报告题目：Spin-orbit interactions in optics and acoustics
报 告 人：Prof. Shubo Wang（City University of Hong Kong）
腾讯会议ID: 349 592 526
Spin and orbital angular momentum (OAM) are intrinsic properties of classical waves. Spin is associated with circular polarization (vector degrees of freedom) and is characterized by the local rotation of a vector field. OAM originates from the spatial phase gradient (scalar degree of freedom) and manifests as a helical wave front. The interplay between spin and OAM, referred to as spin-orbit interactions (SOIs), can give rise to intriguing wave phenomena such as spin-momentum locking and spin-Hall effect. In this talk, I will introduce our studies about SOIs in optical and acoustic systems in recent years. I will show that the optical SOI associated with Mie resonators coupled with a waveguide can give rise to a lateral optical force that can sort chiral particles , non-Hermitian exceptional point of arbitrary order [2, 3], and subwavelength optical isolation . Although sound can have novel properties deriving from the OAM , it is counterintuitive that SOIs can exist for sound, which is a longitudinal wave that carries no intrinsic spin. We found that airborne sound can possess artificial transversality in an acoustic micropolar metamaterial and thus behaves as a transverse vector wave with totally 6 degrees of freedom . Consequently, this transverse sound carries spin-1 and allows the realization of acoustic SOIs in both momentum space and real space. We achieved “acoustic activity” and leveraged it for chirality-dependent negative refraction and spin-dependent acoustic vortex generation by a dipole scatterer, both of which were realized for the first time in sound.
Dr Shubo Wang obtained B.S. degree from Shandong University in 2009 and Ph.D. degree from the Hong Kong University of Science and Technology (HKUST) in 2013. During 2013-2017, he worked as a Visiting Scholar in the Department of Physics and Institute for Advanced Study at HKUST. He joined the Department of Physics at City University of Hong Kong in 2017 as an Assistant Professor. Dr Wang’s research mainly focuses on the novel properties of classical waves and their interactions with matter. His recent interests include chiral light-matter interactions, non-Hermitian physics, angular momentum, and singular optics. He has published more than 30 papers in peer reviewed journals including Nature Communications, Science Advances, Physical Review Letters, and Physical Review X, among which some are selected as "Editors' Suggestion" and highlighted as "News and Views" in Nature Photonics. He has delivered 12 invited talks and 2 keynote talks at international conferences. Dr Wang received 4 grants from the Research Grants Council of Hong Kong SAR and is the recipient of William Mong Outstanding Paper Award. He serves as a Topic Editor for Photonics (IF 2.14) and a reviewer for a number of high-profile journals.