◈ Special Issue Information：

This Special Issue aims to invite researchers to contribute original research papers, dealing with all aspects of topological classical waves. Topics of interest include, but are not limited to:

• EM/acoustic metamaterials with topological frequency band
• Vortex beams
  
• Bound state in continuum (BIC)
  
• Topological EM / acoustics devices
  
• The interaction between band topology and non-hermicity / nonlinearity

◈ Special Issue Editors：

	Fei Gao Professor Zhejiang University, China
	Baile Zhang Professor Nanyang Technological University, Singapore

◈ Manuscipts Submission:

Manuscripts should be submitted online. This special issue title should be selected during the online submission process. All papers will be peer-reviewed. Accepted papers will be published online continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers).

◈ Published Papers in This Special Issue:

2020-11-26 Designer Surface Plasmons Enable Terahertz Cherenkov Radiation (Invited) By Jie Zhang, Xiaofeng Hu, Hongsheng Chen, and Fei Gao Progress In Electromagnetics Research, Vol. 169, 25-32, 2020 doi:10.2528/PIER20102708
2020-12-02 One-Way Topological States Along Vague Boundaries in Synthetic Frequency Dimensions Including Group Velocity Dispersion (Invited) By Qingrou Shan, Danying Yu, Guangzhen Li, Luqi Yuan, and Xianfeng Chen Progress In Electromagnetics Research, Vol. 169, 33-43, 2020 doi:10.2528/PIER20083101
2021-12-20 Tunable Topological Refractions in Valley Sonic Crystals with Triple Valley Hall Phase Transitions (Invited) By Ding Jia, Yin Wang, Yong Ge, Shou-Qi Yuan, and Hong-Xiang Sun Progress In Electromagnetics Research, Vol. 172, 13-22, 2021 doi:10.2528/PIER21102002
2021-12-24 Non-Hermitian Skin Effect and Delocalized Edge States in Photonic Crystals with Anomalous Parity-Time Symmetry By Qinghui Yan, Hongsheng Chen, and Yihao Yang Progress In Electromagnetics Research, Vol. 172, 33-40, 2021 doi:10.2528/PIER21111602

More papers to be added here ...