报告题目：From absorbers to lenses: designing highly-efficient metasurfaces
报告人：Mitchell Guy Kenney 博士
摘要：Metasurfaces, the 2D variant of metamaterials, have been at the forefront of optics research in the past decade, due to the simplicity and flexibility of their design, and the impact of novel devices which can be realised. Primarily designed using plasmonic effects – fabricated from patterned metallic nanostructures – metasurfaces suffered from poor performance when carrying out the desired response. This is due to the low interaction of light when transmitted through metallic thin films, where the efficiency is typically limited to ~15% or less. Here, I will talk about my work carried out during the last 5 years at both the University of Birmingham (Prof. Shuang Zhang) and, more recently, at the University of Glasgow (Prof. David Cumming), on developing metasurfaces which exhibit very high performance utilising reflection or transmission operation. As examples, I will talk about the following projects; firstly, visible-IR holograms, which were realised using spatially-oriented gold nanorods atop a groundplane (reflectarrays), were able to reach 80% efficiency (Nature Nano, 2015). Secondly, by utilising silicon herringbone structures and geometric phase, asymmetric transmission of circularly polarised THz light was achieved, with conversion efficiencies exceeding 60% (Adv. Mater, 2016). Thirdly, whilst working towards the “SuperCamera” (triple wavelength) project at UoG, I designed ultra-broadband THz absorbers of one octave bandwidth and an average absorption of 86% using supercells of fractal antennas (ACS Photon, 2017). Finally, my current work lies with the production of large aperture dielectric metalenses (1 mm and 10 mm) operating in the near Infrared, with a range of f-numbers and reaching focusing efficiencies of 60% (in progress). Metasurfaces are now at a standard of interest to commercial prospects and show real promise for being a highly sought after commodity in the future.
报告人简介：Dr. Mitchell Guy Kenney received his Ph.D. degree in Physics from University of Birmingham in 2016. He has been working as a research associate in School of Engineering in University of Glasgow since 2015.His main research interests include metasurface, plasmonics and CMOS image sensors. He has published 11 journal publications, including Nature Nanotechnology, Advanced Materials, ACS Photonics, etc.