Symposium 20 years of nano-optics April 6th, 2004 Auditorium, Institute of Physics, St.Johanns-Ring 25

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2 Symposium 20 years of nano-optics April 6th, 2004 Auditorium, Institute of Physics, St.Johanns-Ring 25 9:30 9:45 Coffee and Gipfeli 9:45 10:00 Welcome address and introduction B. Hecht Uni Basel H.-J. Güntherodt Director NCCR Near-field microscopy: A personal view Dr. U. Fischer Institute of Physics, University of Münster, Germany Not so near-field: imaging deep in living scattering tissue. And: 3D nearfield? Dr. W. Denk Max-Plank Institute for Medical Research, Biomedical Optics, Heidelberg, Germany :00 Break 13:00 13:45 Near-field effect and nonlinear effect for nanoscale molecular imaging and spectroscopy Prof. Dr. S. Kawata Osaka University and RIKEN, Japan 14:00 14:45 Probing the structure and the dynamics of single molecules adsorbed on silver nano-particles by surface enhanced Raman spectroscopy Prof. Dr. A.J. Meixner University of Siegen, Germany 15:00 15:15 Coffee break 15:15 16:00 Surface waves in the near field: a new perspective Prof. Dr. J.-J. Greffet Ecole Centrale Paris, France 16:15 17:00 Optics on the nanometer scale Prof. Dr. L. Novotny Institute of Optics, University of Rochester, USA 17:15 - Apero

3 Breaks and Apero take place in the entrance hall St. Johanns-Ring 25. The lectures take place in the great lecture hall St. Johanns-Ring 25. Directions to the Physics Institute of the University of Basel St. Johanns-Ring Klingelbergstrasse Pestalozzistrasse Biozentrum

4 Abstracts: U. Fischer Uni Münster, Germany Near-Field Optics - a personal view My involvement with near field optics began with experiments to demonstrate the concept of contact imaging by energy transfer as proposed in the sixties by Hans Kuhn. There, the near field interaction of excited dye molecules in a monolayer with a a planar metal nanostructure is used to form a copy of the metal structure as a pattern of fluorescent dye molecules at a resolution which is limited by the distance between the metal pattern and the monolayer. During these experiments it turned out, that the metal nanostructures when illuminated with light show similar near field phenomena as the molecules and we started with experiments to use apertures and later metal protrusions in a planar metal film as submicroscopic sources for near field microscopy. The approach of Pohl et al. using apertures on a tip compatible with SPM techniques was better suited for near field microscopy and lead to remarkable results of near field microscopy triggered by the work of Betzigs group: Single moelcule imaging by Betzigs group and mapping of exciton wave functions of quantum dots by Saikis group. The application of near field microscopy to biological objects in liquid environment is still a difficult task which was recently demonstrated by the work of Nabers group. Important new optical information has thus been obtained with near field microscopes at a resolution of nm. Image formation in a near field microscope is a complex process. A near field source induces a polarisation in the object. The coherent superposition of the radiation of the source and of the sample leads to the signal for imaging. The difficult part is the conversion of the near field distribution to the radiated signal. In the case of incoherent spectroscopic imaging such as fluorescence SNOM the imaging process is easier to understand. The fluorophores can be considered more or less as reporters of the intensity of the near field. Several challenges of near field optics remain. Imaging at a resolution beyond 10 nm. I think there is a chance for molecular samples on a metall substrate. Furthermore the link of the radiation field to nanoscopic light sources remains an interesting physical question related to the generation of nanoscopic light sources of high intensity which are highly relevant not only for the development of near field optical data storage.

5 W. Denk MPI Heidelberg, Germany Not so near-field: imaging deep in living scattering tissue. And: 3D nearfield? High resolution optical microscopy or living tissue is crucial to many areas of Biology. A particular challenge is highly interconnected neural tissue, which in addition is highly scattering. Multi-photon optical microscopy allows deep penetration into intact brain tissue. Nanoscopic optical imaging in 3 dimensions has been a challenge. Maybe near-field imaging and slicing the sample is the answer.

6 13:00 13:45 S. Kawata Osaka University and RIKEN, Japan Near field effects and nonlinear effects for nano-scale molecular imaging and spectroscopy To achieve a nano imaging and nano manipulation with photons, interaction scale should be much smaller than the wavelength of light. This can be realized by exciting the local mode of surface plasmon polariton at a metallic nano particle, or by exciting nonlinear photon process with a femto/pico second laser pulse. In this presentation, I will review our research progress with our latest results where in addition to electromagnetic near-field enhancement you will find the near-field chemical spectral shift in Raman signal and mechanical force contribution of the probe to the spectrum. Results of near-field plus nonlinear NSOM will be also presented.

7 14:00 14:45 A.J. Meixner Uni Siegen, Germany Probing the structure and the dynamics of single molecules adsorbed on silver nano-particles by surface enhanced Raman (SER-) spectroscopy We report on spatially resolved SER-spectroscopy at the single-molecule level of various rhodamine dyes, of pyronine G and thiopyronine adsorbed on isolated silver nano-particles. While the electromagnetic or near-field contribution to the enhancement of the Raman signal caused by the metal nano-structure is quite well understood nowadays, the influence of the chemical structure and the interaction of the molecule with the metal nano-particle leading to the chemical selectivity of the effect are still under debate. The lines in the SER- spectra can directly be associated with the chemical structures and hence provide evidence for those parts of the molecule which contribute to the SER- polarizability tensor. This is further supported by the observation of reversible frequency jumps of distinct modes. The comparison of the spectra shows that the xanthene chromophore dominates the SER- spectra and wavelength selective excitation shows that resonance excitation contributes significantly to the spectral enhancement.

8 15:15 16:00 J.-J. Greffet Ecole Centrale Paris, France Surface waves in the near field : a new perspective Surface waves such as surface phonon polariton and surface plasmons have been widely studied in the seventies and eighties. Since the development of near-field optics, they can be observed. With the development of nanofabrication, we can use them to engineer new devices. The purpose of this talk is to present our latest results showing the importance of surface waves in many different domains. We will first discuss how transmission through a metallic film with slits can be resonantly enhanced. To explain this phenomenon, we will put forward the concept of mixed mode. A concept analogous to the concept of polarons. The mixed modes involved in the resonant transmission are surface plasmon modes and cavity modes in the slits. We will then show how thermally excited modes produce coherence in the near field. We will then show how this can be used to modify the emission properties of surfaces. Our final point will be the discussion of the role of surface waves on the local density of states. We will show that the surface plasmon dominate the density of states. A consequence is that the Casimir force between two metallic plates is entirely due to the surface plasmon

9 16:15 17:00 L. Novotny University of Rochester, USA Optics on the nanometer scale Nano-optics is motivated by the rapid advance of nanoscience and nanotechnology. It aims at exploring optical phenomena and techniques near or beyond the diffraction limit of light. Among the applications are highresolution microscopy and spectroscopy, nanolithography, and nanomanipulation. In this seminar I will discuss the motivation behind nanooptics and I will give an overview of topics pursued at the Institute of Optics.