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Perfect transfer of waves
7 October 2022 @ 16:00 - 17:00
Q-Han Park
Korea University
Waves, both classical and quantum, are reflected when they encounter different media or potential regions. Reflection is a fundamental property of waves underlying numerous scientific applications. Nevertheless, in many cases removing reflection is a key issue to secure transmission and increase device efficiencies. Since the early works of Brewster and Rayleigh, much effort has been made to remove reflection, or achieve so called anti-reflection (AR). The most well-known AR coating, based on a simple interference principle of optics, only works for specific frequencies and incidence angles. Despite efforts to extend AR to broader frequency, progress was achieved mainly by the trial-and-error optimization in designing multilayer AR structures. So far, AR has been regarded as a technological issue without much room for further fundamental understanding.
Here, we uncover a principle of universal impedance matching (UIM) that allows a complete removal of reflection regardless of the incidence angle and the frequency of incoming waves. In the case of electromagnetic waves, we reformulate the Maxwell’s equation in terms of impedance and admittance functions and directly establish the inverse scattering relation between scattered fields and material parameters, i.e., permittivity and permeability. Particularly, from the inverse scattering relation we find that the perfectly vanishing reflection, omnidirectional and frequency independent, can be explicitly realized by spatiotemporally dispersive materials. As a demonstration, we introduce an UIM coating that enables the perfect transmission of white light in heterogeneous transparent media. We also present an experimental realization of UIM using metamaterials.
The complete removal of reflection based on UIM can be extended to various physical situations, such as light reflection at curved surface interfaces, reflection at the junction two different waveguides, total internal reflections, reflection of acoustic and elastic waves and reflection of quantum matter waves at potential steps. We explain how UIM can be extended to these physical systems and applied to practical devices.
About Speaker
Dr. Q-Han Park is currently Professor in Physics at Korea University in South Korea. He received his Ph.D. degree in Physics from Brandeis University, United States in 1987. He was a Postdoctoral Research Fellow at University of Cambridge with Stephen Hawking from 1990 to 1992. Afterwards he was a research associate at CERN, Switzerland, a visiting scholar at MIT, United States, and a senior visiting fellow at the Institute of Optics, United States. He then joined Kyunghee University in South Korea as Assistant Professor in 1992, and moved to Korea University in 2001.
Dr. Park served as a director of Research Institute Basic Sciences in Korea, and an associated editor for Optics Express of the Optical Society of America. Dr. Park is currently Fellow of the Korean Academy of Science and Technology, American Optical Society, Optical Society of Korea, and Korean Physical Society. He is also serving as Director of the Center for Electromagnetic Metamaterials of Korea University and Consultant of Samsung Advanced Institute of Technology. He has received the prestigious Korean Science Award by the Ministry of Science and ICT in 2020.
Dr. Park’s research has been focused on high energy physics until the year of 2000 and switched to the field of optics. Since then, he published high impact papers on optics including five papers in Nature Photonics and holds 35 patents. In earlier works, he made significant theoretical advances in Plasmonics. His recent research topics include universal impedance matching and non-local metamaterials. He has authored more than 200 journal articles and 47 patents. More details can be found on his homepage (http://nol.korea.ac.kr/).
Topic: Nanocolloquium Series
Time: Oct 7, 2022 04:00 PM Istanbul
Join Zoom Meeting
https://zoom.us/j/5876884794?pwd=OUNFRTZKZDNRMm5MWjJjSlhnMXFNUT09
Meeting ID: 587 688 4794
Passcode: 871377
