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Volumetric light-shaping polymer-dispersed liquid crystal films for mini-LED backlights
摘要： Volumetric light-shaping polymer-dispersed liquid crystal (PDLC) films for mini-LED backlit liquid crystal displays (LCDs) are proposed and experimentally demonstrated. With proper material engineering and good vertical alignment of liquid crystals, passive PDLC films with angle-selective scattering properties can be achieved. Such films only respond to angles rather than spatial locations. By directly adhering the PDLC films onto a LED, angular intensity distribution of light can be tailored from Lambertian-like to batwing-like. Further simulation shows that by engineering the angular distribution, a fewer number of LEDs or equivalently a shorter light-spreading distance should be required to maintain good uniformity. Such a PDLC film would find widespread applications in emerging mini-LED backlit LCDs and shed light on designing other light-shaping films in the future.
关键词： Polymer-dispersed liquid crystals,volumetric diffusers,angle-dependent scattering,mini-LED backlights
更新于2025-09-23 15:21:01
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Phototuning Energy Transfer in Self-Organized Luminescent Helical Superstructures for Photonic Applications
摘要： Stimuli-triggered changes in the emission color of functional materials are in demand for a variety of potential applications. Herein, a strategy to reversibly phototune fluorescence color in cholesteric liquid crystal (CLC) with self-organized luminescent helical superstructure via fluorescence resonance energy transfer (FRET) is developed. This dynamic FRET system is constructed by doping with 1,2-dithienyldicyanoethene-based chiral fluorescent photoswitch (switch 7) as an acceptor and a conventional coumarin dye C6 as a donor into a nematic liquid crystal (LC) host. The efficient energy transfer from C6 to switch 7 in the LC media, which is evidenced by both of emission color shift and enhanced circularly polarized luminescence, can be modulated on the basis of reversible trans–cis photoisomerization of switch 7 upon visible/UV light irradiations, leading to the emission color change from orange to green. Noteworthily, the FRET efficiency can be significantly improved when CLCs are confined in the polymer microtubes. Preliminary demonstrations of the LC film and LC microtubes array for information display and encryption with ease of electrical operation between planar, homeotropic, and focal conic states or light manipulation are described.
关键词： cholesteric liquid crystals,optically and electrically tunable fluorescence patterns,displaying and encrypting,phototuning energy transfer,polymer microtubes
更新于2025-09-23 15:21:01
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Chirped polarization volume grating for wide FOV and higha??efficiency waveguidea??based AR displays
摘要： We demonstrate a reflective chirped polarization volume grating as a strong contender for wide field-of-view augmented reality display systems. By introducing gradient pitch along the beam propagation direction, the angular bandwidth extends dramatically from 18(cid:1) to 54(cid:1) while keeping over 80% average efficiency and 95% peak efficiency.
关键词： liquid crystals,augmented reality,polarization volume grating,gradient pitch structure
更新于2025-09-23 15:21:01
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Dielectric and electro-optic studies of a ferroelectric liquid crystal dispersed with different sizes of silica nanoparticles
摘要： The impact of the size of silica nanoparticles (SNPs) on the properties of ferroelectric liquid crystals (KCFLC 10R) has been investigated by electro-optical and dielectric techniques. We have found that the doping of silica nanoparticles in the host ferroelectric liquid crystal strongly affects the various properties of doped systems. Doping of silica nanoparticles shows a small decrease in spontaneous polarisation and faster switching time. An improvement in permittivity and conductivity with the temperature at a constant frequency was also noticed after dispersion. This dependence is stronger for large size particles (,40 nm) and weaker for small size particles (~12 nm). The Goldstone mode (GM) shifts towards the higher relaxation frequency. These results would be useful to manufacture better optical and electronic devices for display, switching and beam steering applications.
