Darmstadt 2008 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 53: Poster Photonik

Q 53.2: Poster

Donnerstag, 13. März 2008, 16:30–19:00, Poster C2

Frequency Tripling and Interferometric Sensing with Ultra-Thin Optical Fibers — •Ulrich Wiedemann, Konstantin Karapetyan, Wolfgang Alt, and Dieter Meschede — Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn

We present the first results and the perspectives of our work devoted to investigation of ultra-thin optical fiber applications.

Our first goal is to achieve effective third harmonic generation (THG) using an ultra-thin fiber, which allows for light guidance over a large length while keeping the spot size small. In case of sub-wavelength fibers a significant portion of the power propagates outside the fiber, in the evanescent field. This high intensity light field in the space around the fiber is coupled to atoms with high third order nonlinearity to provide THG. To phase-match the fundamental and the frequency-tripled waves we compensate material dispersion with modal dispersion.

The second goal is to create an interferometric fiber sensor, in which the two legs of Mach-Zehnder scheme are represented by two different transverse fiber modes. One mode has a smaller evanescent field intensity than the other one, leading to different degree of influence of the surrounding medium on the optical path length. The two coherent modes are obtained and recombined using either non-adiabatic taper transition or long period fiber gratings.

For both experiments we are using standard single-mode fibers tapered down to diameters of about 500 nm at the length of 1--20 mm by flame-heating and stretching.