Light-field Enhancement at the Nanoscale for Sensing

Prof. Saulius Juodkazis

Centre for Micro-Photonics, Swinburne University of Technology

3:30 pm Friday, 20 September 2013, EN313 (EN Building), Hawthorn.

Light field enhancement by metallic nanoparticles and nano-textured surfaces is currently in the focus of research for light harvesting applications and sensing. Surface enhanced Raman scattering (SERS) on surfaces produced by laser ablation, plasma etching, and lithographically defined nano-particles can deliver sensitivity levels required to detect sub-nano-molar concentrations of analytes in liquid and in air.  Sensitivity of SERS detection is related to the actual surface area, morphology of plasmonic metal coating, its thickness, steric matching and hindrance on a molecular level. These effects have to be better understood for practical use of nano-textured surfaces and nano-particle arrays for sensing. 
Plasmonic nanoparticles of a well-defined geometry fabricated by electron and ion beam lithography provide a possibility to test achievable light enhancement limits in SERS. The 1 to 10-nm-wide nano-gaps deliver strongest light nano-focusing. Recent results of nano-gap fabrication with shape and size control of nano-gaps milled by focused ion beam will be discussed.  Alternatively to the top-down approach, large areas of nano-textured surfaces can be made by plasma etching and laser ablation and provide a more practical solution for SERS applications.

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