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Optical Engineering

Nonlinear refraction and optical limiting in "thick" media
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Paper Abstract

We experimentally and theoretically investigate optical beam propagation in nonlinear refractive materials having a thickness greater than the depth of focus of the input beam (i.e., internal self-action). A simple model based on the "constant shape approximation" is adequate for analyzing the propagation of laser beams within such media under most conditions. In a tight focus geometry, we find that the position of the sample with respect to the focal plane, z, is an important parameter in the fluence limiting characteristics of the output. The behavior with z allows us to perform a "thick sample Z-scan" from which we can determine the sign and magnitude of the nonlinear refraction index. In CS2, we have used this method to independently measure the negative thermally induced index change and the positive Kerr nonlinearity with nanosecond and picosecond CO2 laser pulses, respectively. We have experimentally examined the limiting characteristics of thick CS2 samples that qualitatively agree with our analysis for both positive and negative nonlinear refraction. This analysis is useful in optimizing the limiting behavior of devices based on self-action.

Paper Details

Date Published: 1 August 1991
PDF: 8 pages
Opt. Eng. 30(8) doi: 10.1117/12.55902
Published in: Optical Engineering Volume 30, Issue 8
Show Author Affiliations
Mansoor Sheik-Bahae, Univ. of Central Florida (United States)
Ali A. Said, Univ. of Central Florida (United States)
David J. Hagan, Univ. of Central Florida (United States)
M. J. Soileau, Univ. of Central Florida (United States)
Eric W. Van Stryland

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