Assistant Professor, University of Texas at Austin

Here you can find an overview of some of the active lines of research on which we are currently working.
 

Metamaterial and Plasmonic Cloaking

Our seminal proposal for the use of plasmonic materials and/or metamaterials to cloak dielectric and/or conducting objects relies on a scattering cancellation phenomenon, based on the negative local polarizability of a cover made of low electric permittivity materials. This cloaking technique has been proven to be relatively robust to changes in the design parameters, geometry and frequency of operation and it has been recently extended to collections of particles, systems of relatively larger size and multi-frequency operation. Applications for camouflaging, non-invasive probing and sensing may be foreseen, spanning various applications in medicine, biology, defense and telecommunications.

We are currently exploring the application of these concepts to acoustic waves.


A plane wave traveling unperturbed through a system of four cloaked impenetrable particles (from [12])

To learn more:

  1. I. Gallina, G. Castaldi, V. Galdi, A. Alů, and N. Engheta, “Power Scattering and Absorption Mediated by Cloak/Anti-Cloak Interactions: A Transformation-Optics Route towards Invisible Sensors,” under review, since January 2010. (arxiv)
  2. A. Alů, and N. Engheta, “Paradox of Zero Forward-Scattering in Magnetodielectric Nanoparticles in Connection with the Optical Theorem,” under review, since November 2009 (invited paper).
  3. A. Alů, and N. Engheta, “Cloaking a Receiving Antenna or a Sensor with Plasmonic Metamaterials,” under review, since November 2009.
  4. A. Alů, and N. Engheta, “Cloaked NSOM Tip for Non-Invasive Near-Field Imaging,” under review, since September 2009.
  5. S. Tricarico, F. Bilotti, A. Alů, and L. Vegni, “Plasmonic Cloaking for Irregular Objects with Anisotropic Scattering Properties,” Physical Review E, in press.
  6. A. Alů, and N. Engheta, “Metamaterial and Plasmonic Cloaking,” in Handbook of Artificial Materials, F. Capolino, ed., Taylor and Francis - CRC Press, Vol. 2, in press.
  7. A. Alů, “Mantle Cloak: Invisibility Induced by a Surface,” Physical Review B, Vol. 80, No. 24, 245115 (5 pages), December 21, 2009. (web) [Fig. 1 from this manuscript has been selected for the Physical Review B Kaleidoscope]
  8. B. Edwards, A. Alů, M. G. Silveirinha, and N. Engheta, "Experimental Verification of Plasmonic Cloaking at Microwave Frequencies," Physical Review Letters, Vol. 103, No. 15, 153901, October 6, 2009. (web)
  9. A. Alů, and N. Engheta, “Plasmonic Cloaks,” in Metamaterials and Plasmonics: Fundamentals, Modelling and Applications, NATO Science Series Book, S Zouhdi, A. Sihvola, A. Vinogradov, eds., Springer Ed., pp. 37-47, 2009.
  10. A. Alů, and N. Engheta, “Cloaking a Sensor,” Physical Review Letters, Vol. 102, No. 23, 233901, June 8, 2009, also in Virtual Journal of Biological Physics Research, Vol. 17, No. 12, June 15, 2009. (web) [A Science News highlighting our findings has appeared on Science, Vol. 175, No. 10, p. 12, May 9, 2009; A Viewpoint article by Prof. F. Javier Garcia de Abajo highlighting this paper has been published on Physics, Vol. 2, No. 47, June 8, 2009]
  11. G. Castaldi, I. Gallina, V. Galdi, A. Alů, and N. Engheta, “Cloak/anti-cloak interactions,” Optics Express, Vol. 17, No. 5, pp. 3101-3114, February 17, 2009. (web, arxiv)
  12. A. Alů, and N. Engheta, “Theory and Potentials of Multi-Layered Plasmonic Covers for Multi-Frequency Cloaking,” New Journal of Physics, Focus Issue on Cloaking and Transformation Optics, Vol. 10, 115036 (15 pages), November 2008, (invited paper). (upenn, web)
  13. M. G. Silveirinha, A. Alů, and N. Engheta, “Cloaking Mechanism with Antiphase Plasmonic Satellites,” Physical Review B, Vol. 78, No. 20, 205109 (9 pages), November 12, 2008. (upenn, web)
  14. A. Alů, and N. Engheta, “Effects of Size and Frequency Dispersion in Plasmonic Cloaking,” Physical Review E, Rapid Communications, Vol. 78, 045602(R), October 27, 2008. (upenn, web)
  15. A. Alů, and N. Engheta, “Dispersion Characteristics of Metamaterial Cloaking Structures,” Electromagnetics, Special Issue on Metamaterials, Vol. 28, No. 7, pp. 464-475, October 2008, (invited paper). (web)
  16. A. Alů, and N. Engheta, “Plasmonic and Metamaterial Cloaking: Physical Mechanisms and Potentials,” Journal of Optics A: Pure and Applied Optics, Vol. 10, No. 9, 093002 (17 pages), August 19, 2008, (invited review paper). (upenn, web) [This paper has been selected to appear in the  Journal of Optics Highlights for 2008]
  17. M. G. Silveirinha, A. Alů, and N. Engheta, “Infrared and Optical Invisibility Cloak with Plasmonic Implants Based on Scattering Cancellation,” Physical Review B, Vol. 78, 075107 (7 pages), August 11, 2008. (upenn, web)
  18. A. Alů, and N. Engheta, “Robustness in Design and Background Variations in Metamaterial/Plasmonic Cloaking,” Radio Science, Special Issue for the 2007 URSI EMT-Symposium in Ottawa, Vol. 43, RS4S01, May 17, 2008, (invited paper). (upenn, web)
  19. A. Alů, and N. Engheta, “Multifrequency Optical Cloaking with Layered Plasmonic Shells,” Physical Review Letters, Vol. 100, 113901, March 18, 2008. (upenn, web) [A News and Views highlighting our findings has appeared on Nature Photonics]
  20. A. Alů, and N. Engheta, “Cloaking and Transparency for Collections of Particles with Metamaterial and Plasmonic Covers,” Optics Express, Vol. 15, No. 12, pp. 7578-7590, June 5, 2007. (upenn, web) [CST University Publication Award 2008]
  21. A. Alů, and N. Engheta, “Plasmonic Materials in Transparency and Cloaking Problems: Mechanism, Robustness, and Physical Insights,” Optics Express, Vol. 15, No. 6, pp. 3318-3332, March 19, 2007. (upenn, web) [A Research Highlight underlining our findings has appeared on Nature Materials]
  22. M. G. Silveirinha, A. Alů, and N. Engheta, “Parallel Plate Metamaterials for Cloaking Structures,” Physical Review E, Vol. 75, 036603 (16 pages), March 7, 2007. (upenn, web)
  23. A. Alů, and N. Engheta, “Achieving Transparency with Plasmonic and Metamaterial Coatings,” Physical Review E, Vol. 72, 016623 (9 pages), July 26, 2005 (erratum in Physical Review E, Vol. 73, 019906, January 24, 2006). (upenn, web, arxiv) [A Nature News article highlighting our findings has appeared on Nature]

