State Key Laboratory of Terahertz and Millimeter Waves

(City University of Hong Kong)

Seminar on

Tailoring EM Waves with Discrete Metasurfaces and Active Electromagnetic Dipoles

Professor Alex M. H. Wong

Associate Professor

Department of Electrical Engineering

City University of Hong Kong

Date               : 29 November 2024 (Friday)

Time              : 11:15 am – 12:15 pm

Venue            : Room 6-208, 6/F, Lau Ming Wai Academic Building

Abstract

Electromagnetic meta-devices of various kinds have emerged in the last 20 years to manipulate electromagnetic waves with unprecedented freedom, implicating microwave to optical frequencies, enhancing our understanding on fundamental physical phenomena and finding applications in microscopy, biomedicine and wireless communication and power transfer, to name a few. In this talk, I will review recent progress in my research group in two main areas: the discrete metasurface and the directional electromagnetic source.

The discrete metasurface (aka the metagrating) is an approach to treat the metasurface as an inherently pixelated surface with spatially discrete electromagnetic properties. Through taking this approach, we understand how discretization changes the metasurface performance and to what degree the metasurface can tolerate discretization. In some cases, we can also achieve functionalities which are impossible or unobvious to the continuous metasurface. Aggressive discretization can help to enlarge the size of the meta-atom, enabling enhanced bandwidth, reduction of fabrication tolerance, the design of function-enhanced meta-atoms.

The directional electromagnetic source have attracted much recent attention as they form building blocks to meta-devices that manipulate the travel direction of electromagnetic waves. We juxtapose the near- and far-field properties of the circular, Huygens, and Janus dipoles, and show that the Huygens and Janus dipoles both exhibit directional near-field coupling behavior, but possess very different far-field radiation behaviors. This gives them complementary application potentials. While existing Janus dipoles are essentially sub-wavelength structures that scatter a small part of an incident wave, we introduce the Janus antenna – an active Janus dipole fed by a transmission line, which dramatically increases the power throughput and the bandwidth over which the near-field directional behavior can be achieved. The Janus dipole can be used as either an antenna a meta-device or a meta-atom, with promising potentials in directional switching, MIMO antenna and compact WPT systems.

Biography

Alex M. H. Wong (Senior Member, IEEE) received the Ph.D. degree from the University of Toronto, Canada in 2014. He is an Associate Professor in the Department of Electrical Engineering and a member of the State Key Laboratory of Terahertz and Millimeter Waves at the City University of Hong Kong. He has advanced multiple projects in applied electromagnetics on next-generation RF, infrared and optical metasurfaces, metasurface antennas and wireless power transfer systems. His received accolades include the IEEE RWP King Award, the URSI Young Scientist Award, the Raj Mittra Grant, IEEE Doctoral Research Awards from the AP and MTT Societies, and the Canada Graduate Scholarship (doctoral level).

*** ALL ARE WELCOME ***

Enquiries:

Professor Chi Hou Chan, State Key Laboratory of Terahertz and Millimeter Waves

Tel.: (852) 3442 9360 Fax: (852) 3442 0353 Email: eechic@cityu.edu.hk