Electrowetting Liquid Lens Oscillations for Optical Applications

Abstract

The ability to modulate the phase of a transmitted beam over space and time is valuable in optical systems. Adaptive optics systems, such as retina imaging systems, can require dynamic wavefront correction and shaping of coherent beams. A two liquid cell with dissimilar refractive indices and a user defined meniscus profile can modulate a wavefront with polarization insensitivity. This can be done in transmission, and with cost-effective materials, by controlling the meniscus profile with electrowetting. While the use of a static meniscus profile shape in electrowetting lenses is well documented, the use of oscillations on the meniscus profile has just recently begun to be explored. The superposition of electrowetting liquid lens oscillations can form an arbitrary profile for user defined wavefront correction or beam shaping. If only one electrode around the liquids is used, radially symmetric oscillations are present, while multiple electrodes enables asymmetric oscillation patterns. Models for the dynamics of an electrowetting liquid lens are given and discussed in this thesis. A method for measuring the liquid-liquid meniscus profile over space and time using digital holographic interferometry (DHI) is detailed. Measurements of a commercial electrowetting liquid lens driven from f=10-200 Hz are presented and analyzed. A frequency response is given, as well as an analysis of the oscillation frequencies and profile spatial spectrum. Non-linear effects that were observed at higher forcing amplitudes are noted. A new application application of an oscillating electrowetting liquid lenses in random phase mask optical image cryptography is also presented. Through the presentation of experimental, theoretical and numerical work, the usefulness of oscillating electrowetting lenses for optical applications is investigated.