNOM). Here, we review recent progress in state-of-the-art experiments, survey the vast library of polaritonic modes in 2D materials, their optical spectral properties, figures-of-merit and application space. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials.

Researchers explore new 2D materials that could make devices faster, smaller, and efficient

http://www.nanowerk.com/nanotechnology-news/newsid=45205.php

(Nanowerk News) A new study by an international team of researchers led by the University of Minnesota highlights how manipulation of 2D materials could make our modern day devices faster, smaller, and better.

The findings are now online and will be published in Nature Materials ("Polaritons in layered two-dimensional materials").

Two-dimensional materials allow strong light-matter interactions through polaritons.

Two-dimensional materials are a class of nanomaterials that are only a few atoms in thickness. Electrons in these materials are free to move in the two-dimensional plane, but their restricted motion in the third direction is governed by quantum mechanics. Research on these nanomaterials is still in its infancy, but 2D materials such as graphene, transition metal dichalcogenides and black phosphorus have garnered tremendous attention from scientists and engineers for their amazing properties and potential to improve electronic and photonic devices.

In this study, researchers from the University of Minnesota, MIT, Stanford, U.S. Naval Research Laboratory, IBM, and universities in Brazil, UK and Spain, teamed up to examine the optical properties of several dozens of 2D materials. The goal of the paper is to unify understanding of light-matter interactions in these materials among researchers and explore new possibilities for future research.

They discuss how polaritons, a class of quasiparticles formed through the coupling of photons with electric charge dipoles in solid, allow researchers to marry the speed of photon light particles and the small size of electrons.

“With our devices, we want speed, efficiency, and we want small. Polaritons could offer the answer,” said Tony Low, a University of Minnesota electrical and computer engineering assistant professor and lead author of the study.

By exciting the polaritons in 2D materials, electromagnetic energy can be focused down to a volume a million times smaller compared to when its propagating in free space.

“Layered two-dimensional materials have emerged as a fantastic toolbox for nano-photonics and nano-optoelectronics, providing tailored design and tunability for properties that are not possible to realize with conventional materials,” said Frank Koppens, group leader at the Institute of Photonic Sciences at Barcelona, Spain, and co-author of the study.

 “This will offer tremendous opportunities for applications.”Others on the team from private industry also recognize the potential in practical applications.“

The study of the plasmon-polaritons in two-dimensions is not only a fascinating research subject, but also offers possibilities for important technological applications,” said Phaedon Avoruris, IBM Fellow at the IBM T. J. Watson Research Center and co-author of the study. “For example, an atomic layer material like graphene extends the field of plasmonics to the infrared and terahertz regions of the electromagnetic spectrum allowing unique applications ranging from sensing and fingerprinting minute amounts of biomolecules, to applications in optical communications, energy harvesting and security imaging.

”The new study also examined the possibilities of combining 2D materials. Researchers point out that every 2D material has advantages and disadvantages. Combining these materials create new materials that may have the best qualities of both.

“Every time we look at a new material, we find something new,” Low said. “Graphene is often considered a ‘wonder’ material, but combining it with another material may make it even better for a wide variety of applications.”

In addition to Low, Avoruris and Koppens, other researchers involved in the study include Andrey Chaves, Universidade Federal do Cearán (Brazil) and Columbia University; Joshua D. Caldwell, U.S. Naval Research Laboratory; Anshuman Kumar, University of Minnesota and Massachusetts Institute of Technology; Nicholas X.Fang, MIT; Tony Heinz, Stanford University; Francisco Guinea, IMDEA Nanociencia and University of Manchester; and Luis Martin-Moreno, University of Zaragoza (Spain).

Abstract-Atomic-scale photonic hybrids for mid-infrared and terahertz nanophotonics

• Joshua D. Caldwell,
• Igor Vurgaftman,
• Joseph G. Tischler,
• Orest J. Glembocki,
• Jeffrey C. Owrutsky
• & Thomas L. Reinecke
• 
  • a,b, Illustration of XHs using van der Waals (a) and covalently (b) bonded materials. Phonon polariton layers are highlighted by the ions of a polar crystal attached by 'springs' (bonds).

http://www.nature.com/nnano/journal/v11/n1/fig_tab/nnano.2015.305_F5.html

The field of nanophotonics focuses on the ability to confine light to nanoscale dimensions, typically much smaller than the wavelength of light. The goal is to develop light-based technologies that are impossible with traditional optics. Subdiffractional confinement can be achieved using either surface plasmon polaritons (SPPs) or surface phonon polaritons (SPhPs). SPPs can provide a gate-tunable, broad-bandwidth response, but suffer from high optical losses; whereas SPhPs offer a relatively low-loss, crystal-dependent optical response, but only over a narrow spectral range, with limited opportunities for active tunability. Here, motivated by the recent results from monolayer graphene and multilayer hexagonal boron nitride heterostructures, we discuss the potential of electromagnetic hybrids — materials incorporating mixtures of SPPs and SPhPs — for overcoming the limitations of the individual polaritons. Furthermore, we also propose a new type of atomic-scale hybrid the crystalline hybrid — where mixtures of two or more atomic-scale (~3 nm or less) polar dielectric materials lead to the creation of a new material resulting from hybridized optic phonon behaviour of the constituents, potentially allowing direct control over the dielectric function. These atomic-scale hybrids expand the toolkit of materials for mid-infrared to terahertz nanophotonics and could enable the creation of novel actively tunable, yet low-loss optics at the nanoscale.