关键词： relaxation frequency,Ferroelectric liquid crystals,spontaneous polarisation,silica nanoparticles,goldstone mode,electro-optical,switching time
更新于2025-09-23 15:21:01
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Nonlinear Optics || Molecular Origin of the Nonlinear Optical Response
摘要： In Chapter 3, we presented a general quantum-mechanical theory of the nonlinear optical susceptibility. This calculation was based on time-dependent perturbation theory and led to explicit predictions for the complete frequency dependence of the linear and nonlinear optical susceptibilities. Unfortunately, however, these quantum-mechanical expressions are typically far too complicated to be of use for practical calculations. In this chapter we review some of the simpler approaches that have been implemented to develop an understanding of the nonlinear optical characteristics of various materials. Many of these approaches are based on understanding the optical properties at the molecular level. We also present brief descriptions of the nonlinear optical characteristics of conjugated polymers, chiral molecules, and liquid crystals.
关键词： chiral molecules,nonlinear optical susceptibility,liquid crystals,quantum-mechanical theory,conjugated polymers,time-dependent perturbation theory
更新于2025-09-23 15:21:01
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Square and Hexagonal Columnar Liquid Crystals Confined in Square and Triangular Pores
摘要： Columnar liquid crystals confined in cylindrical pores are known to orient perpendicular to the pore axis, although for potential nanoelectronic applications they would need to be aligned axially. The X-ray diffraction study reveals that while in all three compounds examined, the columns arrange in concentric circles in circular pores, axial alignment is indeed achieved for the hexagonal phase of a discotic hexa-peri-hexabenzocoronene in “triangular pores,” and for the square phase of a T-shaped amphiphile in “square pores.” For the third compound, a carbazole dendron with very soft hexagonal columns, a new three-circle configuration is observed by atomic force microscopy (AFM) in triangular pores. The complex structure of domain walls in columnar liquid crystals is thus seen for the first time on the level of individual columns. A simple estimation of free energies confirms that it is the distortion of polygonal columnar lattice that prevents axial orientation in circular pores. The model also explains the appearance of the three-circle arrangement of soft columns.
关键词： columnar liquid crystals,confinement,axial orientation,triangular pores,square pores
更新于2025-09-23 15:21:01
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Phase transitions in nanofilms of polar smectic liquid crystals with multilayer periodicity
摘要： Optical investigations and calculation of structures were performed on ?lms of liquid crystal with the sequence of phase transitions in the bulk sample SmC??SmC??SmA?I. We investigated freestanding nano?lms with number of smectic layers from 2 to 6 with thickness commensurate, smaller, or greater than the period of SmC?d4 phases of the bulk sample. The number of phase transitions increases as the ?lm thickness increases. Under temperature change the transitions occur with conservation as well as with change of the direction of ?lm polarization with respect to the molecular tilt plane. In thick ?lms at high temperature the ?lm can be switched by electric ?eld from the state with longitudinal (parallel to the molecular tilt plane) into a state with transverse (perpendicular to the molecular tilt plane) electric polarization. In the framework of Landau theory of phase transitions, structures and phase transitions in the bulk sample and in nano?lms were calculated; values of interlayer interactions were estimated. The molecular structure was assumed to be planar with different sequences of synclinic and anticlinic orderings in nearest layers. The results of calculations are in good agreement with experiment.
关键词： multilayer periodicity,Landau theory,phase transitions,nano?lms,polar smectic liquid crystals
更新于2025-09-23 15:21:01
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Soft Materials Driven by Photothermal Effect and Their Applications
摘要： We are surrounded by soft materials. Most organs of the human body are made of soft materials. One defining characteristic of soft materials is that they can be readily deformed by external stimuli and stress. Even the thermal energy available at room temperature is sufficient to cause significant deformation in soft materials. de Gennes in his 1991 Nobel lecture emphasized “flexibility” as a defining characteristic of soft materials. Colloids, polymers, liquid crystals (LCs), gels, and biological materials are categorized as soft materials. Being pervasive in nature, soft materials have been a source of inspiration for scientists and engineers for the design and fabrication of stimuli‐responsive smart materials and systems for scientific investigations to understand the basic principles and technological application in devices and health care. Accordingly, a wide variety of engineered soft materials have been developed, which play a crucial role in modern technology. Soft nanotechnology, soft robotics, and soft lithography are examples that reflect the far‐reaching implications of soft materials in biology and engineering. Soft materials constitute one of the most stimulating interdisciplinary frontiers of modern science and are built on diverse experimental and theoretical foundations. Although soft materials in neat state have found a wide range of applications, fabrication of composites of soft materials by integrating other functional materials has recently become a common practice to realize advanced and tunable materials with enhanced properties for high‐tech applications. Incorporation of photothermal agents into the matrices of soft materials is one such emerging approach.
