讲座时间：11月27日9:30

讲座地点：科C218

讲座题目：The Self-Consistent Theoretical Model and Numerical Method for Incorporating the Gain into Dispersive Nanostructures

主讲人：沙威

报告简介：Photon exhibits wave-particle duality, and thus could transfer its momenta to an object when electromagnetic (EM) waves are reflected or absorbed. Moreover, EM waves also could carry spin angular momentum (SAM) with a circular polarization and orbital angular momentum (OAM) with a helical or twisted wavefront. Both SAM and OAM produce torque to rotate the object.  In this presentation, I will review our recent works on angular momenta of EM waves at microwave frequencies.

First, theoretical foundation is introduced for the SAM and OAM of EM waves. I will show how to derive the linear momentum by the de Broglie hypothesis. Then, the linear momentum will convert to the radiation momentum at the sourceless region. Finally, the radiation angular momentum will split into the SAM and OAM. Here, the similarities between angular momenta of electrons and those of photons will be discussed.

Second, omega-shaped chiral metamaterials are explored to generate circularly polarized waves carrying SAM. The chiral metamaterials have two aligned electric and magnetic dipole pairs, and thus show flexible capability to tune the polarization states of EM waves.

Third, the Berry-phase inspired metasurfaces are employed to convert plane waves carrying non-zero SAM and zero OAM to the vortex beams carrying the reversed SAM and arbitrary-order OAM. For reflective metasurfaces, the high conversion efficiency can be achieved by a perfect electric conductor-perfect magnetic conductor anisotropic surface. For transmittivemetasurfaces, the high conversion efficiency can be gained by a Babinet-inverted bi-layered structure.

Title: Spin and Orbital Angular Momenta of Electromagnetic Waves: A Preliminary Study

主讲人简介：沙威，男，生于1982 年4 月。2003 年7 月与2008 年6 月毕业于安徽大学，分别获电子信息工程专业工学学士和电磁场与微波专业工学博士学位。2008年7 月至2012 年5 月，在香港大学电机电子工程系从事博士后研究工作；2012年6 月至2017 年7 月任该系的研究助理教授、博士生导师。2017 年，入选第十三批国家“”青年项目，并同时获欧盟“地平线-2020”研究与创新框架下的“玛丽居里学者计划”资助。2017 年10 月至今，任职于浙江大学信息与电子工程学院，特聘研究员、博士生导师。

沙威博士已合作撰写了2 本专著和4 章专书。他已发表SCI 检索论文90 篇，并贡献18 个国际会议邀请报告。Google Scholar 引用3300 多次，h-index 指数26。沙威博士是美国电气电子工程师学会高级会员和美国光学学会会员。他在本领域国际会议EDAPS, ACES, ICCEM, PIERS, IMWS-AMP 等也兼任分会主席、程序委员会委员、评奖或评审委员会委员、客座编辑等职位。2014年被评为Journal of Computational Physics 期刊的Outstanding Reviewer。他在2007 年获中国青少年科技创新奖，2013 年获香港大学研究成果奖，2015 年获安徽省科学技术奖二等奖。他指导的博士生在国际会议上获4 次最佳学生论文奖，1 次青年科学家奖。他当前的研究领域包括电磁学、纳米光子学、非线性及量子光学、光电子学、及多物理场分析。