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O: Fachverband Oberflächenphysik

O 28: Plasmonics and Nanooptics III

O 28.4: Vortrag

Dienstag, 15. März 2011, 12:00–12:15, WIL A317

Nonlocal, grating-coupled scattering-type near-field scanning optical microscopy of individual gold nano-particles — •Diyar Sadiq¹, Javid Shirdel¹, Jae Sung Lee², Namkyoo Park², and Christoph Lienau¹ — ¹Institut für Physik, Carl von Ossietzky Universität, 26111 Oldenburg, Germany — ²Photonic Systems Laboratory, School of EECS, Seoul

Scattering-type near-field scanning optical microscopy (s-NSOM) is now routinely used for (sub-) 10-nm-resolution optical imaging of surfaces. The performance is, however, often limited by a rather substantial signal background resulting from a direct optical illumination of the scattering antenna. Various ideas for a nonlocal optical excitation have therefore been proposed, e.g., by grating-coupling of surface plasmon polaritons (SPP) onto adiabatic metallic tapers and three-dimensional focusing of SPP wavepackets towards the tip apex [1]. Recently, first line-scan images recorded by using such probes demonstrated 20 nm resolution and coupling of about 15% of the SPP intensity onto the tip apex [2]. Here, we use such a grating-coupled SPP microscope for the first time for s-NSOM imaging of single metallic nano-particles. We demonstrate sub-20-nm-resolution imaging of localized SPP fields and observe that more than 40% of the grating-coupled SPP field is localized at the taper apex. The results are supported with numerical simulation based on the finite-difference time-domain (FDTD) method. [1] C. Ropers et al. Nano Letters 7, 2784 (2007). [2] C. C. Neacsu et al, Nano Letters 10, 592 (2010).