Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Plasmonics and Nanooptics III

O 28.5: Talk

Tuesday, March 15, 2011, 12:15–12:30, WIL A317

Enhanced vibrational near-field spectroscopy of PMMA with infrared antennas — •Jón Mattis Hoffmann, Jens Richter, and Thomas Taubner — I. Institute of Physics (IA), RWTH Aachen University, Sommerfeldstraße 14, 52074 Aachen, Germany

Infrared spectroscopy allows for the investigation of chemical properties of a sample material by directly probing molecular vibrations. Combined with scattering-type near-field optical microscopy (s-SNOM), which relies on the scattering of light at a sharp metallic tip, it is possible to obtain such spectroscopic information in images with strongly subwavelength resolution [1]. For the probing of weakly absorbing samples, such as molecular vibrations in thin polymer layers [2], increased sensitivity of infrared near-field spectroscopy is needed. It has been shown that signals in near-field vibrational spectroscopy of thin films can be enhanced by reflecting substrates [3]. For even higher enhancement factors we investigate the possibility of using resonant substrates.

Here we employ triangular nanostructures fabricated by nanosphere lithography that exhibit strong resonances in the infrared region as substrate. We want to measure the resonant enhanced near-field spectra of a thin PMMA film on top of these infrared antennas.

[1] F. Keilmann et al. in Nano-Optics and Near-Field Optical Microscopy ed. by A. Zayats and D. Richards, 235 (ArtechHouse, 2009).

[2] T. Taubner et al., Applied Physics Letters 85, 5064 (2004).

[3] J. Aizpurua et al., Optics Express 16, 1529 (2008).