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Q: Fachverband Quantenoptik und Photonik

Q 11: Laserentwicklung (Festkörperlaser II / Andere Laserquellen)

Q 11.6: Vortrag

Dienstag, 11. März 2008, 09:45–10:00, 3H

Novel approach for mode-selective polarization measurement and its application in few-mode fiber amplifier systems — •Niklas Andermahr¹, Thomas Theeg¹, and Carsten Fallnich² — ¹Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany — ²Institut für Angewandte Physik - WWU Münster, Corrensstraße 2, 48149 Münster, Germany

In the field of high-power fiber amplifiers large core diameters are of advantage to reduce the power density. However, these fibers often loose pure single transverse mode behavior. A better understanding of the propagation and interaction of higher order modes (HOMs) can help either to suppress or to use them.

We present a polarization-sensitive measurement of HOMs from a few-mode optical fiber using a three-mirror ring resonator. Measuring the power fraction as well as the polarization state we analyze a few-mode fiber amplifier system and show that the HOMs prefer orthogonal polarization states. This is explained, as the fiber modes thereby maximize the overlap of the intensity profile with the gain region.