Electrowetting optical switch with large aperture tuning range

In this paper, we propose an optical switch by deforming the shape of the liquid droplet. The optical switch consists of two immiscible liquids. The dye-doped water is conductive, while the clear liquid is insulating. In the voltage-off state, incident light can pass through the circular aperture formed of clear liquid. When the voltage is applied to the liquids, the surrounding dye-doped water pushes to the side wall because of the effect of electric field force. So, the diameter of the circular aperture is rapidly reduced, and the incident light is absorbed by the dye-doped water. Our results show that the device can obtain an optical attenuation (~350:1) and reasonable response time (~320 ms). The diameter of the aperture can be largely tuned from ~0.5 to ~6.2 mm as the applied voltage is changed from ~25 to ~65 V. The proposed optical switch has potential applications in light shutters, tunable irises, and variable optical attenuators.