Abstract
Various transformational devices and effects based on inhomogeneous metamaterials have been proposed, such as invisibility cloaks, photonic black holes, etc. Different approaches are invented to realize transformation optics. Recently, the speaker and his research group apply inhomogenous waveguide to transformation optical effects, such as mimicking gravitational lensing and bending light beam. In this talk, the speaker proposes an enhanced photothermal effect facilitated by a Fabry-Perot (FP) cavity to achieve light-controllable transformation optics devices. A planar silver/PMMA/silver FP cavity is fabricated. In the experiment, a Gaussian pump laser beam is incident normally on the cavity and induces a change in the refractive index of PMMA layer due to thermal heating. A probe laser beam with wavelength of 457nm is coupled into the silver/PMMA/silver waveguide through a grating. The structure can be seen as a transformation optical lens. The refractive index is spatially continuously changed and the light beam is bending continuously at different locations. As the refractive index is non-uniform, the bending angle of light beam will be quite different for different input light beam. Here, the distance between the light beam and the center of lens can be defined as impact parameter distance r_0. In the experiment, light beam is continuously moved from a distance to the center of lens through changing the location of laser spot of 457nm laser on the grating. The results show, for different r_0, different trajectory of light beam can be obtained around the transformation lens. This work reported a flexible method to fabrication transformation optical media. The refractive index of the polymer inside the cavity is inhomogeneously changed. This is used to change the trajectory of light beam inside the polymer layer. Such a method can be extended to fabricate many other transformation optical medium. All such potential expansibility of this system provide new ways to develop various multifunctional transformation devices in the future.
About the speaker
Prof Hui Liu received his PhD in Physics from Nanjing University in 2003. In 2004 to 2005, he did postdoctoral research at University of California at Berkeley. He joined Nanjing University in 2006 and is currently Professor of Physics. He is also the Associate Director of the National Key Laboratory of Solid State Microstructures. In 2014, Prof Liu was awarded the Outstanding Young Talents of China by the National Science Foundation. His research interest includes solid-state laser of optical superlattices, quantum optics in metamaterials, and curved space-time in photonic chips. He has published over 60 Science Citation Index (SCI) papers, including Nature Photonics, Physical Review Letters, etc. He has taken charge of several national projects, including "863" key projects and National Natural Science Foundation of China (NSFC) projects. He also worked as the referee for Optics Express, Journal of the Optical Society of America B (JOSAB).
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