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Proceedings Paper

Characterization of depolarizing fringing fields of a liquid crystal spatial light modulator for laser beam steering
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Paper Abstract

A commercial linear one-dimensional, 1x4096 pixels, zero-twist nematic liquid crystal spatial light modulator (SLM), giving more than 2π phase modulation at λ = 850 nm, was evaluated for beam steering applications. The large ratio (7:1) between the liquid crystal layer thickness and pixel width gives rise to voltage leakage and fringing fields between pixels. Due to the fringing fields the ideal calculated phase patterns cannot be perfectly realized by the device. Losses in high frequency components in the phase patterns were found to limit the maximum deflection angle. The inhomogeneous optical anisotropy of the SLM was determined by modelling of the liquid crystal director distribution within the electrode-pixel structure. The effects of the fringing fields on the amplitude and phase modulation were studied by full vector finite-difference time-domain simulations. It was found that the fringing fields also resulted in coupling into an unwanted polarization mode. Measurements of how this mode coupling affects the beam steering quality were carried out and the results compared with calculated results. A method to compensate for the fringing field effects is discussed and it is shown how the usable steering range of the SLM can be extended to ± 2 degrees.

Paper Details

Date Published: 6 February 2004
PDF: 11 pages
Proc. SPIE 5237, Optics in Atmospheric Propagation and Adaptive Systems VI, (6 February 2004); doi: 10.1117/12.510990
Show Author Affiliations
Emil J. Haellstig, Swedish Defence Research Agency (Sweden)
Torleif Martin, Swedish Defence Research Agency (Sweden)
Johan Stigwall, Chalmers Univ. of Technology (Sweden)
Lars Sjoqvist, Swedish Defence Research Agency (Sweden)
Mikael Lindgren, Swedish Defence Research Agency (Sweden)

Published in SPIE Proceedings Vol. 5237:
Optics in Atmospheric Propagation and Adaptive Systems VI
John D. Gonglewski; Karin Stein, Editor(s)

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