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The enthusiasm for research on liquid crystal random lasers (LCRLs) is driven by their unusual optical properties and promising potential for broad applications in manufacturing, communications, medicine and entertainment. From this perspective, we will summarize the most attractive advances in the development of LCRLs in the last decade and propose future prospects. This article will begin with a fundamental description of LCRLs, including the principle of laser generation and a description of LC substances. Then, we spend several chapters on the lasing performance control methods of LCRLs, including random lasing wavelength, threshold, and polarization properties. In addition, we analyze how the LC chiral agent structures, LC core-shell structures and new light-amplifying materials affect the design of LCRL devices. In the last chapter, we discuss the application of LCRLs in 3D displays, information encryption, biochemical sensing and other optoelectronics devices and finally end the perspective with LCRLs' likely directions in future research.

A series of one-armed cholesterol-linked azobenzene molecules named CholXAzo with different spacers were synthesized, in which Chol6Azo was found to have induced blue phases (BPs) with a concentration of 4.0 wt%. Under irradiation of 385 nm UV light with a density of 15.0 mW cm(-2), photo-responsive behaviour of the 4.0 wt% Chol6Azo doped sample named B3 shows a sensitive temperature dependence, which means that at 38.0 °C a phase transition from BPs to the isotropic phase is induced; however, at 33.0 °C, this phase transition does not take place. Results from the research show that the optically binary phase transition behaviour of B3 is sensitive to the isomerization degree of Chol6Azo, which is closely related to the stability of the BP structure and there is a critical isomerization degree of 13.7% for the phase transition of the B3 liquid crystals. Further POM observation shows that the liquid crystal samples doped with different concentrations of Chol6Azo have an increasing transition temperature for photo-induced phase transition from the BP to the isotropic phase along with the increasing concentration of Chol6Azo, which are found to have the same changing tendency with phase transition temperature from the isotropic phase to BPs and a phase diagram is made to map the optically binary behaviour of Chol6Azo doped blue phase liquid crystals. At last, a simple pattern with the BP and the isotropic phase arranged at an interval was made in this optically binary liquid crystalline blue phase under a suitable photomask.

Liquid‐crystal random lasers (LCRLs) represent a burgeoning field in soft‐matter photonics, holding promise for ushering in an era of ultrathin, versatile laser sources. Such lasers encompass a multitude of remarkable features, including wide‐band tunability, large coherence area and, in some cases, multidirectional emission. In this paper, an LCRL is developed by doping a laser dye, pyrromethene 597 (PM597), into cholesteric LC, but achieving a wide‐range wavelength‐controllable (560–720 nm) bandgap lasing through voltage control. Bandgap lasing intriguingly occurs in media with extremely low dye gain, which is mainly contributed by the extremely high photon density of states (DOS) at the edge of the LC bandgap. In addition, the utilization rate of the fluorescence spectrum (550–750 nm) of laser dye PM597 is as high as 80%. The multivariate linear regression model is used to characterize the inherent relationship between the lasing intensity emitted by LC and the photon DOS, fluorescence quantum yield, and internal scattering under specific pumping energy. This model shows the potential to predict the critical conditions of laser emission accurately and provides the capability to design and fabricate large‐scale multifunctional responsive photonic crystals using a simple fabrication procedure. [ABSTRACT FROM AUTHOR]

Random lasers (RLs), which possess peculiar advantages (e.g., emission and coherence tunable) over traditional lasers with optical resonators, have witnessed rapid development in the past decades. However, it is still a challenge to tune the lasing peak of an RL over a wide range. Here, a temperature-dependent Förster resonance energy transfer (FRET) RL is demonstrated in pyrromethene 597 (PM597, "donor") and Nile blue (NB, "acceptor") doped chiral liquid crystals. By changing the temperature that drives the liquid crystal bandgap shift, our RL device exhibits a lasing output change from 560 nm (yellow) to 700 nm (red). While the intrinsic FRET efficiency between PM597 and NB is relatively low, the red lasing is weak. By introducing gold nanorods (GNRs) into these RL devices and utilizing GNRs' localized surface plasmon resonance (LSPR) effect, the efficiency of FRET transfer is increased by 68.9%, thereby reducing the threshold of the RL devices. By tuning the longitudinal LSPR to match the emission wavelength of NB, the best 200-fold lasing intensity enhancement is recorded. Our findings open a pathway toward realizing LSPR-enhanced FRET tunable RLs and broaden the range of their possible exploration in photonics research and technologies. [ABSTRACT FROM AUTHOR]

In waveguided nematic liquid crystal random lasers (NLCRLs), we realize polarized random laser (RL) emission and discover that the waveguide effect reduces the transmission loss of the RL whose polarization is parallel to the liquid crystal molecules (LCMs). Compared with the traditional liquid crystal random lasers, the waveguide NLCRLs can achieve the regulation of RLs strength, polarization, and wavelength in the same structure. The electric field can drive the rotation of LCMs to control the RL polarization and intensity. The drop of horizontal polarization laser and the increase of vertical polarization laser prove the role of the waveguide effect. In addition, the disorder of the waveguided NLCRLs is highly sensitive to temperature, which makes it easy to control the wavelength and intensity of the RL. As the temperature rises, the waveguide effect is weakened, resulting in a weakening of the restriction along liquid crystal (LC) cell normal direction. The reduced laser intensity verifies the role of the waveguide effect. [ABSTRACT FROM AUTHOR]

Both random laser and multimode band-edge laser have been found in cholesteric liquid crystals (CLCs). In this work, the laser emission in CLC with negative dielectric anisotropy under electric fields with different frequencies is investigated. Awide multi-wavelength lasing is achieved via the formation of multiple domains induced by low-frequency alternating current (AC) in the CLC system. The photonic bandgap with aweak reflection for aspecific band can also be observed in the multiple domains structure. Furthermore, two types of liquid crystal hosts with different birefringences are used to obtain different lasing cover ranges. The range of the multi-wavelength lasing is within the CLC bandgap and positively correlated to the bandwidth of the bandgap. In addition, ahigh-frequency AC or direct current (DC) can switch it to aband-edge laser based on the regular planar helical structure. The wide range switchable multi-wavelength laser may provide various applications, such as sensing and communication. [ABSTRACT FROM AUTHOR]

In contrast to conventional anti‐counterfeiting technologies, which are susceptible to decryption and exhibit limited effectiveness, the utilization of light to dynamically configure soft materials in a fully reversible and programmable manner not only enhances data security but also improves anti‐counterfeiting performance. However, achieving precise control over reflection structural colors and laser wavelengths within a broad dynamic range remains a challenge. In this study, a UV‐responsive soft helical superstructure is established by combining a photochromic compound with chiral liquid crystals (LCs). By manipulating the Bragg reflection angle, structural reflection colors ranging from red to cyan are successfully achieved. The introduction of an anti‐counterfeiting technique that embeds diverse micro‐structures provides features such as color adjustability, erasability, and angle‐dependent stability. Using the unique properties of this soft helical superstructure, the implementation of a wavelength‐tunable LC bandgap laser through optically reconfigurable Förster resonance energy transfer processes is showcased. Furthermore, a straightforward prototype information encoder is developed to mimic the processes of information encoding and decoding, bypassing the need for complex algorithm design. This research underscores the practicality of LC helical soft systems, emphasizing their distinctive responsiveness to light and their applicability in optical programming photonics. [ABSTRACT FROM AUTHOR]