Optical Nanocircuits and Nanoelectronics

We have proposed a paradigm for extending the classical low-frequency circuit concepts to IR and optical frequencies, relying on the interaction among plasmonic and non-plasmonic collections of nanoparticles that may act, respectively, as lumped nanoinductors and nanocapacitors. Due to the lack of conductive materials at these high frequencies, the role of conduction currents flowing in a regular circuit is taken by the displacement current flowing across the nanocircuit elements and the role of conductivity is taken by the local electric permittivity, which has a relatively wide variation in optical materials. Parallel and series combinations of nanoelements, nanofilters, nanoinsulators, nanoconnectors, nanoswitches and nanowires have been envisioned in this context, providing the building blocks to design complex functionalities on an optical nanocircuit board. When applied to infinite periodic stacks of plasmonic and non-plasmonic particles or planar layers these concepts allow envisioning optical nanotransmission lines (with forward and backward-wave propagation) and optical negative-index or backward-wave metamaterials.


Electric displacement current flowing in a relatively simple optical nanocircuit

To learn more:

  1. A. Alů, and N. Engheta, “Comparison of Guiding Properties of Plasmonic Voids and Plasmonic Waveguides,” under review, since November 2009 (invited paper).
  2. A. Alů, P. A. Belov, and N. Engheta, “Guided Propagation along Parallel Chains of Optical Nanoparticles,” under review, since September 2009.
  3. A. Alů, and N. Engheta, “Effect of Small Random Disorders and Imperfections on the Performance of Arrays of Plasmonic Nanoparticles,” New Journal of Physics, Vol. 12, 013015 (12 pages), January 18, 2010. (web)
  4. A. Alů, and N. Engheta, “Envisioning an All-Optical Metamaterial Circuit Board at the Nanoscale,” Physical Review Letters, Vol. 103, No. 14, 143902, September 29, 2009, also in Virtual Journal of Nanoscale Science & Technology, Vol. 20, No. 15, October 12, 2009. (web)
  5. A. Alů, P. A. Belov, and N. Engheta, “Parallel-Chain Optical Nanotransmission Line for Low-Loss Ultra-Confined Light Beam,” Physical Review B, Vol. 80, No. 11, 113101 (4 pages), September 8, 2009, also in Virtual Journal of Nanoscale Science & Technology, Vol. 20, No. 5, September 21, 2009. (web)
  6. A. Alů, and N. Engheta, “Guided Propagation along Quadrupolar Chains of Plasmonic Nanoparticles,” Physical Review B, Vol. 79, No. 23, 235412 (12 pages), June 12, 2009, also in Virtual Journal of Nanoscale Science & Technology, Vol. 19, No. 26, June 29, 2009. (web)
  7. A. Alů, and N. Engheta, “Optical Nanoswitch: an Engineered Plasmonic Nanoparticle with Extreme Parameters and Giant Anisotropy,” New Journal of Physics, Vol. 11, 013026 (14 pages), January 20, 2009, also in Virtual Journal of Nanoscale Science & Technology, Vol. 19, No. 7, February 16, 2009. (web, upenn, arxiv)
  8. A. Alů, M. Young, and N. Engheta, “Design of Nanofilters for Optical Nanocircuits,” Physical Review B, Vol. 77, 144107 (12 pages), April 9, 2008, also in Virtual Journal of Nanoscale Science & Technology, Vol. 17, No. 16, April 21, 2008. (upenn, web, arxiv)
  9. M. G. Silveirinha, A. Alů, J. Li, and N. Engheta, “Nanoinsulators and Nanoconnectors for Optical Nanocircuits,” Journal of Applied Physics, Vol. 103, 064305 (24 pages), March 21, 2008. (upenn, web, arxiv)
  10. A. Alů, A. Salandrino, and N. Engheta, “Parallel, Series, and Intermediate Interconnections of Optical Nanocircuit Elements - Part 2: Nanocircuit and Physical Interpretation,” Journal of the Optical Society of America B, Vol. 24, No. 12, pp. 3014-3022, December 2007, also in Virtual Journal of Nanoscale Science & Technology, Vol. 17, No. 2, January 14, 2008. (web, arxiv)
