Departmental Seminar

Multipole plasmonic metasurfaces & functional thin-film optical coatings

Dr Jihua Zhang

Metasurfaces are two-dimensional nanoantenna arrays that can control the amplitude, phase, and polarization of light with subwavelength resolution. However, the technological relevance of the original ultrathin metasurfaces is questionable due to their limited efficiency in manipulating the transmitted light. Huygens and multipole schemes have been proposed to successfully tackle this efficiency issue in dielectric metasurfaces. However, the efficiency of plasmonic metasurfaces remains low, with a state of the art of only 10% in the visible and near-infrared region. In this seminar, a multipole plasmonic metasurface will be presented to decrease the absorption loss and increase the transmission efficiency. High transmission efficiency over 90% and polarization conversion efficiency over 40% are demonstrated in the visible and near-infrared region. The technological relevance of the multipole plasmonic metasurface will be highlighted by demonstrating applications in simultaneous anti-reflection and anti-transmission, beam deflection, hologram, and 3D imaging.

Although metasurfaces have great a potential in light control, they typically require advanced and costly lithography for fabricating subwavelength nanostructures, and thus make them of minor practical relevance for low-cost large-scale applications. Alternatively, thin-film optical coatings supporting interference resonance provide a lithography-free and highly scalable solution in manipulating the amplitude, phase, and polarization of light. In the second part of this seminar, thin-film optical coatings will be introduced and utilized to realize functions in perfect absorption, Fano resonance, mathematical operation, wavefront and polarization controls.

Jihua Zhang is a postdoctoral fellow in Nonlinear Physics Centre of Australian National University since January 2020. He obtained BS degree from Huazhong University of Science and Technology in 2011, and dual PhD degrees from University of Paris-Saclay and Huazhong University of Science and Technology in 2016. His PhD research was focused on nonlinear integrated photonics. After that, he worked as a postdoctoral associate in the Institute of Optics at University of Rochester for three years, where his research was in metasurfaces, thin-film nanophotonics, and femtosecond laser nanofabrication.

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