Workshops


Tuesday, December 20th
08:30-10:00 Graphene: mm-wave and THz amplification and Optical NonlinearityBy: Prof. Hamed Majedi

Graphene offers a cornucopia of beautiful physics and technological applications owing to its topological properties and relativistic features in electronic band structure. Graphene electronic and photonic properties have generated lots of interest although its integration, interfacing, contacting and fabrication compatibility needs careful considerations. In this workshop, I will focus on two applications, mm-wave/THz amplification and optical nonlinearity. In the first application, I consider a graphene layer that is integrated into slow-wave mm-wave/THz waveguiding structure to develop a traveling-wave amplification. I will use a relativistic hydrodynamic model based on Boltzmann’s transport to model a graphene layer. Then this model is coupled to Maxwell’s equations to analyze the traveling-wave structure in a self-consistent way. Our experimental approach to make such an amplifier is lastly introduced. In the second application, the optical nonlinearity of graphene based on semi-classical treatment is briefly introduced and our numerical results for Kerr nonlinearity versus wavelength and Fermi potential are discussed. I introduce the integration of graphene with photonic band gap structure to develop tunable and nonlinear photonic integrated circuits. Last but not least, our experimental setups including resonant reflection measurement with confocal microscopy and z-scan along with initial results are demonstrated

10:30-12:00 Electrically-Small Resonators as the Lego of Electromagnetic Systems By: By Prof. Omar Ramahi

When Smith, Pendry and others started tinkering with split-ring resonators (SRR) for realizing double negative media, little did we know then that these earlier ground breaking works ushered the beginning of a completely different perspective on designing all types of electromagnetics-based systems. The SRR, or any other resonator that has dimensions much smaller than the wavelength were used as the building blocks for single and double negative media and even near-zero media. While these exotic media enabled cloaking and design of dispersion-controlled media, the applications were largely limited. The concept of a building block, however, might hold the key to a much larger class of designs and applications. Back in the seventeenth century, Huygens conceived the idea of elementary sources as forming the radiated or scattered field. His extraordinary perception of the mechanism of the wave phenomenon preceded the full-fledged development of Maxwell equations by more than 150 years. While Huygens work was an attempt to understand the wave phenomenon through analysis, we pose the question of whether we can extend the concept of building blocks or elementary sources to synthesize electromagnetics based radiating systems. If all things in nature are composed of identical building blocks, can we conceive of a similar construction of electromagnetics systems in general? In this workshop, I will focus on the importance of understanding what is meant by metamaterial, metasurface particles or electrically-small resonators in general. Unlike building blocks used for other physical systems that are not founded on the action-at-a-distance phenomena, the electrically-small resonators, or electromagnetic Legos are more intriguing as their strong coupling needs to be tailored to ensure their desired operation. Several new designs of electromagnetics systems from lenses, to sensors and antennas will be discussed in details covering a broad range of activities conducted in my research group at Waterloo. Focusing on the concept of a building block will naturally reignite strong interest in understanding the fundamental physical phenomenon of radiation and hopefully would lead to asking important questions that were considered of secondary importance in earlier times.

14:00-15:30 mm-wave Imaging for Security ApplicationsBy: Dr. Amirnader Askarpour

Electromagnetic radiation with a wavelength within the millimeter range can penetrate clothing, yet it reflects back from the surface of human tissue, metals, and some other important materials. This characteristic makes these waves suitable for full-body scanners, which can detect hidden objects under layers of clothing. The applications of such a device include government building and airport security checkpoints. In this workshop, the fundamental theory of imaging is described. We will start from well-known imaging examples in the optical regime and work our way down in frequency to the millimeter-waves. Significant wave phenomena occur in this regime, which needs careful consideration. After formulating the imaging problem with enough precision to account for low frequency effects, we study a few important experimental setups, which have led to some commercial products for security screening. Finally, recent developments throughout the world and in Iran regarding this technology is covered.

For more information please contact mmwatt [at] aut.ac.ir.