12 May 2009 Dielectric-metal-dielectric nanotip for SNOM
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Abstract
Superfocusing of light, far better than the diffraction limit, is of crucial importance for scanning near-field optical microscopy (SNOM), optical chemical sensing, and nanolithography. For SNOM applications there are two typical geometries. The first are tapered-fiber metal-coated aperture probes, which are being constantly improved. The other are tapered metal or metal-coated apertureless tips, which are continuously brought to perfection. We propose a modification of a metal-coated fiber tip, which has an additional, thin, dielectric coating with refractive index greater than that of air, what leads to higher field enhancement at the tip. The excitation signal is an internal, radially polarized Laguerre-Gauss beam. There is no sound theoretical model to describe nanofocusing of plasmons and we limit the scope of investigations to body-of-revolution finite-difference time-domain (BOR FDTD) simulations using in-house code. We find that with an increase of the refractive index of nanocladdings the maximum enhancement occurs for increasingly longer wavelengths.
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Tomasz J. Antosiewicz, Tomasz J. Antosiewicz, Piotr Wróbel, Piotr Wróbel, Tomasz Szoplik, Tomasz Szoplik, } "Dielectric-metal-dielectric nanotip for SNOM", Proc. SPIE 7353, Metamaterials IV, 73530I (12 May 2009); doi: 10.1117/12.827499; https://doi.org/10.1117/12.827499
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