Engineering hotspots is of crucial importance in many applications including energy harvesting, nano-lasers, subwavelength imaging, and biomedical sensing. Surface-enhanced Raman scattering spectroscopy is a key technique to identify analytes that would otherwise be difficult to diagnose. In standard systems, hotspots are realised with nanostructures made by acute tips or narrow gaps. Owing to the low probability for molecules to reach such tiny active regions, high sensitivity is always accompanied by a large preparation time for analyte accumulation which hinders the time response. Inspired by transformation optics, we introduce an approach based on warped spaces to manipulate hotspots, resulting in broadband enhancements in both the magnitude and volume. Experiments for single molecule detection with a fast soaking time are realised in conjunction with broadband response and uniformity. Such engineering could provide a new design platform for a rich manifold of devices, which can benefit from broadband and huge field enhancements.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2016-CRG5-2995
Acknowledgements: The work is supported by H2020 European Research Council Project Nos. 734578 (D-SPA) and 648783 (TOPOLOGICAL), Leverhulme Trust (Grant no. RPG-2012-674), the Royal Society, the Wolfson Foundation, the Engineering and Physical Sciences Research Council (EP/J018473/1), National Natural Science Foundation of China (Grant no. 11604161), the Jiangsu Provincial Natural Science Foundation (Grant no. BK20160914), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant no. 16KJB140009),Natural Science Foundation of Nanjing University of Posts and Telecommunications (Grant no. NY216012), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant (Grant no. 752102), and the funding from KAUST (Award OSR-2016-CRG5-2995).