Optical beam steering using liquid-based devices

Non-mechanical optical beam steering has received extraordinary attention in recent decades because it can steer a beam to a desired direction or location without moving parts. As a novel member of the non-mechanical beam steering method family, the liquid-based beam steering method exhibits some intriguing features. For example, this method is polarization-independent and has wide broadband, low power consumption, simple structure, and long lifetime. Many studies have been devoted to realizing optical beam steering based on liquid-based devices. This paper reviews the recent progress in this field. First, from the perspective of the working principles, the technical approaches are divided into the following four types: electrowetting effect, dielectrophoresis effect, tunable liquid lenses, and hydraulic control. The optical beam steering using liquid-based devices based on the electrowetting effect is reviewed from multiple aspects, including different sidewall shapes, multiple actuation electrodes, multiple liquid-liquid interfaces, and droplet movement. Moreover, the performances of the optical beam steering using liquid-based devices are compared, which provide a reference for readers to select the working principle to design the beam steering devices. Next, some representative applications of the beam steering device using liquid-based devices are presented, including optical switch, three-dimensional display, laser radar, solar tracking, indoor light, and microscopy. Finally, the challenges and outlook of optical beam steering using liquid-based devices are discussed. This review aims to provide a snapshot of the current state of the research field of optical beam steering using liquid-based devices to attract additional attention.