  11. A. Salandrino, A. Alů, and N. Engheta, “Parallel, Series, and Intermediate Interconnections of Optical Nanocircuit Elements - Part 1: Analytical Solution,” Journal of the Optical Society of America B, Vol. 24, No. 12, pp. 3007-3013, December 2007, also in Virtual Journal of Nanoscale Science & Technology, Vol. 17, No. 2, January 14, 2008. (web, arxiv)
  12. A. Alů, A. Salandrino, and N. Engheta, “Coupling of Optical Lumped Nanocircuit Elements and Effects of Substrates,” Optics Express, Vol. 15, No. 21, pp. 13865-13876, October 2007. (upenn, web, arxiv)
  13. A. Alů, and N. Engheta, “Optical 'Shorting Wires',” Optics Express, Vol. 15, No. 21, pp. 13773-13782, October 2007, also in Virtual Journal of Nanoscale Science & Technology, Vol. 16, No. 19, November 5, 2007. (upenn, web, arxiv)
  14. A. Alů, and N. Engheta, “Three-Dimensional Nanotransmission Lines at Optical Frequencies: a Recipe for Broadband Negative-Refraction Optical Metamaterials,” Physical Review B, Vol. 75, 024304 (20 pages), January 19, 2007, also in Virtual Journal of Nanoscale Science & Technology, Vol. 15, No. 5, February 5, 2007. (upenn, web, arxiv)
  15. A. Alů, and N. Engheta, “Theory of Linear Chains of Metamaterial/Plasmonic Particles as Sub-Diffraction Optical Nanotransmission Lines,” Physical Review B, Vol. 74, 205436 (18 pages), November 29, 2006, also in Virtual Journal of Nanoscale Science & Technology, Vol. 14, No. 24, Dec. 11, 2006. (upenn, web, arxiv)
  16. A. Alů, and N. Engheta, “Optical Nano-Transmission Lines: Synthesis of Planar Left-Handed Metamaterials in the Infrared and Visible Regimes,” Journal of the Optical Society of America B, Special Focus Issue on Metamaterials, Vol. 23, No. 3, pp. 571-583, March 2006, (invited paper). (upenn, web, arxiv)
  17. N. Engheta, A. Salandrino, and A. Alů, “Circuit Elements at Optical Frequencies: Nanoinductors, Nanocapacitors and Nanoresistors,” Physical Review Letters, Vol. 95, 095504 (4 pages), August 26, 2005, also in Virtual Journal of Nanoscale Science & Technology, Vol. 12, No. 10, Sept. 5, 2005. (upenn, web, arxiv)

Optical Nanoantennas

The nanocircuit concepts may be applied to model and design optical nanoantennas, mimicking the functionalities of RF antennas at frequencies for which bandwidths and speed-rates may be increased by orders of magnitude. We have proposed the concepts of nanoantenna input impedance, optical radiation resistance, matching and loading of nanoantennas using nanocircuit loads. These concepts may enormously facilitate the design and use of optical nanoradiators, both as transmitters and as receivers.


An optical nanodipole fed by a plasmonic waveguide, all made of silver

To learn more:

  1. A. Alů, and N. Engheta, “Wireless at the Nanoscale: Optical Interconnects Using Matched Nanoantennas,” under review, since January 2010.
  2. A. Alů, and N. Engheta, “On Certain Design Criteria for Nanoantennas in the Visible,” Journal of Computational and Theoretical Nanoscience, Special Issue on Functional Nanophotonics and Nanoelectromagnetics, Vol. 6, No. 9, pp. 2009-2015, 2009, (invited paper).
  3. A. Alů, and N. Engheta, “Hertzian Plasmonic Nanodimer as an Efficient Optical Nanoantenna,” Physical Review B, Vol. 78, No. 19, 195111 (6 pages), November 13, 2008, also in Virtual Journal of Nanoscale Science & Technology, Vol. 18, No. 21, November 24, 2008. (upenn, web, arxiv) [One figure in this manuscript has been selected for the Physical Review B Kaleidoscope]
  4. A. Alů, and N. Engheta, “Input Impedance, Nanocircuit Loading, and Radiation Tuning of Optical Nanoantennas,” Physical Review Letters, Vol. 101, 043901, July 21, 2008, also in Virtual Journal of Nanoscale Science & Technology, Vol. 18, No. 5, August 4, 2008. (upenn, web, arxiv)
  5. A. Alů, and N. Engheta, “Tuning the Scattering Response of Optical Nanoantennas with Nanocircuit Loads,” Nature Photonics, Vol. 2, pp. 307-310, April 20, 2008. (web) [A News and Views highlighting our findings has appeared on Nature Photonics]

