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Proceedings Paper

Index-mismatch scattering approach to optical limiting
Author(s): Gregory J. Exarhos; Kim F. Ferris; Charles F. Windisch; Brian J. Bozlee; Steven M. Risser; Simone L. van Swam
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Paper Abstract

A densely packed bed of alkaline earth fluoride particles percolated by a fluid medium has been investigated as potential index-matched optical limiter in the spirit of a Christiansen-Shelyubskii filter. Marked optical limiting was observed through this transparent medium under conditions where the focused second-harmonic output of a Q-Switched Nd:YAG laser was on the order of about 1 J/cm2. An open- aperture Z-scan technique was used to quantify the limiting behavior. In this case, the mechanism of optical limiting is thought to be a nonlinear shift in the fluid index of refraction, resulting in an index mismatch between the disparate phases at high laser fluence. This induced mismatch appears to be promoted by localized electric field enhancement present near the sharp edges at the crystallite/fluid boundaries. Index mismatch between the two phases leads to multiple reflections, loss of coherence, and a significant transmission decrease due to Mie scattering. The presence of many boundaries significantly amplifies the effect. The role of thermally induced changes in refractive index for this system appears to be relatively small in pulsed-laser experiments. However, cw-laser blocking was achieved by a thermal mechanism when an absorber (iodine) was dissolved in the liquid phase. Fundamental studies of such systems are used to verify theoretical predictions of the limiting effect, and aid in the design and development of improved limiters based upon this optical deflection approach.

Paper Details

Date Published: 12 April 2001
PDF: 12 pages
Proc. SPIE 4347, Laser-Induced Damage in Optical Materials: 2000, (12 April 2001); doi: 10.1117/12.425012
Show Author Affiliations
Gregory J. Exarhos, Pacific Northwest National Lab. (United States)
Kim F. Ferris, Pacific Northwest National Lab. (United States)
Charles F. Windisch, Pacific Northwest National Lab. (United States)
Brian J. Bozlee, Univ. of Great Falls (United States)
Steven M. Risser, Battelle Columbus Lab. (United States)
Simone L. van Swam, Northwestern Univ. (United States)


Published in SPIE Proceedings Vol. 4347:
Laser-Induced Damage in Optical Materials: 2000
Gregory J. Exarhos; Arthur H. Guenther; Mark R. Kozlowski; Keith L. Lewis; M. J. Soileau, Editor(s)

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