Dependence Of Diffraction Efficiency Research Articles

Dynamic Holographic Display Based on Perovskite Nanocrystal Doped Liquid Crystal Film

Holography can produce the most real three-dimensional (3D) image, and is considered as the ultimate 3D display technology. However, compared with other display technologies, it has not been practically available in video display so far due to low refresh rate. To realize dynamic holographic display, photosensitive material doped liquid crystal (LC) has been discovered and deeply investigated because of superior photorefractive and photoelectric properties. In this work, we present a dynamic holographic display using LC film doped with perovskite (CsPbBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) nanocrystal (NC) as the photorefractive material. The dependence of diffraction efficiency and response time on doping concentration, recording beam power and applied voltage are investigated. A maximum diffraction efficiency of 18% has been achieved under a low electric field intensity of 0.45 V/μm and the shortest build-up time of grating is 5.5 ms. The system can realize a video display with 60 Hz refresh rate in red, green and blue colors, which demonstrates the feasibility of applying perovskite NC doped LC film in dynamic holographic display.

APPLICATION OF OPTICAL DIFFRACTOMETRY FOR THE ERROR MONITORING OF MANUFACTURING OF PRECISION OPTICAL ELEMENTS

The work is devoted to an experimental study of the effectiveness of the method for measuring errors in manufacturing of computer-generated synthesized holograms using specialized marks. Each mark represents two aligned diffraction gratings with the same duty cycle and period, the first of which is formed before writing, and the second is formed in the process of forming the structure of the hologram. To determine the writing error, the method of optical diffractometry was used. The results of an experimental study of dependence of diffraction efficiency of the mark on the mutual displacement of parts of the microgratings are presented. The error manufacturing of a synthesized hologram arising during long-term writing of a diffractive optical element has been simulated experimentally.

85‐5: Late‐News‐Paper: Real Time Dynamic Holographic Display Based on Perovskite Doped Liquid Crystal

Holographic display, which can completely reconstruct phase and amplitude information, is considered as an ideal true three‐dimensional display technology. In this work, liquid crystal doped with perovskite (CsPbBr3) works as the photorefractive material and forms diffraction grating under the interference light beams. The dependences of diffraction efficiency and response time on doping concentration, recording beam power and applied voltage are investigated. A maximum first‐order diffraction efficiency of 18% has been achieved under a low electric field intensity of ~0.5 V/μm and the shortest grating build up time is as low as 5.5 ms. The system can realize a real‐time dynamic display with 60 Hz refresh rate.

Analysis of diffraction efficiency of phase gratings in dependence of duty cycle and depth

The analysis of dependence of diffraction efficiency on duty cycle and modulation depth of phase gratings with rectangular and Gaussian profile was performed by means of specially designed program. An Angular Spectrum method applied for monochromatic light propagation in far field through phase grating was used for calculation of diffraction efficiency of gratings. Diffraction efficiency maps of 0-5th diffraction orders were obtained for different grating profiles. It is shown that changing the duty cycle of grating makes it possible to tune smoothly the diffraction efficiency and to redirect the light intensity in required orders.

Magnetically tunable optical diffraction gratings based on a ferromagnetic liquid crystal.

Transmission optical diffraction gratings composed of periodic slices of a ferromagnetic liquid crystal and a conventional photoresist polymer are demonstrated. Dependence of diffraction efficiencies of various diffraction orders on an in-plane external magnetic field is investigated. It is shown that diffraction properties can be effectively tuned by magnetic fields as low as a few mT. The tuning mechanism is explained in the framework of a simple empirical model and also by numerical simulations based on the rigorous coupled wave analysis (RCWA). The obtained results provide a proof of principle of operation of magnetically tunable liquid crystalline diffractive optical elements applicable in contactless schemes for control of optical signals.

