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Proceedings Paper

Mode analysis using the correlation filter method
Author(s): Daniel Flamm; Christian Schulze; Darryl Naidoo; Andrew Forbes; Michael Duparré
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Paper Abstract

We introduce the correlation filter method for measuring the modal power spectrum of multi-mode beams. The method is based on an optical filter performing the integral relation of correlation. This filter is realized as a computer-generated hologram with a specifically designed transmission function based on the spatial distribution of the set of modes under test. The beam that is illuminating the hologram is generating a diffraction pattern containing information about modal amplitudes and intermodal phase differences. We will show that a simple single-shot intensity measurement is sufficient to gain the information about modal amplitudes and phases from the diffraction pattern which result in the ability to reconstruct the optical field under test. Beside a detailed presentation of the measurement process, the setup and the design of the correlation filters, the major advantage of the method, the ability to perform real-time measurements is introduced. As a test system, we investigate the guided modes of a few mode multi-mode fiber and show fast changing modal coupling processes. Thereby, we show measurement results of online-monitoring the reconstructed optical field of the beam under test.

Paper Details

Date Published: 5 March 2013
PDF: 9 pages
Proc. SPIE 8637, Complex Light and Optical Forces VII, 863717 (5 March 2013); doi: 10.1117/12.2004557
Show Author Affiliations
Daniel Flamm, Friedrich-Schiller-Univ. Jena (Germany)
Christian Schulze, Friedrich-Schiller-Univ. Jena (Germany)
Darryl Naidoo, Council for Scientific and Industrial Research National Laser Ctr. (South Africa)
Andrew Forbes, Council for Scientific and Industrial Research National Laser Ctr. (South Africa)
Univ. of KwaZulu-Natal (South Africa)
Michael Duparré, Friedrich-Schiller-Univ. Jena (Germany)

Published in SPIE Proceedings Vol. 8637:
Complex Light and Optical Forces VII
Jesper Glückstad; David L. Andrews; Enrique J. Galvez, Editor(s)

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