Modal wavefront correctors based on nematic liquid crystals

Modal wavefront correctors based on nematic liquid crystals

Loktev, M.Y.

French, P.J. (promotor)

Electrical Engineering, Mathematics and Computer Science

2005-10-24

Modal wavefront correctors are active optical components for the compensation of aberrated optical wavefronts in a smooth and continuous way. They are traditionally represented by membrane and continuous faceplate deformable mirrors. This thesis is dedicated to the investigation and development of modal wavefront correctors based on nematic liquid crystals. The thesis introduces a new method for evaluating the average static correction performance of a wavefront corrector applied to compensation of random phase aberrations. Statistics of the random wavefronts are described by Kolmogorov's theory. The method allows a comparison of the static correction performances of different types of deformable mirrors and different actuator structures. A range of modal liquid crystal (LC) devices is considered, including adaptive spherical and cylindrical LC lenses and three different types of multi-element wavefront correctors. The research is focused on electro-optics of the devices, consideration of potentially useful control modes, development of algorithms of optimization and control, and alternative technologies for modal addressing of LCs. A control algorithm and software have been developed for a system for practical calibration of modal LC lenses. Feasibility of control using several degrees of freedom per actuator is demonstrated for both adaptive LC lenses and multi-element modal wavefront correctors. Two new approaches to forming of the modal-type phase profiles in LC layers are considered. The first one is based on spreading of the electric field in a thick dielectric substrate and the second one is based on a passive resistive network formed in a semiconductor silicon substrate. These approaches are illustrated with practically implemented devices. Comparison of the new technologies to a previously studied one is presented.

liquid crystals
phase modulators
wavefront correctors
adaptive optics

http://resolver.tudelft.nl/uuid:5210165d-f011-4cd3-8551-a1374641065d

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Institutional Repository

doctoral thesis

(c) 2005 M.Y. Loktev