The META Research Group performs leading-edge research in a variety of areas of microwave, terahertz and optical electromagnetics science and technology. Constantly exploring new horizons, it strives to pioneer some of the innovations that will shape tomorrow's landscape of human knowledge and evolution.
Bianisotropic metasurfaces may be seen as generalizations of the microwave frequency-selective surfaces or reflective/transmitting arrays and of the optical spatial light modulators. However, with their 36 bianisotropic surface susceptibilitity parameters, they allow for unprecedented and virtually unlimited electromagnetic wave transformations. This is particularly the case since our development of universal synthesis techniques, based on Generalized Sheet Transition Conditions (GSTCs), which allow for incredibly diverse and complex wave designs, including the possibility of multiple transformations. Bianisotropic metasurfaces are thus poised to revolutionize millimeter-wave and photonics technology. We are currently writing the first textbook on this topic, and this book is expected to be published by the end of 2020.
Spacetime metamaterials are artificial materials whose parameters vary both in space and time so as to allow simultaneous and sophisticated manipulations of the spatial spectra (directions) and temporal spectra (frequencies) of electromagnetic waves. Time modulation represents a fundamental extra dimension that dramatically enhances the diversity of conventional metamaterials. Spacetime metamaterials may be subluminal or superluminal and interluminal. We have already demonstrated them in a few exotic of applications, such as inverse prisms, shifted-time reversers, pulse companders and spacetime photonic crystals. We believe that they have a huge potential that will be soon unveiled.
Nonreciprocity is a fundamental concept in all the branches of physics, where it underpins a myriad of phenomena and applications. Since World War II, electromagnetic nonreciprocal devices have been almost exclusively based on ferrimagnetic materials (ferrites) biased by permanent magnets, although this technology suffers from severe issues, such as crystallographic incompatibility with semiconductors. Over the past decade, advances in metamaterial research have initiated a real quest for “magnetless” nonreciprocity, i.e. for novel technologies requiring neither ferrimagnetic materials nor magnets and yet exhibiting the same properties as ferrite systems, and even many more! Our group is at the forefront of this research area, which we initiated with the first magnetless Faraday metamaterial in 2011.
Optical Force Engineering
Kepler discovered the optical force in 1607 by observing the deflection of the tail of comets away from the sun and poetically wrote to Galileo in 1608: "Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void." Indeed, solar sails are currently used by space agencies to propel spacecrafts. However, the conventional sails only provide a pushing force away from the light source. Leveraging latest metamaterial concepts, we have introduced solar sails that offer in addition rotative, lateral and even attractive optical forces. Such opportunities do not exist only in the immensity of deep space! They also pertain to the nano-world, where we are developing highly sophisticated forces to manipulate small electronic and biological substances with unprecedented flexibility, opening light manipulation horizons well beyond those of the Nobel Prize winning optical tweezers of Arthur Ashkin.
Leaky-wave antennas are kind of scanning diffraction gratings excited within their plane, and their operation is similar to Cerenkov radiation. They have a history of over seven decades and offer the powerful capability of radiating across space in terms of beams whose directions can be tune by simple frequency or electric tuning. However, it is only with the advent of metamaterials that they have been started to reach their full potential. We have recently described them in fundamental terms of symmetries, including PT symmetry balance at broadside, and developed related communication, radar, instrumentation and imaging applications. Much further development is expected in the forthcoming decades in this quasi inexhaustible research area.
“The important thing is not to stop questioning.”