We demonstrate that patches of two dimensional arrays of circular plasmonic nanoholes patterned on gold-titanium thin film enables subwavelength focusing of visible light in far field region. Efficient coupling of the light with the excited surface plasmon at metal dielectric interface results in strong light transmission. As a result, surface plasmon plays an important role in the far field focusing behavior of the nanohole-aperture patches device. Furthermore, the focal length of the focused beam was found to be predominantly dependent on the overall size of the patch, which is in good agreement with that calculated by Rayleigh-Sommerfield integral formula. The focused light beam can be utilized to separate bio-particles in the dynamic range from 0.1 μm to 1 μm through mainly overcoming the drag force induced by fluid flow. In our proposed model, focused light generated by our plasmonic lenses will push the larger bio-particles in size back to the source of fluid flow and allow the smaller particles to move towards the central aperture of the patch. Such a new kind of plasmonic lenses open up possibility of sorting bacterium-like particles with plasmonic nanolenses, and also represent a promising tool in the field of virology.
Xiangchao Zhu and Ahmet A. Yanik, "Nanoplasmonic lenses for bacteria sorting (Presentation Recording)," Proc. SPIE 9550, Biosensing and Nanomedicine VIII, 95500L (Presented at SPIE Nanoscience + Engineering: August 10, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2189027.4519370515001.
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