您的位置 : 讲座时间：2018年3月9日上午9:30
讲座地点：玉泉校区行政楼111会议室
1
1
Talk 1: Imaging Beyond the Diffraction Limit with Superoscillatory Electromagnetic Waves
Conventional imaging systems based on electromagnetic (EM) waves suffer a resolution limit due to wave dispersion and diffraction characteristics: the resolution is limited to roughly half the wavelength of the illumination wave. This is, for example, the reason why a Blu-ray Disc (written by a blue laser) contains higher information density than a DVD (written by a red laser, which has a longer wavelength than blue). In this seminar will first examine the cause of the aforementioned diffraction limits, then briefly survey some proposed solutions (prior to or in parallel with my work). We will then examine the curious phenomenon of superoscillation, which, for example, allows red light to oscillate as sharply as blue light for a designated stretch of space, and hence increases its resolution. I shall explain several projects I undertook in this area, which show that superoscillation makes a viable and attractive avenue to achieving super-resolution imaging in time and space, in a manner which bypasses common drawbacks suffered by other super-resolution systems. Along the way I shall also mention how these systems can potentially benefit from the deployment of metasurfaces.
Talk 2: Bipartite Huygens’ Metasurfaces and the Huygens’ Box: Frontiers in Electromagnetic Metasurfaces
The metasurface is an emerging technology that enables one to generate and control EM waves with great flexibility. Whilst ample contemporary works have investigated planar metasurfaces with continuously varying surface properties, this talk surveys the presenter’s works in departure to this trend. The first part of this talk examines the benefits to designing and implementing an aggressively discretized metasurface. This will be exemplified by metasurface designs of a near-grazing angle retroreflector and a perfect anomalous electromagnetic reflector. The latter part of this talk explores possibilities which avails us as we wrap a metasurface around a closed area. Simulations and experimental results will be presented which demonstrate the generation of an arbitrary waveform inside a metallic cavity. The talk will conclude with on implications and inspirations drawn from the aforementioned endeavors.
Short Bio:
Alex M. H. Wong is an Assistant Professor in applied electromagnetics, in the department of Electronic Engineering at the City University of Hong Kong. He is also a member of the State Key Laboratory of Millimeter Waves (partner Laboratory at City University of Hong Kong). He obtained his doctoral degree (Ph.D. 2014) in Electrical Engineering, then served briefly as a postdoctoral fellow at the University of Toronto in Toronto, Canada. He has advanced multiple projects on superoscillation-based imaging, “smart train” radar, and next-generation RF, infrared and optical metasurfaces. His current research is in the areas of metasurfaces, metamaterials and super-resolution systems. He has received several accolades which include an IEEE RWP King Award (for the best annual publication by a young author in the IEEE Transactions on Antennas and Propagation), an URSI Young Scientist Award, a Raj Mittra Grant, IEEE doctoral research awards from the AP and MTT societies and the national NSERC Canada Graduate Scholarship. He is a member of the IEEE (AP and MTT Societies).
