Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 53: Ultrashort laser pulses III

Q 53.8: Talk

Thursday, March 20, 2014, 18:15–18:30, DO26 207

Transverse mode conversion of ultrashort pulses in optical fibers using optically induced long-period gratings — •Martin Schnack, Tim Hellwig, and Carsten Fallnich — Institute of Applied Physics, Westfälische Wilhelms-Universität Münster, Corrensstr. 2, 48149 Münster

We present our latest advances in numerical studies and experimental results on transverse mode conversion of femtosecond laser pulses in optical fibers using optically induced long-period fiber gratings.

The gratings are transiently generated by a high-power write beam, that excites a combination of transverse modes. By exploiting the Kerr-effect the spatial intensity pattern emerging from multi-mode interference is translated into a spatial refractive index modulation. A co-propagating, cross-polarized probe beam is converted from one to another transverse mode, if the grating period is suitable. We show first experimental results in a step-index fiber and discuss the limitations of distinguishing probe and write beam by polarization.

Furthermore, numerical studies employing graded-index fibers are presented. They allow utilizing write and probe pulses at different wavelengths and overcome current bandwidth limitations, making broadband mode conversion possible. In our numerical studies we demonstrate the optical switching capabilities based on this technique, providing a high modulation between the on and off state.