Metamaterial and plasmonic devices Metamaterials have exciting electromagnetic properties with the potential of revolutionizing various fields of technology. Along the past few years, we have proposed and put forward several concepts to realize electromagnetic devices that can overcome various limitations of conventional components, for radio-waves, THz, optical frequencies, as well as acoustic and matter waves. At radio-frequencies, we have proposed several concepts to improve radiation from electrically small antennas and waveguiding properties in electrically small waveguides. Our main recent efforts have been focused on THz and optical metamaterials, for which we have proposed several concepts for integrated devices and nanostructures based on metamaterials and plasmonics. We have focused a portion of our recent efforts on the modeling and use of planarized metasurfaces and their combinations in order to realize metamaterial effects in conformal geometries, realizable with conventional lithographic techniques. We have worked on the modeling and homogenization of metasurfaces, contributed to their realization and experimental verification and proposed their use to manipulate the polarization of light at the nanoscale. One of our recent contributions has been the introduction of the concept and experimental realization of twisted optical metamaterials, obtained by stacking strongly coupled planar metasurfaces with a rotational twist along the stack axis. With this concept, we were able to prove strong, broadband chirality effects that allowed us to realize ultrathin, broadband circular polarizers operating at visible frequencies. This concept may have even broader reach than just realizing integrated optical devices: by breaking the periodicity of optical metamaterials, we were able to prove that we can introduce more richness in the metamaterial response, and reduce the complexity of the inclusion shape. Plasmonic particles and metamaterials have been proposed in a variety of geometries to concentrate energy in small volumes for energy harvesting and sensing. Usual resonant concentration of energy, however, is limited both spatially and in terms of bandwidth. As another exciting thrust of our theoretical and experimental efforts, we have worked extensively on ideas to overcome these limitations. Using the ‘supercoupling’ idea, we were able to prove that it is possible to increase the spatial extent of field concentration and tunneling by ‘freezing’ the energy once tunneled through small channels with effective zero permittivity (ENZ), thanks to the extremely long effective wavelength. After contributing to the experimental proof of concept at radio-frequencies, we have shown that this concept may be used as an elegant tool to design impedance matched small antennas and frequency-hopping antennas. We have then extended this concept to optical frequencies, realizing ENZ nanolaunchers to significantly boost optical emission and nonlinearities. We also put forward the dual concept of supercoupling: exploiting the plasmonic Brewster angle concept, we showed that it is possible to design ultranarrow plasmonic gratings that possess an angle of total transmission, independent of frequency, allowing to squeeze the impinging energy over very broad frequency ranges. Recently we have also contributed to the experimental realization of this concept, and we were able to conceptually extend this idea to realize ultrabroadband absorbers and directive emitters. In this area, we have been active in related metamaterial geometries for energy squeezing and funneling using plasmonic gratings and metamaterials, and we have worked on optimized grating geometries for solar energy concentration and absorption. The dual phenomenon of emission, particularly relevant for energy-related applications, may be boosted and tailored with metamaterial concepts, as we have recently explored. Energy applications of metamaterials and plasmonics represent an important thrust of our recent and future research interests. To learn more: P. Y. Chen, and A. Alù, “Terahertz Metamaterial Devices Based on Graphene Nanostructures,” Nanotechnology, Vol. 24, No. 45, 455202 (7 pages), October 15, 2013. (web) C. Argyropoulos, F. Monticone, G. D’Aguanno, and A. Alù, “Plasmonic Nanoparticles and Metasurfaces to Realize Fano Spectra at Ultraviolet Wavelengths,” Applied Physics Letters, Vol. 103, No. 14, 143113 (4 pages), October 1, 2013. (web) D. L. Sounas, C. Caloz, and A. Alù, “Giant Non-Reciprocity at the Subwavelength Scale Using Angular Momentum-Biased