High Performance Beam Steering via Tunable Liquid Prisms

The use of liquids for the manipulation of light has many advantages over their conventional solid counterparts. With the emergence of microfluidic technologies to control fluid interfaces, various devices capable of replacing conventional optical components have been developed. Because liquids are intrinsically smooth and can change shape or form, they have been utilized for highly versatile components to manipulate light with high degrees of control using optofluidic technologies. Liquid lenses and beam steering devices are among the typical optofluidic devices that have gained much interest over recent years. In this work, we present high-performance tunable liquid prisms capable of wide beam steering of incoming light. By using the electrowetting phenomena, we are able to modulate the fluid-fluid interface at which beam steering occurs. Optical analyses were conducted to study the effect of liquid selection in the effectiveness of our prisms. Furthermore, the double-stacked prism configuration is proposed to achieve wide beam steering and its performance is compared with that of a single prism for different liquid selections. Finally, our analytical studies have been experimentally demonstrated. We successfully fabricated the tunable liquid prism filled with water and 1-bromonaphthalene (1-BN). Due to large refractive index difference between two liquids (n_water = 1.33 and n_1−BN = 1.65 at λ = 532 nm), high-performance beam steering was enabled. With an apex angle of 25°, we were able to experimentally demonstrate a beam steering of β ≤ 8.82° with the single prism configuration. It was significantly improved up to β ≤ 17.04° for the double-stacked prism.