UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2005 Meeting


Section: Polymer Physics


Title:
Apertureless scanning near-field microscopy


Authors:
C.C. Neacsu, M. B. Raschke


Affiliation:
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Berlin, Germany


E-mail
neacsu@mbi-berlin.de, raschke@mbi-berlin.de


Keywords:


Abstract:
The optical antenna properties of metallic tips to detect and concentrate light to highly confined regions is being investigated and employed for ultrahigh resolution near-field microscopy: In linear light scattering the plasmonic characteristics of the emission behavior of individual nanoscopic tips has been investigated and allowed for an understanding of the correlation of spectral dependence and local-field enhancement with structural parameter - providing important selection criteria for tips to be used as probes in scanning near-field microscopy [1]. In nonlinear light scattering, the unique symmetry properties of the tips (mm) allowed for the otherwise inseparable distinction between surface and bulk contributions in second-harmonic generation (SHG). The study also allowed to derive general symmetry selection rules for SHG from nanostructures [2]. The local-field confinement at the tip apex in combination with resonance Raman spectroscopy provide an optical scanning probe method with ultrahigh spatial resolution. Here, the coupling between the illuminated tip apex and the metallic substrate plane allows for a high degree of local-field enhancement, thus having the required sensitivity for nanoscale spectroscopy of molecular adsorbates. The temporal and spectral behavior of the Raman signal we observe is characteristic for probing only single emitters in terms of single molecules or small clusters [3]. [1] C.C. Neacsu, G.A. Steudle, M.B. Raschke, App. Phys. B 80, 295 (2005); [2] C.C. Neacsu, G.A. Reider, M.B. Raschke, Phys. Rev. B, (in press); [3] C.C. Neacsu, M.B. Raschke, (in preparation).