Self-activating liquid crystal devices for smart laser protection

Abstract

Lasers are now extensively used in a multitude of optical devices and photonic systems spanning from sensing, communication, entertainment, medical surgery to military applications. Direct accidental or intentional exposures to high power lasers may lead to severe temporary or even permanent harm of human eye, skin, or optical sensors. The effective laser protection and shielding are currently not only a subject of scientific research but also a potential public safety issue, therefore there is an urgent need to develop the intelligent laser protection devices for keeping human eyes, optical sensors, and other sensitive components from these unintended or intended damages by laser radiations without warning. Self-activating liquid crystal devices undoubtedly represent such an elegant example because they could be autonomously activated to block or attenuate the lasers when the laser intensity is higher than a maximum permissible exposure value. This review is devoted to summarising the up-to-date significant advances of selfactivating liquid crystal devices for potential smart laser protection, including twist-aligned nematic liquid crystal devices, liquid crystal cored waveguide fibre arrays, and photovoltaic/ pyroelectric-hybridised liquid crystal devices. Finally, the review concludes with the perspectives and challenges for the future development of self-activating liquid crystal devices. It is anticipated that this glimpse and further endeavours in the emerging field will help the researchers from different backgrounds towards the fabrication of highly efficient laser protection devices, their real-world widespread applications and beyond. ARTICLE HISTORY

Iridescence in nematics: Photonic liquid crystals of nanoplates in absence of long-range periodicity

“…Among various types of ordered nanoarchitectures, photonic liquid crystals (PLCs) of 2D nanomaterials have attracted recent attention owing to the ability of dynamically interacting with the light of interest to achieve brilliant reflection colors (11). Generally, the color of PLCs originates from the periodic structures with long-range positional ordering, such as lamellar or helical arrangement (12)(13)(14)(15)(16)(17). In particular, lamellar structure is one of the most studied designs for fabricating photonic materials of 2D building blocks due to the structural similarity to natural nacre and pearls (18).…”

Recent Progress in Two-Dimensional Nanomaterials for Laser Protection

“…Figure 2 displays the typical graphene-like ultrathin 2D nanomaterials. These atomic-scale thick materials have a large surface area and outstanding thermal and electrical conductivity, superior flexibility, and superior nonlinear optical response, endowing it with the promising application scope in the field of supercapacitors [31][32][33][34], energy storage devices [35][36][37][38], organic light-emitting diodes (OLEDs) [39][40][41], information storage devices [42][43][44][45], optical limiters, [46][47][48][49][50][51][52][53] and others. Due to the extended conjugate sp 2 π-system and linear dispersion relation of its electronic band structure, graphene, the most representative 2D nanomaterial, and its derivatives, possesses the ultra-broadband resonate NLO response and the ultrafast carrier relaxation dynamics, which make it suitable for the preparation of solution-or solid-state optical limiters.…”

Response Improvement of Liquid Crystal-Loaded NRD Waveguide Type Terahertz Variable Phase Shifter

“…On the other hand, owing to unique electro-optical properties and optical properties, liquid crystals (LCs) are known to be widely used not only in optical applications, such as displays, lasers, or optical modulators, but also in various fields [2][3][4][5]. In recent years, LCs have attracted attention as one of the high-frequency materials in which transmission characteristics can be changed by controlling and adjusting permittivity [6,7].…”