关键词： nanocomposites,soft materials,liquid crystals,photothermal therapy,polymers,gels,photothermal effect,actuators,drug delivery
更新于2025-09-23 15:21:01
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photoinduced Liquid Crystal Domain Engineering for Optical Field Control
摘要： Liquid crystals (LCs) have attracted considerable attention due to their pronounced high optical anisotropy/transparency over a wide electromagnetic spectrum, high sensibility to various external field stimuli (such as electric/magnetic field, light irradiation, and heat) and strong capability for matter and electromagnetic field interactions. Thanks to their large birefringence and reconfigurable director (i.e. local optical axis) orientation, LCs have become one of the most attractive candidates for making optical devices requiring versatile functionalities. Particularly, liquid crystal display (LCD) holds a dominant position in the flat panel display market nowadays. Essentially, they are composed of a huge number of separate light intensity modulators in the visible range. In addition to amplitude, LCs can freely manipulate other spatial degrees of light, such as polarization and phase. Through specifical designing of the director distribution of LC domains, one could arbitrarily manipulate the optical field. Optical field control is a key requirement for optics and photonics. Structured light, also known as shaped light or tailored light, is a light beam that has customized intensity, polarization, and phase. Recently, specific beams including vortex beams, vector beams (VBs), and Airy beams have been studied intensively due to their fantastic properties and diverse applications in optical trapping, laser processing, high‐resolution imaging, etc. Generally, these beams can be directly generated from Gaussian beams by spatially manipulating the amplitude or phase of light. Such manipulations could be accomplished by lens or plates with specific curvature radius, photoresist masks, or metasurfaces with delicately designed structures. However, their optical characteristics are static once the respective device is fabricated, which severely restricts corresponding applications. Thanks to the electro‐optical tunability of LCs, structured LC domains make these devices dynamic and more efficient.
关键词： vector beams,Airy beams,photoalignment,vortex beams,optical field control,structured light,Liquid crystals
更新于2025-09-23 15:21:01
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Study on the morphologies and electro-optical properties of cyano-phenyl-ester liquid crystals/polymer composite films prepared by a stepwise polymerisation
摘要： In this work, a series of liquid crystal molecules containing cyano-phenyl-ester was designed and synthesised. Subsequently, a novel cyano-phenyl-ester liquid crystals (CPE-LCs) with a wide temperature range from ?30°C to 96.4°C were developed by mixturing these liquid crystal compositions. Then as the host materials, the CPE-LCs were used for preparing polymer-dispersed and polymer-stabilised cholesteric liquid crystals (PD&SCLC) composite ?lms by a stepwise polymerisation. The morphologies and electro-optical properties of the as-made composite ?lms were systematically investigated through varying the acrylate liquid crystalline polymerisable monomers content, chiral doping R1011 content, applied electric ?eld intensity and polymerisation time. Indeed, the formation of homeotropically aligned anisotropic polymer networks (HAAPNs) enabled to reduce the driving voltage of PD&SCLC from 86.6 V to 22.2 V with a reasonable contrast ratio. This work provides a new method to optimise PD&SCLC composite ?lms in terms of the host liquid crystals.
关键词： electro-optical properties,polymer-dispersed and polymer-stabilised cholesteric liquid crystals,network morphologies,Cyano-phenyl-ester liquid crystals,stepwise polymerisation
更新于2025-09-23 15:19:57