Metamaterials,” Nature Communications, Vol. 4, No. 2407 (7 pages), September 2, 2013. (web) R. Fleury, and A. Alù, “Extraordinary Sound Transmission through Density-Near-Zero Ultranarrow Channels,” Physical Review Letters, Vol. 111, No. 5, 055501 (5 pages), July 29, 2013. (web, arxiv) F. Monticone, N. Mohammadi Estakhri, and A. Alù, “Full Control of Nanoscale Optical Transmission with a Composite Metascreen,” Physical Review Letters, Vol. 110, No. 20, 203903 (5 pages), May 14, 2013. (web, arxiv) [This paper has been selected as PRL Editor's suggestion; Covered on Phys.org] R. Fleury, and A. Alù, “Enhanced Superradiance in Epsilon-Near-Zero Plasmonic Channels,” Physical Review B, Rapid Communications, Vol. 87, No. 20, 201101(R) (5 pages), May 10, 2013. (web, arxiv) C. Argyropoulos, K. Q. Le, N. Mattiucci, G. D’Aguanno, and A. Alù, “Broadband Absorbers and Selective Emitters Based on Plasmonic Brewster Metasurfaces,” Physical Review B, Vol. 87, No. 20, 205112 (6 pages), May 10, 2013. (web, arxiv) A. Alù, "Wave-Shaping Surfaces,” Physics, Vol. 6, No. 53, May 6, 2013, (invited paper). (web) G. Castaldi, S. Savoia, V. Galdi, A. Alù, and N. Engheta, “PT Metamaterials via Complex-Coordinate Transformation Optics,” Physical Review Letters, Vol. 110, No. 17, 173901 (5 pages), April 24, 2013. (web, arxiv) [This paper has been selected as PRL Editor's suggestion] P. Y. Chen, C. Argyropoulos, and A. Alù, “Terahertz Antenna Phase Shifters Using Integrally-Gated Graphene Transmission-Lines,” IEEE Transactions on Antennas and Propagation, Special Issue on Antennasa and Propagation at Mm- and Sub Mm-Waves, Vol. 61, No. 4, Part 1, pp. 1528-1537, April 1, 2013.. (web) F. Monticone, C. Argyropoulos, and A. Alù, “Multi-Layered Plasmonic Covers for Comblike Scattering Response and Optical Tagging,” Physical Review Letters, Vol. 110, No. 11, 113901 (5 pages), March 12, 2013. (arxiv) [This paper has been selected as PRL Editor's suggestion] Y. Zhao, and A. Alù, “Tailoring the Dispersion of Plasmonic Nanorods to Realize Broadband Optical Meta-Waveplates,” Nano Letters, Vol. 13, No. 3, pp. 1086-1091, February 5, 2013. (web) F. Shafiei*, F. Monticone*, K. Q. Le, X. X. Liu, T. Hartsfield, A. Alù, and X. Li, “A Subwavelength Plasmonic Metamolecule Exhibiting Magnetic-Based Optical Fano Resonance,” Nature Nanotechnology, Vol. 8, pp. 95-99, January 27, 2013.. (web) [A News and Views highlighting our findings has also appeared in the same issue] J. Soric, S. Maci, N. Engheta, and A. Alù, “Omnidirectional Small Antennas Based on ε-Near-Zero Channel Matching,” IEEE Transactions on Antennas and Propagation, Vol. 61, No. 1, pp. 33-44, January 2013. (web) C. Argyropoulos, P. Y. Chen, F. Monticone, G. D’Aguanno, and A. Alù, “Nonlinear Plasmonic Cloaks to Realize Giant All-Optical Scattering Switching,” Physical Review Letters, Vol. 108, No. 26, 263905 (5 pages), June 27, 2012. (web) Y. Zhao, M. A. Belkin, and A. Alù, “Twisted Optical Metamaterials for Planarized, Ultrathin, Broadband Circular Polarizers,” Nature Communications, Vol. 3, No. 870 (7 pages), May 29, 2012. (web) C. Argyropoulos, G. D’Aguanno, N. Mattiucci, M. J. Bloemer, and A. Alù, “Matching and Funneling Light at the Plasmonic Brewster Angle," Physical Review B, Vol. 85, No. 2, 024304 (9 pages), January 31, 2012. (web) C. Argyropoulos, P. Y. Chen, G. D’Aguanno, N. Engheta, and A. Alù, “Boosting Optical Nonlinearities in Epsilon-Near-Zero Plasmonic Channels,” Physical Review B, Vol. 85, No. 4, 045129 (5 pages), January 27, 2012. (web) P. Y. Chen, and A. Alù, “Subwavelength Imaging Using Phase-Conjugating Nonlinear Nanoantenna Arrays,” Nano Letters, Vol. 11, No. 12, pp 5514–5518, November 16, 2011. (web) Y. Zhao, and A. Alù, “Manipulating Light Polarization with Ultrathin Plasmonic Metasurfaces,” Physical Review B, Vol. 84, No. 20, 205428 (6 pages), November 16, 2011. (web) P. Y. Chen, and A. Alù, “Mantle Cloaking Using Thin Patterned Metasurfaces,” Physical Review B, Vol. 84, No. 20, 205110 (13 pages), November 10, 2011. (web) P. Y. Chen, and A. Alù, “Atomically Thin Surface Cloak Using Graphene Monolayers,” ACS Nano, Vol. 5, No. 7, pp. 5855-5863, July 26, 2011. [spotlight in Nanowerk.com] (web) X X. Liu, and A. Alù, “Limitations and Potentials of Metamaterial Lenses,” Journal of Nanophotonics, Vol. 5, 053509 (13 pages), June 20, 2011, (invited paper). (web) A. Alù, G. D’Aguanno, N. Mattiucci, and M. J. loemer, “Plasmonic Brewster Angle: Broadband Extraordinary Transmission through Optical Gratings,” Physical Review Letters, Vol. 106, No. 12, 123902 (4 pages), March 23, 2011. (web)