ВЛИЯНИЕ ПРИРОДЫ ЗАМЕСТИТЕЛЯ В АЗОБЕНЗОЛЬНЫХ ХРОМОФОРАХ НА ДИФРАКЦИОННУЮ ЭФФЕКТИВНОСТЬ ПОЛЯРИЗАЦИОННЫХ ГОЛОГРАММ

The films of polymeric composites containing monomers of azobenzene dyes or azobenzene lateral groups chemically bonded to the main polymer chain demonstrate photoactive properties, and can be used in electrooptical light modulators and in recording media (RM) for polarization holography. Photoinduced optical anisotropy (PIA) appears under influence of linearly polarized light caused by the processes of trans-cis-izomerization of the azobenzene groups. This process is determining for application of the considered materials as RM for polarization holography. The films of polymeric polarization sensitive media based on a copolymer of styrene with nonyl methacrylate doped with azobenzene-type dyes with different electron-acceptor substituents are obtained in this work. In the films of copolymer the holograms of the plane wave front were registered for parallel and orthogonal orientations of polarization vectors of the object and reference light beams. Their photoelectrophysical, in particular photodielectric, and information properties are investigated. It was established, that when the mutual orientation of the recording beams changes from the orthogonal to parallel orientation the diffraction efficiency of the holograms increases in the case of using azo dye with the maximum number of auxochromic substituents in the molecule. The effect of the diffraction efficiency dependence on the chromophores structure is connected with the deepening of dye color. The photo-induced optical anisotropy in the films appears due to a change of the concentration ratio of trans- and cis-isomers of azobenzene dye fragments. This conclusion is confirmed by the photodielectric measurements data, namely, by the negative sign of the photodielectric effect, observed experimentally in the investigated thin film structures. It was shown, that investigated compositions can be used as information media for polarization holography.

Modulation spectra of volume holograms recorded in additively colored fluorite crystals

Additively colored fluorite crystals are of considerable interest as a holographic recording medium. Due to very high stability as well as potentially large refractive index modulation, its possible to use holograms recorded in these crystals as high quality diffractive elements and photonic-crystalline structures. Therefore, it is important to be able to correctly and accurately analyze such structures. Spectral dependencies of absorption coefficient and refractive index profiles are the most precious characteristics in this regard. Unfortunately, they are also the most elusive ones. In this study the required parameters were obtained by a method based on the analysis of selectivity hypercontours (combined spectral and angular dependencies of diffraction efficiency) using the Kogelnik’s coupled wave theory in wide optical spectral range. Hologram profile was reconstructed from first three spatial harmonics. The results were crosschecked with monochromatic analysis to prove the validity of proposed technique.

The excitation and detection of a leaky surface electromagnetic wave on a high-index dielectric grating in a prism-coupler geometry

A periodically corrugated interface between vacuum and a high-index dielectric medium supports a p-polarized leaky surface electromagnetic wave whose sagittal plane is perpendicular to the generators of the interface. This wave is bound to the surface in the vacuum region, but radiates into the high-index dielectric medium. We study the excitation of this wave by p-polarized light incident from a prism on whose planar base the highindex dielectric medium in the form of a film is bonded. The unilluminated surface of the film is periodically corrugated, and is in contact with vacuum. Peaks and dips in the dependence of several low-order diffraction efficiencies on the angle of incidence (Wood anomalies) are the signatures of the excitation of the surface wave.

Molecular design of azo-carbazole monolithic dyes for updatable full-color holograms