Energy Squeezing and Supercoupling

Anomalous tunneling, enhanced transmission and dramatic energy squeezing through narrow bends and channels may be obtained by exploiting the anomalous properties of zero-index materials, with interesting potentials for efficient power absorption, improved sensing and supercoupling applications. These concepts may be applied to metamaterial-inspired geometries, such as hollow channels at cut-off and optical waveguides, with interesting potentials in many fields of applied research.


Supercoupling and energy squeezing across a 90 degree squeezing and bending subwavelength ENZ channel in a rectangular waveguide at microwaves (from [4])

To learn more:

  1. A. Alů, and N. Engheta, “Coaxial-to-Waveguide Matching with ε-Near-Zero Ultranarrow Channels and Bends,” IEEE Transactions on Antennas and Propagation, in press.
  2. A. Alů, and N. Engheta, “Boosting Molecular Fluorescence with a Plasmonic Nanolauncher,” Physical Review Letters, Vol. 103, No. 4, 043902, July 21, 2009, also in Virtual Journal of Nanoscale Science & Technology, Vol. 20, No. 5, August 3, 2009. (web)
  3. D. A. Powell, A. Alů, B. Edwards, A. Vakil, Y. S. Kivshar, and N. Engheta, "Nonlinear Control of Tunneling Through an ε-Near-Zero Channel," Physical Review B, Vol. 79, No. 24, 245135 (5 pages), June 29, 2009. (web, arxiv)
  4. B. Edwards, A. Alů, M. G. Silveirinha, and N. Engheta, “Reflectionless Sharp Bends and Corners in Waveguides Using Epsilon-Near-Zero Effects,” Journal of Applied Physics, Vol. 105, No 4, 044905 (4 pages), February 18, 2009. (web, arxiv)
  5. A. Alů, and N. Engheta, “Light Squeezing through Arbitrarily-Shaped Plasmonic Channels and Sharp Bends,” Physical Review B, Vol. 78, 035440 (6 pages), July 24, 2008. (upenn, web, arxiv)
  6. A. Alů, M. G. Silveirinha, and N. Engheta, “Transmission-Line Analysis of ε-Near-Zero (ENZ)-Filled Narrow Channels,” Physical Review E, Vol. 78, 016604 (10 pages), July 23, 2008. (upenn, web, arxiv)
  7. A. Alů, and N. Engheta, “Dielectric Sensing in ε-Near-Zero Narrow Waveguide Channels,” Physical Review B, Vol. 78, 045102 (5 pages), July 3, 2008. (upenn, web, arxiv)
  8. B. Edwards, A. Alů, M. E. Young, M. G. Silveirinha, and N. Engheta, “Experimental Verification of Epsilon-Near-Zero Metamaterial Coupling and Energy Squeezing Using a Microwave Waveguide,” Physical Review Letters, Vol. 100, 033903, January 25, 2008. (upenn, web)

Negative-Index Optical Metamaterials

The concepts of optical nanocircuits may be applied to synthesize compact magnetic resonators in the visible, at frequencies for which conductivity and magnetism are challenging to realize. These ideas may lead to the synthesis of purely magnetic inclusions for the realization of negative-index optical metamaterials.


Electric field distribution for a resonant nanoloop composed of plasmonic particles, acting as lumped nanoinductors, interleaved by nano gaps acting as nanocapacitors. The loop may support a sub-wavelength magnetic resonance that may be employed for optical negative-index metamaterials (from [3])

To learn more:

  1. A. Alů, and N. Engheta, “The Quest for Magnetic Plasmons at Optical Frequencies,” Optics Express, Vol. 17, No. 7, pp. 5723-5730, March 25, 2009. (web)
  2. A. Alů, and N. Engheta, “Dynamical Theory of Artificial Optical Magnetism Produced by Rings of Plasmonic Nanoparticles,” Physical Review B, Vol. 78, 085112 (10 pages), August 11, 2008. (upenn, web, arxiv)
  3. A. Alů, and N. Engheta, “Negative Refraction in IR and Visible Domains,” in Handbook of Artificial Materials, F. Capolino, ed., Taylor and Francis - CRC Press, Vol. 1, in press.
  4. A. Alů, A. Salandrino, and N. Engheta, “Negative Effective Permeability and Left-Handed Materials at Optical Frequencies,” Optics Express, Vol. 14, No. 4, pp. 1557-1567, February 20, 2006, also in Virtual Journal of Nanoscale Science & Technology, Vol. 13, No. 19, May 15, 2006. (upenn, web, arxiv)

Zero-Index Metamaterials

The fascinating properties of zero-index and/or low-permittivity materials are not limited to cloaking and supercoupling applications, but also to a wide range of applied technology. We have suggested the application of their anomalous electromagnetic properties to tailor the phase patterns in various antenna geometries and to increase the directivity and the transmission through ultrassmall apertures.


