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Proceedings Paper

Z-scan measurement on liquid crystals using top-hat beams
Author(s): W. Zhao; Julie H. Kim; Peter Palffy-Muhoray
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Paper Abstract

The conventional Z-scan technique using Gaussian beams for measuring intensity dependent optical nonlinearities is extended to allow the use of beams with top-hat profile. Potential applications of the top-hat beam Z-scan technique include the measurement of (chi) (3) over a wide spectrum which typically requires the use of a dye laser. We present a graphical method which allows straightforward determination of both the real and imaginary components of (chi) (3) from Z-scan data. Using the top-hat Z-scan scheme, we have measured (chi) (3) as function of wavelength for typical liquid crystal materials, over the visible spectrum. The spectral behavior of (chi) (3) gives insight into the underlying physical process on various time scales. We also present results of pump-probe measurements of the nonlinear absorption coefficient of the nematic liquid crystal 5CB. Our results indicate that the nonlinear absorption process in the nanosecond time regime is dominated by the two-photon excited-state absorption process. The time constant of this process is estimated from experimental data. A simple model is presented which agrees with our observations.

Paper Details

Date Published: 6 July 1994
PDF: 17 pages
Proc. SPIE 2229, Nonlinear Optical Materials for Switching and Limiting, (6 July 1994); doi: 10.1117/12.179579
Show Author Affiliations
W. Zhao, Kent State Univ. (United States)
Julie H. Kim, Kent State Univ. (United States)
Peter Palffy-Muhoray, Kent State Univ. (United States)


Published in SPIE Proceedings Vol. 2229:
Nonlinear Optical Materials for Switching and Limiting
M. J. Soileau, Editor(s)

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