For the use of updatable full-color holography in practical applications, azo-carbazole (ACzE) monolithic dyes dispersed in poly(methyl methacrylate) (PMMA) films with high diffraction efficiency, write/delete capabilities and transparency are of extreme importance. We synthesized seven types of novel ACzE monolithic dyes and examined the influence of substituents introduced in the para position of the phenyl ring and the distinct strength of the substituents (NO2: NACzE, CN: CACzE, CH3CO: AACzE, F: FACzE, CH3O: MACzE, OH: HACzE and NH2: AmACzE) on the phenyl ring of the ACzEs. Spectroscopic and holographic optical properties, including absorption coefficient α, wavelength dependence of diffraction efficiency η, response time τ, the thickness of the recorded gratings d, the Bragg angle Δϑ and the Q-factor, required for the optimization of updatable full-color holograms were investigated. On the basis of the spectroscopic and holographic optical results, the appropriate writing/reading beams were determined as follows: 561/>600 nm for NACzE, 532/>560 nm for CACzE (and AACzE), 491/>530 nm for MACzE (and HACzE). According to the spectroscopic and holographic optical results, we propose here an insight designed to allow updatable full-color holography using ACzEs, and demonstrate a multi-color hologram in MACzE/PMMA. A holographic system that uses low-cost materials to capture and rewrite full-colour 3D images has been developed by Japanese researchers. Naoto Tsutsumi from the Kyoto Institute of Technology and co-workers recently developed a red-coloured hologram based on an azo-carbazole dye that can be aligned, similar to a liquid crystal, using polarized light. Now, to tune the colour output, the team has modified phenyl rings on the original dye with a series of small, electron-donating and -withdrawing chemical groups. Spectroscopic and optical trials revealed that the colours from the functionalized dyes depend on the laser wavelengths used to write and read the hologram. The researchers exploited this behaviour with a system that combines red, green and blue holograms together in an updateable, full-colour video display. We report novel azo-carbazoles that can be applied to updatable full-color holography. We introduced a molecular design concept of updatable full-color holographic systems based on spectroscopic and optical characteristics. Taking advantage of characteristics of the designed azo-carbazoles, updatable red, yellow and green holograms can be recorded, which enabled us monochromic hologram as well as full-color hologram in the future.

Low-Toxicity Photopolymer for Reflection Holography.

A novel composition for a low-toxicity, water-soluble, holographic photopolymer capable of recording bright reflection gratings with diffraction efficiency of up to 50% is reported. The unique combination of two chemical components, namely, a chain transfer agent and a free radical scavenger, is reported to enhance the holographic recording ability of a diacetone acrylamide (DA)-based photopolymer in reflection mode by 3-fold. Characterization of the dependence of diffraction efficiency of the reflection gratings on spatial frequency, recording intensity, exposure energy, and recording wavelength has been carried out for the new low-toxicity material. The use of UV postexposure as a method of improving the stability of the photopolymer-based reflection holograms is reported. The ability of the modified DA photopolymer to record bright Denisyuk holograms which are viewable in different lighting conditions is demonstrated.

Photoinduced phenomena in amorphous As4S3Se3–Sn films

We investigate the kinetics of photodarkening and recording of holographic diffraction gratings in amorphous As4S3Se3 thin-film structures doped with tin (Sn) in concentrations of 0–10 at %. It is established that an increase in the Sn concentration leads to a decrease in the photodarkening rate and degree. The photodarkening kinetics is approximated by a stretched exponential function. It is found that an increase in the Sn concentration leads to a decrease in the transmission (photodarkening) variation in the investigated As4S3Se3–Sn films. It is determined that, in the recording of holographic diffraction gratings at a Sn concentration of 3–8 at %, the As4S3Se3–Sn films exhibit the maximum sensitivity and diffraction efficiency of the recorded gratings. It is shown that the dependence of diffraction efficiency on the As4S3Se3 film thickness has the maximum at a film thickness of 4 µm.

Investigation of structural features of As2S3–Se multilayer nanostructure by Raman spectroscopy

The focus of this research is on the investigation of structural changes in the As2S3–Se multilayer nanostructure and on the examination of a relative contribution of As2S3 and Se layers to nanostructuring by measuring the Raman spectra. The formation of the As2S3-Se nanostructure by an alternate As2S3 and Se layers deposition was applied. The diffraction efficiency dependence on the exposure of a CW DPSS laser were monitored in a transmission mode of the1st order diffracted beam intensity and measured in real-time at the normal incidence of the laser diode beam (λ = 650 nm). From the comparison of these dependences for a set of samples we have chosen the multilayer nanostructure As2S3–Se with optimal recording properties meaning maximum both the value and the rate of diffraction efficiency. Our results are found to be of practical interest as they allow a significant improvement of the diffraction efficiency of the directly recorded relief gratings.

