Two-dimensional plasmonic metamaterials – metasurfaces – offer tremendous opportunities in realizing exotic optical properties and functionalities. Through tailoring the resonant response of basic building blocks as well as their mutual interactions, they enable effective control of the amplitude, phase, and polarization state of optical reflection, transmission, and scattering. In this talk, I will present plasmonic metasurfaces consisting of a few planar layers of subwavelength metallic structures, demonstrating optical functionalities such as antireflection and perfect absorption. By judicious design of anisotropic resonances, the off-resonance phase dispersion can be tailored to achieve achromatic phase retardation, through which we demonstrate ultrabroadband linear polarization rotation and linear-to-circular polarization conversion (i.e., achromatic half and quarter waveplates). In the second topic, I will present hybrid metasurfaces by integrating functional materials such as semiconductors and graphene at critical regions of the resonators, allowing enhanced light-matter interactions and accomplishing dynamic switching, active tuning, and enhanced nonlinearity. In particular, I will show hybrid graphene metasurfaces for efficient optical modulation at mid-infrared wavelengths for imaging applications. The augmented metasurface functionalities through both structural design and materials integration will provide promising opportunities of metasurfaces for real-world applications.
Hou-Tong Chen received BS and MS degrees from University of Science and Technology of China in 1997 and 2000, and a Ph.D. degree from Rensselaer Polytechnic Institute in 2004, all in physics. He is currently a Technical Staff Member in the Center for Integrated Nanotechnologies, Los Alamos National Laboratory. His research interests include metamaterials and metasurfaces, terahertz science and technology, ultrafast nanophotonics, and near-field microscopy. He has published over 70 journal papers and delivered nearly 100 invited technical presentations in conferences and accredited research institutions. He is a Topical Editor of Optics Letters (since 2017), and the conference chair of the 8th Optical Terahertz Science and Technology (OTST 2019) to be held at Santa Fe, USA (2019). He won LANL Fellows’ Prize for Outstanding Research (2015), and is a Fellow of American Physical Society (2015).