alex m. H. Wong

Tailoring Electromagnetic Near-Fields and Far-Fields with Active Directional Sources

In this talk we overview our works related to directional electromagnetic sources. Directional electromagnetic sources 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 unique and complementary application potentials. Particularly, we present our investigative results on the Janus source, which has emerged in the past 5-10 years. 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.

Alex M. H. Wong received his Ph.D. degree in 2014 from the University of Toronto, Canada. He is currently an Associate Professor with the Department of Electrical Engineering, City University of Hong Kong, where he is also a Member of the State Key Laboratory of Terahertz and Millimeter Waves. He has advanced multiple projects in applied electromagnetics on next-generation RF, infrared, and optical metasurfaces, super-resolution imaging and radar systems. His received accolades include an IEEE RWP King Award, the URSI Young Scientist Award, the Raj Mittra Grant, the IEEE Doctoral Research Awards from the AP and MTT societies, and the Canada Graduate Scholarship (doctoral level). He has served as the General Co-Chair for the 2025 International Workshop in Electromagnetics, the General Co-Chair for the 2022 IEEE HK AP-MTT Postgraduate Student Conference, and the TPC Vice-Chair for the 2020 Asia-Pacific Microwave Conference (APMC 2020), among others. He has published over 40 journal papers, including articles in leading journals such as Advanced Science, Physical Review X, Physical Review Letters and IEEE Transactions papers.