Prof. Andrea Alu
The University in Texas at Austin
Department of Electrical and Computer Engineering
201, Speedway ENS 431
Austin, TX 78712,
Metamaterials and Plasmonics to Tailor and Enhance Wave-Matter Interactions
Metamaterials and plasmonics offer unprecedented opportunities to tailor and enhance the interaction of waves with matter. In this lecture, I will discuss our recent progress and research activity in these research areas, showing how suitably tailored meta-atoms and combinations of them can open new venues to manipulate and control electromagnetic waves in unprecedented ways. I will discuss our recent theoretical and experimental results involving metamaterial and/or plasmonic nanostructures, including the concept of magnetic-based Fano resonances in nanoclusters, modularized optical nanocircuits, nanoantennas and metasurfaces to control light propagation and radiation, enhanced artificial magnetism and chirality in properly tailored metamaterials, parity-time symmetric metamaterials, giant nonlinearities and nonreciprocity using suitably designed meta-atoms. Physical insights into these exotic phenomena and their impact on technology and new electromagnetic devices will be discussed during the talk.
Cloaking and Invisibility Using Metamaterials and Metasurfaces
In this lecture, I will discuss our recent progress and research activity in using metamaterial covers to suitably tailoring the scattering of passive objects, drastically suppressing their overall detectability. I will focus on two approaches we have pioneered in the past years, the plasmonic cloaking and the mantle cloaking techniques, respectively based on bulk plasmonic metamaterials and ultrathin metasurfaces. I will show the theoretical concepts at the basis of these approaches and our experimental results at radio-waves, which represent the first experimental verification of cloaking for 3D free-standing objects. I will also discuss advanced concepts, such as the ultimate bounds on realizing ‘invisible sensors’, the general bounds and potentials of cloaking and invisibility on bandwidth and overall scattering reduction, and ways to overcome these limitations using active, non-Foster cloaks.
Homogenization of Electromagnetic Metamaterials
The proper modeling and homogenization of metamaterials is a crucial task to be able to apply them in practical devices and technology. This lecture will provide an overview and introduction to the theoretical aspects and challenges in the homogenization of metamaterials. After outlining the popular approaches to this problem, I will discuss the challenges and difficulties that metamaterials introduce in their rigorous electromagnetic homogenization. I will then review the recent advances in ‘homogenization theory’ introduced in my group in the past few years, and highlight the advantages of this approach with numerical and practical examples. The relevant issues of causality and passivity of the effective parameters of metamaterials will be discussed in detail and applied to practical electromagnetic problems of general interest.
Giant Non-Reciprocity / Non-Linearity Using Metamaterials
In this lecture, I will describe our recent theoretical and experimental advances in boosting the nonreciprocal and nonlinear response of subwavelength meta-molecules and arrays of them, applied to radio-waves, light and/or sound. I will first introduce the general concept of angular-momentum biased metamaterials, which support the analog to the Zeeman effect in ferromagnetic moulecules, but without relying on any magnetic effect. I will show that it is possible to induce large non-reciprocal response at the subwavelength scale by splitting the degenerate modes supported by a resonant meta-molecule applying an angular momentum bias, in the form of circulating media or azimuthally-symmetric spatiotemporal modulation. In this way, I will discuss how large nonreciprocal effects may be obtained in fully integrated designs that do not require magnetic bias, experimentally demonstrated for sound and radio-waves, and concepts to extend these effects also to infrared and nanophotonic systems. Within the same thrust, I will also discuss our recent theoretical and experimental progress in boosting the naturally weak non-linear response using metamaterials. We have recently pursued two promising venues in this direction: the use of extreme parameter metamaterials and the suitable engineering of combined electronic and photonic transitions in suitably designed metasurfaces. These concepts are shown to produce orders of magnitude enhancement in the efficiency of various non-linear optical processes, including second-harmonic generation, phase conjugation and frequency mixing, also relaxing the need for phase matching.
Andrea Alù is an Associate Professor and David & Doris Lybarger Endowed Faculty Fellow in Engineering at the University of Texas at Austin. He received the Laurea, MS and PhD degrees from the University of Roma Tre, Rome, Italy, respectively in 2001, 2003 and 2007. From 2002 to 2008, he has been periodically working at the University of Pennsylvania, Philadelphia, PA, where he has also developed significant parts of his PhD and postgraduate research. After spending one year as a postdoctoral research fellow at UPenn, in 2009 he joined the faculty of the University of Texas at Austin. He is also a member of the Applied Research Laboratories and of the Wireless Networking and Communications Group at UT Austin.
He is the co-author of an edited book on optical antennas, over 230 journal papers, 400 conference papers and over 20 book chapters. His current research interests span over a broad range of areas, including metamaterials and plasmonics, electromangetics, optics and photonics, scattering, cloaking and transparency, nanocircuits and nanostructures modeling, miniaturized antennas and nanoantennas, RF antennas and circuits.
Dr. Alù is currently on the Editorial Board of Scientific Reports and Advanced Optical Materials, he serves as Associate Editor of five journals, including the IEEE Antennas and Wireless Propagation Letters and of Optics Express. In the past few years he has guest edited special issues for the IEEE Journal of Selected Topics in Quantum Electronics, for Optics Communications, for Metamaterials and for Sensors on a variety of topics involving metamaterials, plasmonics, optics and electromagnetic theory. He has received several awards for his research activity, including the OSA Adolph Lomb Medal (2013), the IUPAP Young Scientist Prize in Optics (2013), the IEEE MTT Outstanding Young Engineer Award (2014), the Franco Strazzabosco Award for Young Engineers (2013), the URSI Issac Koga Gold Medal (2011), the SPIE Early Career Investigator Award (2012), an NSF CAREER award (2010), the AFOSR and the DTRA Young Investigator Awards (2010, 2011), Young Scientist Awards from URSI General Assembly (2005) and URSI Commission B (2010, 2007 and 2004). His students have also received several awards, including student paper awards at IEEE Antennas and Propagation Symposia and at the Metamaterials conference series. He has been elected an APS Outstanding Referee in 2013, he serves as OSA Traveling Lecturer since 2010 and as the IEEE joint AP-S and MTT-S chapter for Central Texas since 2011, and is a full member of URSI, a fellow of IEEE and of OSA and a senior member of SPIE.