Electrowetting-actuated optical switch based on total internal reflection

Abstract

In this paper we demonstrate a liquid optical switch based on total internal reflection. Two indium tin oxide electrodes are fabricated on the bottom substrate. A conductive liquid (Liquid 1) is placed on one side of the chamber and surrounded by a density-matched silicone oil (Liquid 2). In initial state, when the light beam illuminates the interface of the two liquids, it just meets the conditions of total internal reflection. The light is totally reflected by Liquid 2, and the device shows light-off state. When we apply a voltage to the other side of the indium tin oxide electrode, Liquid 1 stretched towards this side of the substrate and the curvature of the liquid-liquid interface changes. The light beam is refracted by Liquid 1 and the device shows light-on state. So the device can achieve the functions of an optical switch. Because the light beam can be totally reflected by the liquid, the device can attain 100% light intensity attenuation. Our experiments show that the response time from light-on (off) to light-off (on) are 130 and 132 ms, respectively. The proposed optical switch has potential applications in variable optical attenuators, information displays, and light shutters.

Large extinction ratio optical electrowetting shutter

“…The electrowetting effect is appealing as it enables transmissive, compact devices with minimal voltage requirements and no mechanical parts. The technique has been used to demonstrate lens and prism arrays for displays, imaging, tunable apertures and switches [5][6][7][8][9][10][11][12][13][14][15][16].…”

“…Although there are previous demonstrations of electrowetting-based displays [9], tunable irises [10], and switches [11][12][13][14], high extinction ratio (beyond 30 dB) shutters have not been demonstrated. There are many implementations of these functionalities, using opaque ink or oil droplets [5,9,11], tunable irises, and liquid interfaces operating around total internal reflection [14] (TIR). In contrast, the shutter reported here demonstrates 66 dB of extinction ratio and low voltage operation due to high quality materials and a unique geometry.…”