主讲人：陈磊（马里兰大学）

题目：WAVE SCATTERING PROPERTIES IN COMPLEX SCATTERING SYSTEMS:

ZEROS AND POLES OF SCATTERING MATRIX

时间：2021年06月11日上午09：00

会议ID:（腾讯会议）769 465 167

地点：理工楼1201

报告摘要：

Wave scattering properties in complex scattering systems have been of great interest to both the physics and engineering communities because of their useful characterizations of such systems and significant value for applications. The most common tool for studying such properties – the scattering (S)-matrix, can be fully represented by its zeros and poles in the complex energy/frequency plane. There has been substantial effort to understand the scattering properties and wave phenomena inside complex systems in the past, both theoretical and experimental, which in turn lead to significant advancement in many applications: wavefront shaping (WFS), coherent perfect absorption (CPA), wireless power transfer, electromagnetic interference (EMI), etc.

In this talk, I will summarize the recent progress and interest regarding an intriguing wave phenomenon – coherent perfect absorption (CPA) in the complex scattering systems. We have successfully implemented CPA protocols in generic complex scattering systems without any geometric or hidden symmetries [1], which greatly extends CPA beyond its initial concept as the time-reversal of a laser cavity. Under such efforts, we have also established a convenient approach for control of the local losses inside the network system, which helped us to uncover the mystery of matching the imaginary part of the S-matrix zero to the uniform loss of the system. We thus developed the theoretical representation of the S-matrix by its zeros and poles, and generalized the traditional Wigner time delay to a complex quantity in sub-unitary scattering systems [2].  We have revealed the inherent connection between the complex Wigner time delay and coherent perfect absorption, and can utilize the new complex Wigner time delay idea for extracting S-matrix zeros and poles in a practical system. The ultimate goal is to manipulate the zeros and poles of the S-matrix, by adding losses in the system or changing the coupling of the scattering channels, etc. Such a capability will be extremely useful for understanding the wave properties in the complex scattering systems, and for controlling the wave behavior in optics, electromagnetics, acoustics, quantum transport in condensed matter systems, etc.

References:

[1] Lei Chen, Tsampikos Kottos, and Steven M. Anlage, “Perfect Absorption in Complex Scattering Systems with or without Hidden Symmetries,” Nature Communications 11, 5826 (2020).

[2] Lei Chen, Steven M. Anlage, and Yan V. Fyodorov, “Generalization of Wigner Time Delay to Sub-Unitary Scattering Systems,” Phys. Rev. E 103, L050203 (2021).

个人简介：

Lei Chen (陈磊) is a PhD student in the Department of Electrical and Computer Engineering at University of Maryland, College Park (USA). Prior to starting the PhD study, he received his B.S. degree from Huazhong University of Science and Technology in 2016. He is now working as a graduate research assistant under the supervision of Prof. Steven Anlage (Physics & ECE). His research interests include wave/quantum chaos, quantum graphs and networks, and microwave technologies.