Electro-optical Characteristics of a Liquid Crystal Lens with Polymer Network

We study a tunable-focus lens in which the key element is a gradientpolymer-stabilized liquid crystal (G-PSLC) structure. In this paper, we further develop the theoretical model [1, 2] that describes the dependence of the G-PSLC lens’ focal length on the applied voltage and presents a theoretical study of lens aberrations. According to Fermat’s principle, we minimize the optical path of a test light beam and calculate the angles of a ray exiting from the cell. Using these results, the lateral and longitudinal aberrations are estimated. The obtained results can be used to optimize the G-PSLC lenses.У данiй роботi вдосконалено теоретичну модель лiнзи [1, 2], утвореної в нематичному рiдкокристалiчному кристалi в процесi фотополiмеризацiї в неоднорiдному свiтловому полi гаусового пучка. Знайдено чисельно кут переорiєнтацiї директора нематичного рiдкого кристала та фокусну вiдстань лiнзи в залежностi вiд величини напруги прикладеної до нематичної комiрки. Використовуючи принцип Ферма, мiнiмiзовано оптичний шлях свiтлового пучка, що проходить крiзь утворену лiнзу. Отримано напрямок поширення свiтла на виходi з комiрки, що дозволило оцiнити поздовжню та поперечну аберацiї рiдкокристалiчної нематичної лiнзи. Зi збiльшенням прикладеної напруги, величина аберацiй зменшується. Отриманi в статтi результати дозволяють оптимiзувати якiсть зображення, що утворює лiнза

Wound analgesia in a patient with hemophilia in a highly traumatic operation

Given a number of limitations on the use of perioperative analgesia in patients with hemophilia, wound analgesia may be one of the components of multimodal analgesia in this category of patients. The aim of the study was to describe the use of the wound analgesia method in a patient with hemophilia in the case of a clinical case. Materials and methods. A patient with severe hemophilia A underwent postoperative analgesia after total knee replacement (within the first 48 hours) with an extended infusion of local anesthetic (ropivacaine) into the wound. Results. During the first 8 hours, the patient received 20 mg of morphine (with the aid of a device for patient-controlled analgesia), the pain level ranged from 7 to 4 points. Further, there was a sufficient effect (NRS - 2 points), from anesthesia only with ropivacaine, using a system for anesthetizing surgical wounds. Complications and side effects were not noted. Conclusion. The clinical case demonstrates an effective and safe method of prolonged analgesia in patients with hemophilia. Considering encouraging data, further study of wound analgesia in this category of patients is necessary

Multifunctional light beam control device by stimuli-responsive liquid crystal micro-grating structures

There is an increasing need to control light phase with tailored precision via simple means in both fundamental science and industry. One of the best candidates to achieve this goal are electro-optical materials. In this work, a novel technique to modulate the spatial phase profile of a propagating light beam by means of liquid crystals (LC), electro-optically addressed by indium-tin oxide (ITO) grating microstructures, is proposed and experimentally demonstrated. A planar LC cell is assembled between two perpendicularly placed ITO gratings based on microstructured electrodes. By properly selecting only four voltage sources, we modulate the LC-induced phase profile such that non-diffractive Bessel beams, laser stretching, beam steering, and 2D tunable diffraction gratings are generated. In such a way, the proposed LC-tunable component performs as an all-in-one device with unprecedented characteristics and multiple functionalities. The operation voltages are very low and the aperture is large. Moreover, the device operates with a very simple voltage control scheme and it is lightweight and compact. Apart from the demonstrated functionalities, the proposed technique could open further venues of research in optical phase spatial modulation formats based on electro-optical materials.This work was supported by the Comunidad de Madrid and FEDER Program (S2018/NMT-4326), the Ministerio de Economía y Competitividad of Spain (TEC2016-77242-C3-1-R and TEC2016-76021-C2-2-R), the FEDER/Ministerio de Ciencia, Innovación y Universidades and Agencia Estatal de Investigación (RTC2017-6321-1, PID2019-109072RB-C31 and PID2019-107270RB-C21). The authors also acknowledge the support by the Ministry of National Defense of Poland (GBMON/13-995/2018/WAT), Military University of Technology (Grant no. 23-895)

Diffraction efficiency of H-PDLC film with comb-shaped electrodes

А theoretical model of holographic polymer-dispersed liquid crystal film with comb-shaped electrodes has been constructed. The model combines anisotropic coupled-wave theory, Monte-Carlo simulations for director profile within a liquid crystal droplet and statistical averaging with the orientational distribution function for droplet symmetry axes. Influence of the electric field applied along the grating vector on the diffraction efficiency has been studied. The results obtained indicate a way to improve the grating characteristics.Построена теоретическая модель голографической полимер-диспергированной жидкокристаллической (Г-ПДЖК) пленки с гребенчатыми электродами. В модели объединяется анизотропная теория связанных волн, компьютерное моделирование распределения директора внутри жидкокристаллической капли методом Mонте-Карло и статистическое усреднение с функцией распределения осей капель. Исследовано влияние электрического поля, приложенного вдоль вектора решетки, на дифракционную эффективность. Полученные результаты указывают способ улучшения характеристик решетки.Побудовано теоретичну модель голографiчної полiмер-диспергованої рiдкокристалiчної (Г-ПДРК) плiвки з гребiнчастими електродами. У моделi поєднується анiзотропна теорiя зв'язаних хвиль, комп'ютерне моделювання розподiлу директора всерединi рiдкокристалiчної краплi методом Mонте-Карло та статистичне усереднення з функцiєю розподiлу вiсей симетрiї крапель. Дослiджено вплив електричного поля, прикладеного вздовж вектора гратки, на дифракцiйну ефективнiсть. Отриманi результати вказують шлях покращення характеристик гратки

Thermo-optical properties of colloidal solutions of CdTe nanoparticles

Colloidal solutions of CdTe nanoparticles have been prepared by the "electropulse" technique. The diameters of the CdTe nanoparticles range from 5 to 30 nm. The goal of this work is to study the formation and evolution of the induced thermo-refractive index with a long-term goal of forming a thermal lens. An induced thermo-refractive index occurs when the CdTe solutions are irradiated with a strong laser beam. The experimental approach is derived from the Z-scan technique, a technique which is very sensitive to refractive index modulation in a sample. Thermo-optical coefficients, such as the thermal diffusivity, D, the characteristic build-up time of the thermal lens, t(c), and the induced thermo-refractive index can be determined from dynamic Z-scan curves. The thermo-optical coefficients have been determined at different wavelengths, beam powers, and for different nanoparticles sizes. (C) 2005 Elsevier B.V. All rights reserved

Application of a microrheology technique to measure the viscosity of disodium cromoglycate liquid crystal

<p>Although the science of rheology is well established, some important challenges still persist to measure the viscoelastic properties of complex fluids, such as biological solutions and liquid crystals (LC). In this work, we present a method, based on the calculation of the step length of Brownian particles, to measure the effective local viscosity sensed by microscopic objects in the LC host. This approach allowed us to quantify the anisotropy of the viscosity, and it could also be extended to measure the local viscosity in other nonhomogeneous media. We also present a new guided light dark-field microscopy technique that was used to track particles during our experiments.</p