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Proceedings Paper

Characterization of a liquid crystal spatial light modulator for beam steering
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Paper Abstract

The spatial light modulator (SLM) can be used to alter the phase of the wave front to achieve a deflection or a change in the shape of a laser beam. In this study a commercial nematic zero-twist liquid crystal SLM was evaluated. SLMs can be operated to produce pure phase modulation necessary for beam steering. For liquid crystals the relation between applied voltage and phase modulation is highly non-linear due to the relation between the voltage driven molecular tilt angle and extraordinary refractive index. To compensate for this effect we optimized and examined look-up tables (LUT) that realize the inverse of the phase response. It was found that the factory LUT improved the power ratio between the zero order and the first order peaks five times compared to the case without using an LUT, however, further improvement of this ratio of two was reached using an LUT optimized from the measured phase response of the SLM. The discrete phase modulation results in a stepped, non-ideal blazed grating that alters the relative power of the available steering angles. To obtain optimal performance these effects must be analyzed for different bit depths and preliminary results of such quantization effects are discussed.

Paper Details

Date Published: 4 June 2002
PDF: 10 pages
Proc. SPIE 4632, Laser and Beam Control Technologies, (4 June 2002); doi: 10.1117/12.469766
Show Author Affiliations
Emil J. Haellstig, Swedish Defence Research Agency (Sweden)
Lars Sjoeqvist, Swedish Defence Research Agency (Sweden)
Mikael Lindgren, Swedish Defence Research Agency (Sweden)

Published in SPIE Proceedings Vol. 4632:
Laser and Beam Control Technologies
Santanu Basu; James F. Riker, Editor(s)

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