Low scattering and fast response polymer brush-stabilized liquid crystal microlens array with tunable focal length

Abstract

Introducing polymers into liquid crystal (LC) devices is an effective way to increase the response speed, but it can also cause additional scattering. A scattering-free and fast-response LC microlens array (LCMLA) based on surface-initiated polymerization (SIP) is demonstrated. Unlike the conventional fabrication of the polymer network liquid crystal (PNLC), the initiator is encapsulated in an alignment layer on the surface of the substrate, separate from the reacting monomers. Ring array patterned electrodes, carefully designed, generate a non-uniform electric field, which in turn induces a gradient refractive index distribution in the LC layer. Upon UV polymerization, the reaction initiates at active sites on the surface, and polymer fibers grow directionally from the substrate, resembling bush-like structures confined to the surface layer. LCMLAs fabricated using this method exhibits a haze of only 13.8 %, offering higher transmittance compared to conventional PNLC MLA. Due to these characteristics, the polymer brush-stabilized liquid crystal (PBSLC) MLA has better imaging performance. Additionally, the response time of the PBSLC MLA is 2.32 ms. Consequently, this PBSLC MLA hold significant potential for applications in the optical communication, fast-switching displays, beam steering and adaptive optics.