An electrowetting driven liquid tunable optical phase shifter

This paper reports on an electrowetting-based liquid tunable optical phase shifter. In this device, two immiscible liquid layers are placed adjacently with a planar boundary in between. By modifying the thickness of these layers, an optical path difference is induced, which results in a tunable phase shifter. A multi-layer SU-8 structure is used to realize the device. A phase shift of 171° with a rise-time of 110 ms was achieved by applying a 100 V AC signal to the electrowetting actuator embedded in the device.