The electric field distribution of the backward leaky-wave mode traveling along a low-permittivity cylindrical leaky-wave antenna, fed by a regular coaxial line (from [1])

To learn more:

  1. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Theory and Simulations of a Conformal Omni-Directional Sub-Wavelength Metamaterial Leaky-Wave Antenna,” IEEE Transactions on Antennas and Propagation, Vol. 55, No. 6, Part 2, pp. 1698-1708, June 2007. (upenn, web)
  2. A. Alů, M. G. Silveirinha, A. Salandrino, and N. Engheta, “Epsilon-Near-Zero Metamaterials and Electromagnetic Sources: Tailoring the Radiation Phase Pattern,” Physical Review B, Vol. 75, 155410 (13 pages), April 11, 2007, also in Virtual Journal of Nanoscale Science & Technology, Vol. 15, No. 16, April 23, 2007. (upenn, web, arxiv)
  3. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Sub-Wavelength Planar Leaky-Wave Components with Metamaterial Bilayers,” IEEE Transactions on Antennas and Propagation, Vol. 55, No. 3, Part 2, pp. 882-891, March 2007. (upenn, web)
  4. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Employing Metamaterial Layers to Increase Wave Transmission through a Sub-Wavelength Hole in a Flat Perfectly Conducting Screen,” in New Frontiers in Radiation Phenomena: a Tribute to Arthur Oliner, F. Frezza and P. Lampariello, eds., pp. 121-128, Edizioni Borgia, 2007.
  5. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Metamaterial Covers over a Small Aperture,” IEEE Transactions on Antennas and Propagation, Vol. AP-54, No. 6, pp. 1632-1643, June 2006. (upenn, web, arxiv)
  6. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “A Review on the Potential Employment of Metamaterial Layers for Increasing the Transmission through a Single Sub-Wavelength Aperture in a Flat Opaque Screen,” in Periodic Structures, M. Bozzi, S. Perregrini, eds., Ch. 10, pp. 271-292, Research Signpost Ed., 2006. (web)
  7. A. Alů, and F. Bilotti, “L’impiego di Metamateriali per Aumentare Considerevolmente la Trasmissione attraverso un Piccolo Foro in uno Schermo Opaco,” Quaderni di Elettromagnetismo, Vol. 1, No. 2, pp. 1-7, July 2005. (pdf, web)
  8. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Metamaterial Monolayers and Bilayers for Enhanced Transmission through a Sub-Wavelength Aperture in a Flat Perfectly Conducting Screen,” Atti della Fondazione Giorgio Ronchi, Vol. LX, No. 1-2, pp. 185-190, January-April 2005. (upenn, web)
  9. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Power-Transmission Enhancement through a Sub-Wavelength Hole in a Perfect Conductor by Employing Metamaterials,” Atti della Fondazione Giorgio Ronchi, Vol. LIX, No. 1-2, pp. 259-260, January-April 2004.

Metamaterial Antennas

The anomalous features of metamaterials may be applied to several antenna geometries at radio frequencies, in order to enhance their radiation performance and reducing their size. Resonant antennas beating the diffraction limit and superdirective radiators have been designed based on these concepts.


Electric field distribution around a metamaterial-loaded sub-wavelength patch antennas

To learn more:

