Light depolarization induced by metallic tips in apertureless near-field optical microscopy and tip-enhanced raman spectroscopy

Pietro Giuseppe Gucciardi (1) , Manuel Lopes (2) , Régis Deturche (2) , C. Julien , Dominique Barchiesi (3, 4) , Marc Lamy de La Chapelle (5, 2)

1 IPCF - CNR Istituto per i Processi Chimico-Fisici
2 LNIO - Laboratoire de Nanotechnologie et d'Instrumentation Optique
3 Gamma3 - Automatic mesh generation and advanced methods
4 UTT - Université de Technologie de Troyes
5 CSPBAT - Chimie, Structures et Propriétés de Biomatériaux et d'Agents Thérapeutiques

We have investigated the depolarization effects of light scattered by sharp tips used for apertureless near-field optical microscopy. Dielectric and metal coated tips have been investigated and depolarization factors between 5 and 30% have been measured, changing as a function of the incident light polarization and of the tip shape. The experimental results are in good agreement with theoretical calculations performed by the finite element method, giving a near-field depolarization factor close to 10%. The effect of depolarization has been investigated in polarized tip-enhanced Raman spectroscopy (TERS) experiments; the depolarization gives rise to forbidden Raman modes in Si crystals.

Mots clés: RESOLUTION; PROBE; POLARIZATION; SCATTERING; SI

Domaines: Optique / photonique

Pietro Giuseppe Gucciardi, Manuel Lopes, Régis Deturche, C. Julien, Dominique Barchiesi, et al.. Light depolarization induced by metallic tips in apertureless near-field optical microscopy and tip-enhanced raman spectroscopy. Nanotechnology, 2008, 19 (21), 215702 (7p.). ⟨10.1088/0957-4484/19/21/215702⟩. ⟨hal-00416084⟩