Bidirectional optical switch based on electrowetting

In this paper, we demonstrate a bidirectional optical switch based on electrowetting. Four rectangular polymethyl methacrylate substrates are stacked to form the device and three ITO electrodes are fabricated on the bottom substrate. A black liquid droplet is placed on the middle of the ITO electrode and surrounded by silicone oil. When we apply a voltage to one ITO electrode, the droplet stretches and moves in one direction and a light beam is covered by the stretched droplet, while the droplet yields a space to let the original blocked light pass through. Due to the shift of the droplet, our device functions as a bidirectional optical switch. Our experiment shows that the device can obtain a wide optical attenuation from ∼1 dB to 30 dB and the transmission loss is ∼0.67 dB. The response time of the device is ∼177 ms. The proposed optical switch has potential applications in variable optical attenuators, electronic displays, and light shutters.