Abstract
By combining polymer‐dispersed liquid crystal (PDLC) and holography, holographic PDLC (H‐PDLC) has emerged as a new composite material for switchable or tunable optical devices. Generally, H‐PDLC structures are created in a liquid crystal cell filled with polymer‐dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single‐step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H‐PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H‐PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state‐of‐the‐art of H‐PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro‐optical properties, the photonic applications, and the issues existed in H‐PDLCs.
Highlights
The Ferroelectric liquid crystals (FLCs) alignment is parallel to the polymer walls, which is different with the nematic-based H-polymer-dispersed liquid crystal (PDLC), where the nematic LC alignment is orthogonal to the polymer walls [27]
It is worth noting that, for the holographic PDLC (H-PDLC) transmission grating, it may be overmodulated in some cases
In the last several years, new applications have been developed based on H-PDLC, mainly in three aspects: (i) H-PDLC photonic crystals (PhCs), (ii) mirrorless lasing from dyedoped H-PDLC, and (iii) sensing applications
Summary
The discovery of polymers has much contributed to the change of day-to-day life. the use of polymers in human history dates back as early as Egyptian mummies. When the cloth was dried by exposure to the sunlight, the oil was converted into a protective polymer This was a typical application of photopolymerization. If higher functional monomers are used, a branched polymer will be formed (Figure 1(b)). Photopolymerization is a very flexible process and can be used in various technological applications such as photoresists in modern electronics In this process, a film of monomer mixture is placed on the surface of a silicon wafer and is illuminated through a photomask. The polymer-covered areas on the silicon wafer are used to resist chemical etching, resulting in integrated circuit formation or printed circuit board construction. This technology has allowed billions of transistors to be placed on a single integrated circuit
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
