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Vladimir M. Shalaev
Robert and Anne Burnett Professor of Electrical and Computer Engineering and Professor of Biomedical Engineering
Professor Shalaev has received several awards for his research in the fields of nanophotonics and metamaterials. He is a Fellow of the American Physical Society (APS), a Fellow of The International Society for Optical Engineering (SPIE), and a Fellow of the Optical Society of America (OSA). Professor Shalaev is an editor or co-editor for five books in the area of nanophotonics, is a program chair for a number of international symposia and conferences, and is co-editor and/or an editorial board member for eight research journals. In total, Vlad Shalaev has authored or co-authored three books, 21 invited book chapters and over 300 research publications.
One of the most unique properties of light is that it can package information into a signal of zero mass and propagate it at the ultimate speed. It is, however, a daunting challenge to bring photonic devices to the nanometer scale because of the fundamental diffraction limit. Metamaterials can focus light down to the nanoscale and thus enable a family of new nanophotonic devices. Metamaterials, i.e. artificial materials with rationally designed geometry, composition, and arrangement of nanostructured building blocks called meta-“atoms,” are expected to open a gateway to unprecedented electromagnetic properties and functionalities that are unattainable with naturally occurring materials. We review this exciting and emerging field and discuss the recent, significant progress in developing metamaterials for the optical part of the electromagnetic spectrum. Specifically, we describe the recently demonstrated phenomena of artificial magnetism across the whole visible and negative refractive indices in the optical range, and we discuss the promising approaches and central challenges in realizing optical cloaking. A new, powerful paradigm of engineering space for light with transformation optics will be also discussed.
Vlad Shalaev is known world-wide for his pioneering contributions to nanophotonics, the optics of nanocomposites including fractals and percolation systems, and optical metamaterials. During the last seven years, the Shalaev research group has conducted many critical theoretical analyses and has accomplished nanofabrication and seminal experimental work on optical metamaterials that exhibit negative refractive indices and magnetic responses at optical frequencies.
In the optical range, the magnetic response (permeability) for naturally occurring materials is very close to its free space value, indicating that natural materials have almost no magnetic response at optical frequencies. Before the year 2004, the shortest wavelength at which materials exhibited a significant magnetic response was on the scale of millimeters. Since 2004, researchers from various groups have fabricated and experimentally demonstrated various metamaterials with magnetic responses at wavelengths from 300 micrometers down into the near-infrared. However, the Shalaev group was the first to demonstrate artificial magnetism across the entire visible range. As a result of these breakthroughs in the field, the frequency range for materials with magnetism has been expanded by five orders of magnitude.
In the year 2005, the Shalaev research group demonstrated the first optical metamaterial with a negative refractive index at the telecommunication wavelength of 1.5 µm. This was the breakthrough demonstration of a negative refractive index in the optical range. This pioneering work was based on Vlad Shalaev and his co-authors’ earlier (in 2002) theoretical prediction that pairs of metal nanorods can provide a negative refractive index, which is exactly the structure that the Shalaev group used to demonstrate their first negative-index optical metamaterial. Almost simultaneously, Professors S. Brueck and R. Osgood used a physically equivalent “fishnet” structure to demonstrate a negative refractive index at a wavelength of 2 µm. Later, Professor Wegener used the same structure to obtain a negative refraction index at 780 nm. Most recently, Professor Shalaev’s group has demonstrated a metamaterial with a negative refractive index for yellow light, at 580 nm, which is currently the shortest wavelength at which a negative refractive index has been observed for light.
The Shalaev group has further extended the possible applications of optical metamaterials by showing the feasibility of cloaking objects in the visible range. Vlad Shalaev’s proposal of cloaking in the visible part of the spectrum is original and different from that proposed earlier by Pendry, Smith, et al., which is suitable only for the microwave range. Later, Shalaev’s group also suggested a high-order transformation method for cloaking, which allows one to remove any residual scattering resulting from an impedance mismatch. Most recently, Vlad Shalaev and his group suggested the idea of “cascaded” cloaks operating at multiple wavelengths, thus potentially enabling broadband invisibility. Finally, the Shalaev and Smolyaninov groups have recently demonstrated broadband cloaking in a specially tapered waveguide, which emulates well the metamaterial-based anisotropic cloak and thus verifies the Shalaev group’s idea for cloaking. Currently, the Shalaev group is working on novel approaches for engineering and controlling space for light based on transformation optics, a new paradigm for the science of light which is expected to result in a family of new “meta-devices.”