Antennas Guest Speaker Seminar: Transformation optics with field transformation for additional polarization and impedance control
Presenter Dr. Jensen Li, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
Transformation optics is mainly enabled by metamaterials with varying indices and anisotropies in both the dielectric permittivity and magnetic permeability tensors. Being inspired by the parallel development for homogeneous metamaterials that artificial atoms with lower symmetries or with magneto-electric coupling to provide exotic optical properties such as huge optical activity, electromagnetic-induced transparency and asymmetric transmission, etc., the ability of transformation optics is far from being fully utilized by only covering a limited palette of optical responses. In this talk, we investigate two dimensional transformation optical devices enabled by a scheme called field transformation [Phys. Rev. Lett. 111, 033901 (2013)]. Instead of coordinate transformation, the scheme is driven by transforming the field amplitudes. It requires anisotropic materials with non-trivial principal axes or bianisotropic materials in the most general context. The scheme gives us additional degrees of freedom in controlling polarization and impedance, complementary to the conventional approach, which is usually used for controlling the size and shape of an object. For example, we can design a device to achieve complete cross-polarization conversion between TE and TM polarizations. We can mimic a perfect magnetic conductor of arbitrary shape. We can also obtain additional impedance control when a transformation optical device is matched to an object. In this talk, we will also discuss the transformation of an optical beam using a recent approach of metasurfaces.
Dr Jensen Li has just been appointed as a senior lecturer at the University of Birmingham. He received his PhD in 2004 from Hong Kong University of Science and Technology. Afterwards, he spent two years in the Imperial College London with a postdoctoral fellowship from the Croucher Foundation and two years in University of California, Berkeley. Prior to his joining University of Birmingham, he was an assistant professor at the City University of Hong Kong. He and his research group have been active in metamaterials and transformation optics research. He has authored 2 book chapters and more than 40 research articles in journals including Nature Materials, Physical Review Letters, and Advanced Materials.
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