  1. P. Y. Chen, and A. Alů, “Dual-Mode Miniaturized Elliptical Patch Antenna with μ-Negative Metamaterials” IEEE Antennas and Wireless Propagation Letters, under review, since January 2010.
  2. P. Y. Chen, and A. Alů, “Sub-Wavelength Elliptical Patch Antenna Loaded with μ-Negative Metamaterials,” under review, since November 2009.
  3. L. Vegni, F. Bilotti, A. Alů, and N. Engheta, “Application of Metamaterials to Microwave Patch and Leaky-Wave Antennas,” in Handbook of Artificial Materials, F. Capolino, ed., Taylor and Francis - CRC Press, Vol. 2, in press.
  4. F. Bilotti, A. Alů, N. Engheta, A. Toscano, and L. Vegni, “Metamaterial Based Microwave Components with Enhanced Features and Miniaturized Dimensions,” under review (since March 2007).
  5. F. Bilotti, A. Alů, and L. Vegni, “Design of Miniaturized Metamaterial Patch Antennas with µ-Negative Loading,” IEEE Transactions on Antennas and Propagation, Vol. 56, No. 6, pp. 1640-1647, June 2008. (web)
  6. A. Alů, and N. Engheta, “Enhanced Directivity from Sub-Wavelength Infrared/Optical Nano-Antennas Loaded with Plasmonic Materials or Metamaterials,” IEEE Transactions on Antennas and Propagation, Special Issue on Optical and Terahertz Antenna Technology, Vol. 55, No. 11, pp. 3027-3039, November 2007. (upenn, web)
  7. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Theory and Simulations of a Conformal Omni-Directional Sub-Wavelength Metamaterial Leaky-Wave Antenna,” IEEE Transactions on Antennas and Propagation, Vol. 55, No. 6, Part 2, pp. 1698-1708, June 2007. (upenn, web)
  8. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Sub-Wavelength Planar Leaky-Wave Components with Metamaterial Bilayers,” IEEE Transactions on Antennas and Propagation, Vol. 55, No. 3, Part 2, pp. 882-891, March 2007. (upenn, web)
  9. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Sub-Wavelength, Compact, Resonant Patch Antennas Loaded with Metamaterials,” IEEE Transactions on Antennas and Propagation, Vol. 55, No. 1, pp. 13-25, January 2007. (upenn, web)
  10. A. Alů, F. Bilotti, N. Engheta, and L. Vegni, “Metamaterial Grounded Planar Bilayers Supporting Leaky Waves: Principles and Applications,” Automatika, Journal for Control, Measurement, Electronics, Computing and Communications, Vol. 47, No. 3-4, pp. 127-131, 2006, (invited paper). (pdf, web)
  11. F. Bilotti, M. Manzini, A. Alů, and L. Vegni, “Polygonal Patch Antennas with Reactive Impedance Surfaces,” Journal of Electromagnetic Waves and Applications, Vol. 20, No. 2, pp. 169-182, 2006. (web)
  12. F. Bilotti, A. Alů, N. Engheta, and L. Vegni, “Anomalous Properties of Scattering from Cavities Partially Loaded with Double-Negative or Single-Negative Metamaterials,” in Progress in Electromagnetics Research, Special Issue on Metamaterials, Jin Au Kong, ed., Vol. 51, pp. 49-63, 2005. (upenn, pdf, web)

Sub-diffraction in Plasmonics and Metamaterials

The anomalous localized resonances that metamaterials and plasmonic media support when interfaced with regular materials may be exploited to overcome some intrinsic diffractive limitations in guiding and radiating nanodevices and to tailor the optical response of nanostructures. We have proposed several solutions at optical, IR and radio frequencies that exploit these concepts to realize novel sub-diffractive or superdirective waveguides, scatterers and antennas.


Field distribution inside and around superdirective nanoparticles at resonance (from [2])

To learn more:

  1. A. Alů, and N. Engheta, “Anomalies of Sub-Diffractive Guided-Wave Propagation along Metamaterial Nanocomponents,” Radio Science, Special Issue on Analytical Scattering and Diffraction, Vol. 42. No. 6, RS6S17, November 7, 2007. (upenn, web)
  2. A. Alů, and N. Engheta, “Enhanced Directivity from Sub-Wavelength Infrared/Optical Nano-Antennas Loaded with Plasmonic Materials or Metamaterials,” IEEE Transactions on Antennas and Propagation, Special Issue on Optical and Terahertz Antenna Technology, Vol. 55, No. 11, pp. 3027-3039, November 2007. (web)
  3. A. Alů, and N. Engheta, “Higher-Order Resonant Power Flow Inside and Around Superdirective Plasmonic Nanoparticles,” Journal of the Optical Society of America B, Special Issue on Photonic Metamaterials: from Random to Periodic, Vol. 24, No. 10, pp. A89-A97, October 2007, also in Virtual Journal of Biomedical Optics, Vol. 2, No. 11, November 26, 2007. (upenn, web)
  4. A. Alů, and N. Engheta, “Polarizabilities and Effective Parameters for Collections of Spherical Nano-Particles Formed by Pairs of Concentric Double-Negative (DNG), Single-Negative (SNG) and/or Double-Positive (DPS) Metamaterial Layers,” Journal of Applied Physics, Vol. 97, 094310 (12 pages), May 1, 2005 (erratum in Journal of Applied Physics, Vol. 99, 069901, March 15, 2006). (upenn, web, arxiv)
  5. A. Alů, and N. Engheta, “An Overview of Salient Properties of Planar Guided-Wave Structures with Double-Negative (DNG) and Single-Negative (SNG) Layers,” in Negative Refraction Metamaterials: Fundamental Properties and Applications, G. V. Eleftheriades, and K. G. Balmain, eds., Ch. 9, pp. 339-380, IEEE Press, John Wiley & Sons Inc., Hoboken, New Jersey, 2005. (web)
  6. A. Alů, and N. Engheta, “Guided Modes in a Waveguide Filled with a Pair of Single-Negative (SNG), Double-Negative (DNG), and/or Double-Positive (DPS) Layers,” IEEE Transactions on Microwave Theory and Techniques, Vol. 52, No. 1, pp. 199-210, January 2004. (upenn, web)

Metamaterial Physics and Technology

We have been interested in the anomalous physics and phenomena associated with metamaterials and nanomaterials, investigating several aspects of metamaterial nanotechnology and the fundamental physical reasons underneath their anomalous electromagnetic behavior. Anomalous wave and optical phenomena and their intrinsic limitations have been underlined in different geometries at the nanoscale.


