Hannover 2003 – wissenschaftliches Programm

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Q: Quantenoptik

Q 34: Optische Messtechnik und Pr
äzisionsmessungen

Q 34.3: Vortrag

Donnerstag, 27. März 2003, 11:30–11:45, F142

Fast measurement of tapered fiber profiles in the submicrometer range — •Florian Warken and Harald Giessen — Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn

For the performance of tapered fibers as white light sources it is crucial to know the exact waist diameter along the fiber.

To measure the fiber diameter, evaluation of a diffraction pattern can be utilized. For transparent media such as glass fibers, the sinc²-diffraction pattern (black strip model) does not give proper results. The reason is the additional light transmitted and focussed by the thin fiber waist. This light interferes with the diffracted light. Therefore, a rigorous electromagnetic calculation has to be used [1]. Since there is no simple analytical solution for the modified diffraction pattern extrema, one has to solve this problem numerically.

The optical diffraction setup is using a cylinder lens telescope in order to get a line focus. Using a CCD camera, a frame grabber, and a computerized code we can obtain the whole fiber profile with submicron accuracy by just recording and analyzing a single diffraction pattern. Our method works well from less than 1 micrometer to a few micrometers diameter. When drawing a tapered fiber, we found that the diameter varies by about 15% along the waist.

[1] D.J. Butler and G.W. Forbes, Appl. Opt. 37. 2598 (1998).