Title

Nonlinear Refraction And Optical Limiting In Thick Media

Keywords

Nonlinear Refraction; Optical Limiting; Z-Scan; Aberration-Free; Approximation; Self-Focusing; Internal Self-Action; Cs2; N2 Measurements; Single-Beam; Cs2; Optics

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.

Publication Title

Optical Engineering

Volume

30

Issue/Number

8

Publication Date

1-1-1991

Document Type

Article

Language

English

First Page

1228

Last Page

1235

WOS Identifier

WOS:A1991FZ61200023

ISSN

0091-3286

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