Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 28: Quantum Effects III

Q 28.1: Talk

Thursday, April 5, 2001, 17:30–17:45, H 3010

Coupling of a near-field probe to whispering-gallery modes in a microsphere — •Stephan Götzinger, Oliver Benson, and Vahid Sandoghdar — Universität Konstanz, Fachbereich Physik und Optik-Zentrum Konstanz, Fach M696, D-78457 Konstanz, Germany

Recently, novel light sources made from semiconductor nanoparticles as active material coupled to individual modes of microsphere resonators via the evanescent field, were proposed [1]. In experimental realizations of these light sources, it is very important to precisely control the coupling in order to achieve optimal coupling efficiency without degrading the Q-factor. Here, we report on a new experiment where we couple a fiber tip to individual modes of a microsphere resonator. In order to achieve coupling, the tapered fiber tip is placed close to the sphere surface and light from the evanescent field on the sphere surface scatters into the fiber. We control the tip-sphere distance via the shear-force mechanism common in Scanning Near-field Optical Microscopy (SNOM). This method allows us to map the local intensity profile of the whispering-gallery mode and, additionally, we can observe the influence of the fiber tip on the Q-factor. In future experiments we replace the bare fiber tip with a fiber tip that has a single quantum dot or a single molecule attached to its end. This opens the way to experimental realization of novel light sources which couple nanoscopic amounts of active material to optical microresonators. [1] M. Pelton and Y. Yamamoto, Phys. Rev. A 59, 2418 (1999).