Sub-diffraction virtual imaging through a metamaterial resonant bilayer analyzed with FDTD (from [5])

To learn more:

  1. I. Gallina, G. Castaldi, V. Galdi, A. Alů, and N. Engheta, “A General Class of Metamaterial Transformation Slabs,” under review, since November 2009. (arxiv)
  2. Y. Li, A. Alů, and H. Ling, "Simulation and Measurement of Surface Wave Propagation along a Metal Cut-Wire Array," under review, since August 2009.
  3. A. Alů, N. Engheta, A. Erentok, and R. W. Ziolkowski, “Single-Negative, Double-Negative and Low-Index Metamaterials and their Electromagnetic Applications,” IEEE Antennas and Propagation Magazine, Vol. 49, No. 1, pp. 23-37, February 2007, (invited paper). (upenn, web)
  4. A. Alů, F. Bilotti, and L. Vegni, “Analysis of L-L Transmission Line Metamaterials with Coupled Inductances,” Microwave and Optical Technology Letters, Vol. 49, No. 1, pp. 94-97, January 2007. (web)
  5. A. Alů, F. Bilotti, and L. Vegni, “Exploring the Possibility of Enhancing the Bandwidth of μ-Negative Metamaterials by Employing Tunable Varactors,” Microwave and Optical Technology Letters, Vol. 49, No. 1, pp. 55-59, January 2007. (web)
  6. A. Alů, N. Engheta, A. Erentok, and R. W. Ziolkowski, “Single-Negative, Double-Negative and Low-Index Metamaterials and their Electromagnetic Applications,” Radio Science Bulletin, Vol. 319, pp. 6-19, December 2006, (invited paper). (pdf, web)
  7. A. Alů, N. Engheta, and R. W. Ziolkowski, “Finite-Difference Time-Domain Analysis of the Tunneling and Growing Exponential in a Pair of ε-negative and μ-negative Slabs,” Physical Review E, Vol. 74, 016604 (9 pages), July 18, 2006.  (upenn, web, arxiv)
  8. A. Alů, and N. Engheta, “Physical Insight into the 'Growing' Evanescent Fields of Double-Negative Metamaterial Lenses Using their Circuit Equivalence,” IEEE Transactions on Antennas and Propagation, Vol. 54, No. 1, pp. 268-272, January 2006. (upenn, web, arxiv)
  9. N. Engheta, and A. Alů, “Selected Features of Metamaterials and Plasmonic Media,” Atti della Fondazione Giorgio Ronchi, Vol. LX, No. 1-2, pp. 165-170, January-April 2005. (web)
  10. A. Alů, and N. Engheta, “‘Evanescent Growth and Tunneling through Stacks of Frequency-Selective Surfaces,” IEEE Antennas and Wireless Propagation Letters, Vol. 4, pp. 417-420, 2005. (upenn, web, arxiv)
  11. N. Engheta, A. Alů, R. W. Ziolkowski, A. Erentok, “Fundamentals of Waveguide and Antenna Applications involving DNG and SNG Metamaterials,” in Metamaterials: Physics and Engineering Explorations, N. Engheta and R. Ziolkowski, eds., Ch. 2, pp. 43-86, IEEE Press, John Wiley and Sons, Inc., 2006. (web)
  12. A. Alů, and N. Engheta, “Pairing an Epsilon-Negative Slab with a Mu-Negative Slab: Anomalous Tunneling and Transparency,” IEEE Transactions on Antennas and Propagation, Special Issue on Metamaterials, Vol. 51, No. 10, pp. 2558-2570, October 2003, (invited paper). (upenn, web)
  13. A. Alů, F. Bilotti, and L. Vegni, “Chiral and EBG Materials: Electromagnetic Applications,” Atti della Fondazione Giorgio Ronchi, Vol. LVIII, No. 3-4, pp. 459-463, May-June 2003. (web)
  14. A. Alů, and N. Engheta, “Radiation from a Traveling-Wave Current Sheet at the Interface between a Conventional Material and a Metamaterial with Negative Permittivity and Permeability,” Microwave and Optical Technology Letters, Vol. 35, No. 6, pp. 460-463, December 20, 2002. (upenn, web)

Antenna Technology, Theoretical and Numerical Electromagnetics

Antenna design is well established at radio frequencies, but the application of novel technological concepts, like transmission-line metamaterials, nanoengineered materials or compact sub-wavelength resonators, may suggest novel techniques to enhance their performance, as we have shown in several recent works. In parallel, the fundamental concepts of RF antennas may be scaled in frequency to optimize the design of nanoantennas and plasmonic nanstructures. In this sense, our interest in the theoretical and numerical aspects of classic electromagnetic theory has proven to be fundamental in several different research problems.


