Electrooptical Effects Due to the Uniform Distortion of Nematic Liquid Crystals

Blinov, L. M.; Chigrinov, Vladimir G.

doi:10.1007/978-1-4612-2692-5_4

Cited by 8 publications

(3 citation statements)

References 206 publications

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“…When the incident light polarization is at an angle ( θ ) with respect to the LC director, the effective refractive index n eff for the light can be expressed as

[ 83 ]. When a voltage higher than the threshold voltage [ 87 ] is applied to the electrodes, the angle θ will change, leading to n eff varying from n e to n o . Figure 8 illustrates the operation principle of a nematic LC lens.…”

Section: Optical Depth Scanning By Tuning the Optical Power Of The Op...mentioning

confidence: 99%

Technologies for depth scanning in miniature optical imaging systems [Invited]

Liu,

Zhang,

2023

Biomed. Opt. Express

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Biomedical optical imaging has found numerous clinical and research applications. For achieving 3D imaging, depth scanning presents the most significant challenge, particularly in miniature imaging devices. This paper reviews the state-of-art technologies for depth scanning in miniature optical imaging systems, which include two general approaches: 1) physically shifting part of or the entire imaging device to allow imaging at different depths and 2) optically changing the focus of the imaging optics. We mainly focus on the second group of methods, introducing a wide variety of tunable microlenses, covering the underlying physics, actuation mechanisms, and imaging performance. Representative applications in clinical and neuroscience research are briefly presented. Major challenges and future perspectives of depth/focus scanning technologies for biomedical optical imaging are also discussed.

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“…When the incident light polarization is at an angle ( θ ) with respect to the LC director, the effective refractive index n eff for the light can be expressed as

Section: Optical Depth Scanning By Tuning the Optical Power Of The Op...mentioning

confidence: 99%

Technologies for depth scanning in miniature optical imaging systems [Invited]

Liu,

Zhang,

2023

Biomed. Opt. Express

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“…Oriented LC molecules determine the microscopic structure of the polymer-LC interface which becomes compatible with their alignment. Although the use of one alignment layer can normally produce only homogeneously aligned cells, we have successfully prepared twisted nematic devices [4] by adding a chiral dopant to induce a twisted structure.…”

Section: Composite Films Of Liquid Crystalsmentioning

confidence: 99%

Phase separated composite films of liquid crystals

1999

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Phase separation of liquid crystals from a solution with polymers has long been studied and used to prepare polymer stabilized and polymer dispersed structures. They are formed by spatially isotropic phase separation. A new mode, in which the phase separation proceeds anisotropically, has recently been discovered. Known as phase separated composite films (PSCOF), the resultant structures are made of adjacent parallel layers of liquid crystal and solidified polymer. PSCOFs have been made with nematic, ferroelectric (FLC), and antiferroelectric (AFLC) liquid crystals. Liquid crystals in PSCOFs exhibit electro-optical properties not observed in devices prepared by conventional methods, polymer dispersion, or polymer stabilization methods. Devices incorporating FLCs possess grey scale and switch 100 times faster at low fields than conventional surface stabilized devices. This method makes it possible to prepare very flexible devices and devices with liquid crystal film thickness comparable to optical wavelengths with great ease.

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“…and reduced light lost from reflectivity which are all highly desirable properties for optical screens. 7,24,29 Along with the benefits of multipurpose materials, PSCLCs require less power and have lower costs than other similar optical materials contributing to commercial and economic interests in developing PSCLC materials. 2,[15][16] The current drawbacks and major disadvantages of PSCLC materials are their relatively long relaxation times and the lack of knowledge about how photopolymerization kinetics, CLCpolymer structure, and CLC-polymer network interactions affect PSCLC electro-optical properties.…”

Section: Liquid Crystal Structurementioning

confidence: 99%

The effect of morpholine and polymer network structure on electro-optical properties of polymer stabilized cholesteric liquid crystals

Lippert¹

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Polymer stabilized cholesteric liquid crystals (PSCLCs) provide many advantages over other electro-optical materials. The unique helical structure of the cholesteric liquid crystal (CLC) creates a natural gradient for light interacting across each CLC domain layer. Not only does the CLC helical structure greatly increase the bandwidth tuning and broadening range, it also allows CLCs to act as a polarizer, notch filter, reflector, and optical rotator all in one material. However, while many novel PSCLC materials have been created, little is understood about how complex initial system interactions affect final electro-optical (e-o) properties. 1,2 In this work, the principal variables affecting PSCLC blue shift electro-optical behavior have been determined through structural analysis and measurement of electro-optical properties. Typical PSCLC materials must meet both formulation and photopolymerization processing requirements to display blue shift e-o properties. Threshold photoinitiator concentrations (0.5-1.5 wt%) and morpholine containing group concentrations (0.25-1.0 wt%) were both shown to be primary factors, along with sufficient UV exposure time (10-30 min) and light intensity (500 mW/cm 2 , 365 nm), for PSCLC blue shift bandwidth tuning/broadening to occur. Morpholine was initially identified as a component of photoinitators Irgacure 369 and 907 and was proven to increase PSCLC ion density altering LC-polymer network interactions with several proposed theories included later in this work. The use of an appropriate morpholine containing LC monomer to directly incorporate morpholine into the LC-polymer network was shown to greatly improve PSCLC sample stability. Through the results of this research we successfully induced blue shift e-o behavior in a previous red shift only PSCLC using only 30% of the UV exposure that a model PSCLC blue shift sample required while extending the blue shift broadening range over threefold (from 75 nm to 250 nm). The fundamental understanding and design of PSCLC iv systems described herein serves as a starting point for engineering PSCLC materials with specific and desirable electro-optical properties. v PUBLIC ABSTRACT Society depends on electronic screens and devices to interact with the vast amounts of daily entertainment and information. Liquid crystals (LCs), a type of material that shares properties of both liquids and solids, have played a significant role in current technologies like TV, smartphone, and computer screens. LCs unique structural and optical properties allow them to be used like an electronic door, opening and shutting at precise intervals selectively allowing light through to display pictures and colors on electronic screens. Recently it has been shown that helical structured cholesteric liquid crystals (CLC), when combined with a stabilizing polymer network, can be used to make improved optical materials. However, while many novel polymer stabilized cholesteric liquid crystal (PSCLC) materials have been created, little is understood about how complex ini...

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Electrooptical Effects Due to the Uniform Distortion of Nematic Liquid Crystals

Cited by 8 publications

References 206 publications

Technologies for depth scanning in miniature optical imaging systems [Invited]

Technologies for depth scanning in miniature optical imaging systems [Invited]

Phase separated composite films of liquid crystals

The effect of morpholine and polymer network structure on electro-optical properties of polymer stabilized cholesteric liquid crystals

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