Events

Seminar with Dr. Margoth Cordova Castro

Wednesday, July 10, 2019, 11:00 HPP M 12 -  Hoenggerberg

 

** Speaker: Dr. Margoth Cordova-Castro, Kings College London

** Title: Hyperbolic Plasmonic Materials

** Abstract: Hyperbolic materials are anisotropic media which exhibit metallic or dielectric behaviour depending on polarisation. Natural hyperbolic materials as well as hyperbolic metamaterials, composites with engineered optical properties that opened up new avenues for light manipulation, have an unprecedented ability to concentrate light on deeply subwavelength scales which promises a wide variety of new applications in nanophotonic technologies. I developed three new material platforms for the realisation and control of hyperbolic dispersion and describes their optical properties. These include a metamaterial based on an array of plasmonic nanocones, heterostructured metamaterial based on Au-ZnO-Au meta-atoms and a natural hyperbolic material CuS. A combined experimental and theoretical study of the optical properties of CuS colloidal nanocrystals show that they exhibit anisotropic plasmonic behaviour in the infrared and support optical modes with hyperbolic dispersion in the visible spectral range. Heterostructured, layered Au-ZnO-Au nanorod metamaterials supporting guided modes were developed with the introduction of a nanoscale dielectric gap in the meta-atoms. The role of the shape of meta-atoms forming the array has been studied on the example of transformation of nanorods forming the metamaterial into nanocones. The plasmonic mode structure of the individual nanocones and pronounced coupling effects between them provide multiple degrees of freedom to engineer both the field enhancement and the optical properties of the metamaterials. These metamaterials are the first so-called gradient refractive index metamaterials that behave as a medium with elliptic optical dispersion in the region of the nanocone apexes and hyperbolic optical dispersion in the region of the bases. A scalable manufacturing process for these metamaterials allowing mass-production at the centimeter scales has been proposed and developed. The introduced natural and engineered plasmonic hyperbolic materials bring about new opportunities for future exploration and applications of these unusual systems in nanophotonics for linear and nonlinear light manipulation, fluorescence control, surface enhanced Raman spectroscopy as well as hot-carrier plasmonics and photocatalysis.

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