A conformal patch antenna discretized with the E-MoL technique (from [6])

To learn more:

  1. A. Alů, and S. Maslovski “Power Relations and a Consistent Analytical Model for Receiving Wire Antennas,” IEEE Transactions on Antennas and Propagation, in press.
  2. A. Alů, C. Sapia, A. Toscano, and L. Vegni “Radio-Frequency Animal Identification: Electromagnetic Analysis and Experimental Evaluation of the Transponder-Gate System,” International Journal of Radio Frequency Identification Technology and Applications, Vol. 1, No. 1, pp. 90-106, August 2006. (web)
  3. F. Bilotti, M. Manzini, A. Alů, and L. Vegni, “Polygonal Patch Antennas with Reactive Impedance Surfaces,” Journal of Electromagnetic Waves and Applications, Vol. 20, No. 2, pp. 169-182, 2006. (web)
  4. F. Bilotti, A. Alů, F. Urbani, and L. Vegni, “Asymptotic Evaluation of the MoM Excitation Vector for Probe-Fed Microstrip Antennas,” Journal of Electromagnetic Waves and Applications, Vol. 19, No. 12, pp. 1639-1654, December 2005. (web)
  5. F. Urbani, F. Bilotti, A. Alů, and L. Vegni, “VCO Active Integrated Antenna with Reactive Impedance Surfaces,” Microwave and Optical Technology Letters, Vol. 47, No. 1, pp. 82-86, October 5, 2005. (web)
  6. A. Alů, F. Bilotti, A. Toscano, and L. Vegni “Analysis of Signal Integrity and Electromagnetic Interference of High-Speed Digital Systems,” Atti della Fondazione Giorgio Ronchi, Vol. LX, No. 1-2, pp. 383-387, January-February 2005. (web)
  7. M. Manzini, A. Alů, F. Bilotti, and L. Vegni “Polygonal Patch Antennas for Wireless Communications,” IEEE Transactions on Vehicular Technology, Vol. 53, No. 5, pp. 1434-1440, September 2004. (web)
  8. A. Alů, F. Bilotti, and L. Vegni, “Method of Lines Numerical Analysis of Conformal Antennas,” IEEE Transactions on Antennas and Propagation, Vol. 52, No. 6, pp. 1530-1540, June 2004. (web)
  9. A. Alů, F. Bilotti, M. Manzini, and L. Vegni “On the Employment of Edge Basis Functions to Improve the Analysis of Polygonal Patches,” Journal of Electromagnetic Waves and Applications, Vol. 18, No. 3, pp. 397-410, February 2004. (web)
  10. M. Manzini, F. Bilotti, A. Alů, and L. Vegni “Design of Broad-Band Polygonal Patch Antennas for Mobile Communications,” Journal of Electromagnetic Waves and Applications, Vol. 18, No. 1, pp. 61-72, January 2004. (web)
  11. A. Alů, L. Vegni, and F. Bilotti, “Current Density Dominant Mode on Spiral Patch Antennas,” Automatika, Journal for Control, Measurement, Electronics, Computing and Communications, Vol. 45, no. 1-2, pp. 29-32, 2004. (pdf, web)
  12. F. Bilotti, A. Alů, and L. Vegni, “Electromagnetic Field Solution in Conformal Structures: Theoretical and Numerical Analysis,” in Progress in Electromagnetics Research, Jin Au Kong, ed., Vol. 47, pp. 1-25, 2004. (pdf, web)
  13. A. Alů, F. Bilotti, and L. Vegni, “Generalized Transmission Line Equations for Bianisotropic Materials,” IEEE Transactions on Antennas and Propagation, Vol. AP-51, No. 11, pp. 3134-3141, November 2003. (web)
  14. A. Alů, F. Bilotti, and L. Vegni, “Extended Method of Line Procedure for the Analysis of Microwave Components with Bianisotropic Inhomogeneous Media,” IEEE Transactions on Antennas and Propagation, Vol. 51, No. 7, pp. 1582-1589, July 2003. (web)
  15. L. Vegni, A. Alů, and F. Bilotti, “Electromagnetic Field Solution in Curved Structures with Local Bianisotropic Loading Media,” in Advances in Electromagnetics of Complex Media and Metamaterials, NATO Science Series Book, S. Zouhdi, A. Sihvola, and M. Arsalane, eds., Vol. 89, pp. 439-448, Kluwer Academic Publisher, The Netherlands, 2003. (web)
  16. A. Alů, F. Bilotti, and L. Vegni, “Generalized Telegraphers’ and Helmholtz Equations for Conformal Structures with Bi-anisotropic Loading Materials,” Journal of Electromagnetic Waves and Applications, Vol.16, No.8, pp. 1061-1075, August 2002.
  17. F. Bilotti, L. Vegni, and A. Alů, “Radiation Properties of Rectangular Patch Antennas with Inhomogeneous Substrates via a MoM Formulation,” Journal of Electromagnetic Waves and Applications, Vol.16, No.6, pp. 871-881, June 2002.
  18. A. Alů, F. Bilotti, and L. Vegni, “Design of Chiral Planar Integrated Antennas with Cover via the Method of Lines,” Microwave and Optical Technology Letters, Vol. 32, No. 2, pp.143-145, January 20, 2002. (web)
  19. F. Bilotti, L. Vegni, and A. Alů, “U-Patch Antenna Loaded by Complex Substrates for Multi-Frequency Operation,” Microwave and Optical Technology Letters, Vol. 32, No. 1, pp.3-5, January 5, 2002. (web)

upenn refers to the pdf repository at the University of Pennsylvania
arxiv refers to the public pre-print website at the Cornell University
pdf refers to a freely available pdf copy of the original paper
web links to the journal website, where a copy of the paper may be downloaded

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