Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow response time of nematic liquid crystal (LC) microlenses has been a significant technical barrier to practical applications and commercialization. LC/polymer composites, consisting of LC and monomer, are an important extension of pure LC systems, which offer more flexibility and much richer functionality than LC alone. Due to the anchoring effect of a polymer network, microlenses, based on LC/polymer composites, have relatively fast response time in comparison with pure nematic LC microlenses. In addition, polymer-stabilized blue phase liquid crystal (PS-BPLC) based on Kerr effect is emerging as a promising candidate for new photonics application. The major attractions of PS-BPLC are submillisecond response time and no need for surface alignment layer. In this paper, we review two types of fast-response microlenses based on LC/polymer composites: polymer dispersed/stabilized nematic LC and polymer-stabilized blue phase LC. Their basic operating principles are introduced and recent progress is reviewed by examples from recent literature. Finally, the major challenges and future perspectives are discussed.

We demonstrate a flat polymeric lenticular microlens array using a mixture of rod-like diacrylate monomer and positive dielectric anisotropy nematic liquid crystal (LC). To create gradient refractive index profile in one microlens, we generate fringing fields from a planar top electrode and two striped bottom electrodes. After UV stabilization, the film is optically anisotropic and can stand alone. We then laminate this film on a 90° twisted-nematic LC cell, which works as a dynamic polarization rotator. The static polymeric lenticular lens exhibits focusing effect only to the extraordinary ray, but no optical effect to the ordinary ray. Such an integrated lens system offers several advantages, such as low voltage, fast response time, and temperature insensitivity, and can be used for switchable 2D/3D displays.

An optical switch based on a deformable liquid droplet is demonstrated. The device consists of a clear liquid droplet surrounded by a black liquid. In the voltage-off state, the incident light is absorbed by the black liquid. As the voltage increases, the dielectric force reshapes the droplet by uplifting its dome. As the dome touches the top substrate, a clear channel is opened, allowing the incident light to pass through. Once the voltage is removed, the deformed droplet relaxes back to its original shape and the channel is closed. Devices based on such an operation mechanism have potential applications in light shutters, variable optical attenuators, adaptive irises, and displays.

We demonstrated a novel optical switch with a reconfigurable dielectric liquid droplet. The device consists of a clear liquid droplet (glycerol) surrounded by a black liquid (dye-doped liquid crystal). In the voltage-off state, the incident light passing through the clear liquid droplet is absorbed by the black liquid, resulting in a dark state. In the voltage-on state, the dome of the clear liquid droplet is uplifted by the dielectric force to form a light pipe which in turn transmits the incident light. Upon removing the voltage, the droplet recovers to its original shape and the switch is closed. We also demonstrated a red color light switch with ~10:1 contrast ratio and ~300 ms response time. Devices based on such an operation mechanism will find attractive applications in light shutter, tunable iris, variable optical attenuators, and displays

We demonstrate an adaptive mechanical-wetting lens with a concentric reservoir to reduce image aberrations and overcome the gravity effect. This lens adopts liquid pressure to change the interface between two immiscible liquids which, in turn, changes the focal length of the resultant liquid lens. Good optical performance, high resolution, and a wide dynamic range of both positive and negative optical power are achieved. Since no PDMS is employed, such lenses can extend their working range to infrared region by choosing proper liquids.

We demonstrate a liquid droplet whose surface profile can be reshaped by voltage. As the dielectric force increases, the dome of a liquid droplet could touch the top substrate and become flat. While the voltage is removed, the droplet recovers to its original spherical shape. By choosing proper liquids, the required voltage for such a shape change is relatively low and the transition speed is fast. Potential application of such a deformable droplet for optical beam control is discussed.