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Proceedings Paper

Influence of fiber injection on square fiber optic homogenizer
Author(s): Todd Lizotte
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Paper Abstract

This paper documents the development of a laser beam homogenizer using a large, square fiber (channel integrator, kaleidoscope). The main effort addresses the beam injection issues for a three fiber system. The purpose of using three fibers is to split the input beam into three beams for use in an industrial laser process. It has been observed by the researchers in the laser beam shaping community, that strong patterns can be observed in the output irradiance of the output irradiance of optical fibers when the laser source is focused onto the entrance face of the fiber. This is due to the fact that although the mode volume of the fiber uniformly filled, the phase is not suitably randomized. This is analogous to the fact that summing a large number of Fourier series terms with uniform amplitude and phase will approximate a delta function. If the phases are randomized, the result will be a uniform speckle pattern. The Fourier components correspond to the modes of the fiber. Further, in the case of uniform phase input, the phase of the different modes will change as the light propagates down the fiber due to the difference in mode propagation velocities. But, the phase will not assume a random distribution if the fiber is not perturbed. This problem is frequently alleviated using mode scramblers, which usually employ bends or micro-perturbations of the fiber path. The problem can also exist if the mode volume of the fiber is not uniformly filled. This will happen if the source NA does not match the NA of the fiber. This paper will compare and contrast two methods of fiber injection; a traditional focused beam approach and a lenslet array beam integrator approach. Each design will be outlined and the performance results will be discussed to determine how well each method filled the modes of the square fiber.

Paper Details

Date Published: 14 May 2010
PDF: 10 pages
Proc. SPIE 7717, Optical Modelling and Design, 77170C (14 May 2010); doi: 10.1117/12.855998
Show Author Affiliations
Todd Lizotte, Hitachi Via Mechanics USA, Inc. (United States)

Published in SPIE Proceedings Vol. 7717:
Optical Modelling and Design
Frank Wyrowski; John T. Sheridan; Jani Tervo; Youri Meuret, Editor(s)

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