Self-Centering Effect of a Thickness-Gradient Dielectric of an Electrowetting Liquid Lens

• Published in: IEEE photonics technology letters 2013-03, Vol.25 (6), p.623-625
• Main Authors: Yangkyu Park, Seungwan Seo, Gruenberg, P., Jong-Hyun Lee
• Format: Article
• Language: English
• Subjects: Adaptive optics; Conferences; Dielectric measurements; Dielectrics; Errors; Fiber optics; Lenses; Liquids; Mass production; Off-centering error; Optical device fabrication; Optical fibers; reflow; self-centering; Semiconductors; thickness-gradient dielectric; Voltage measurement
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2013.2247392

The experimental verification of the electrical centering effect of a thickness-gradient dielectric in an electrowetting micro liquid lens is presented. This device features an efficient centering scheme and easy fabrication. Two types of liquid lenses with a thickness-gradient and uniform-thickness dielectric layer are fabricated and experimentally compared. Repeatability tests for the off-centering error of the fabricated lenses are carried out for the same tuning range of focal length. The acquired maximum off-centering error for a thickness-gradient dielectric layer is 20 μm (equivalent to a tilt angle of 0.05°), whereas the lens with a uniform-thickness dielectric layer is 162 μm. Off-centering is considerably improved, even compared to the mechanical centering method using a conical geometry (50 μm). Moreover, the thickness-gradient dielectric layer could be easily fabricated using a photoresist reflow process, which reduces the required processing steps, making it suitable for mass production.