Liquid-crystal phase modulators for active micro-optic devices

Alan Purvis; Geoffrey Williams; Norman J. Powell; Michael G. Clark; Michael C.K. Wiltshire

doi:10.1117/12.44687

1 June 1991 Liquid-crystal phase modulators for active micro-optic devices

Alan Purvis, Geoffrey Williams, Norman J. Powell, Michael G. Clark, Michael C.K. Wiltshire

Proceedings Volume 1455, Liquid-Crystal Devices and Materials; (1991) https://doi.org/10.1117/12.44687
Event: Electronic Imaging '91, 1991, San Jose, CA, United States

Abstract

At present there is considerable interest in fixed binary optic systems made by micro- fabrication techniques to produce arrays of miniature optical components for the control of light. These devices essentially replicate the phase curvature of their macroscopic counterparts by a 2n level substrate etched using n binary masks, the approximation being tolerated because of the multiplicity achieved. There exists a corresponding set of active binary devices where instead of the phase modulation being produced by substrate depth changes, micro electrodes modulate the orientation of birefringent molecules with applied binary voltages. This paper reviews some of the experimental devices which have been made using this approach such as phase gratings, prisms and lenses. It is shown how the analog dependence of molecular orientation on voltage actually improves the efficiency of the devices in addition to enabling an adaptive switching capability. An example is given of how a smoothly varying phase profile in a small region can be produced by allowing one of the electrodes to conduct above the ground plane and thereby drop volts and induce a continuous phase gradient. Furthermore electrostatic edge effects at the finely spaced electrodes can be exploited at the sharp binary edges produced by the lithographic mask to suppress the higher order diffraction orders which can limit the performance of these systems.

Citation Download Citation

Alan Purvis, Geoffrey Williams, Norman J. Powell, Michael G. Clark, and Michael C.K. Wiltshire "Liquid-crystal phase modulators for active micro-optic devices", Proc. SPIE 1455, Liquid-Crystal Devices and Materials, (1 June 1991); https://doi.org/10.1117/12.44687

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