Abstract: 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.

Bio: Hou-Tong Chen received B.S. and M.S. degrees from the University of Science and Technology of China and a Ph.D. from Rensselaer Polytechnic Institute . all in physics. He is currently a technical staff member in the Center for Integrated Nanotechnologies at Los Alamos National Laboratory. His research interests include metamaterials and metasurfaces, terahertz science and technology, ultrafast nanophotonics, and near-field microscopy.