P‐120: Temperature Dependence of Dynamic Holographic Displays using Doped Liquid Crystals

The temperature dependence of diffraction efficiency and response time in two holographic systems using doped liquid crystals (LC) is investigated. For dye‐doped LCs, the response time is generally robust to temperature variation but the diffraction efficiency is temperature‐sensitive; whereas, the QD‐doped LC remains robust for both characteristics around room temperature.

OPC Model Calibration Accuracy Improvement by Using Mask 3D Model

Low k1 and high NA lithography of critical layers require advanced resolution enhancement techniques for masks on large designs such as scattering bars, complicated mask edge placement and segmentation, etc. When mask feature sizes are comparable to or less than the exposure wavelength, the thin mask model (Kirchhoff) has been proven inadequate. It has been well known that mask 3D effects lead to image contrast loss, feature-dependent best focus, dependence of diffraction efficiency on illumination, etc. Mask transmission obtained with a rigorous solver of Maxwell Equations could catch these effects but running time is too slow and impractical for large chips OPC. HHA (Hybrid Hopkins Abbe) and DDM (Domain Decomposition Method) offer a fast and sufficiently accurate mask 3D OPC model solution. In this paper, we set up mask 3D model using HHA and DDM method for 28nm clear-field critical layers. We compare 3D model experimental results with thin mask 2D Kirchhoff model. The results shows mask 3D OPC model calibration get better model fitting error than 2D OPC model, also the improvement of model calibration results on model verification structures and on real design structures was realized by the use of 3D HHA and DDM models. The comparison result also shows process window data calibration accuracy increased by the mask 3D model.

Surface relief grating recording in azo polymer films

In this work holographic recording of surface relief grating in organic Poly(Disperse Red 1 – methacrylate) thin films was studied. In this compound azo dye is chemically bonded to monomers making mass transport very efficient in the presence of optical field gradient. Sample preparation was performed using different solvents and coating methods. In the obtained samples holographic recording was performed by solid-state diode pump laser with 532 nm wavelength. Polarization grating and surface relief grating formation was studied by diode laser with 660 nm wavelength. Diffraction efficiency's dependence on read-out laser beam polarization state was investigated. The depth of surface relief grating was measured by AFM and studied in dependence on recording beam intensity, exposure and thickness of the sample.

Temperature dependence of anisotropic diffraction in holographic polymer-dispersed liquid crystal memory

Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC.

Paper No P27: Features of Polarization Diffraction Gratings Switching Under the Influence of Bipolar Electric Pulses

AbstractThe diffraction efficiency dynamics of planar‐planar periodic liquid crystal structure under the influence of quasistatic (1 kHz), as well as pulse electric fields is studied. In quasistatic control mode ±1 diffraction orders are observed in the voltage absence, and at the electric field switching on the diffraction disappears, that is, only zero order is observed. In contrast to the quasistatic control mode, under the influence of single bipolar electric pulses the increase in diffraction efficiency is observed in ±1 order, and at that the zero order is absent. The dependence of diffraction efficiency on the control pulses repetition frequency and amplitude is also studied. The results of these investigations can find application in displays development.

Polarization-sensitive diffractive optical elements fabricated in BR films with femtosecond laser

Multi-photon product (F540-state) of bacteriorhodopsin (BR) polymeric films excited by femtosecond laser shows permanently photoinduced birefringence and dichroism. Based on this property, polarization-sensitive diffractive optical elements (PDOEs), e.g., gratings, two-dimensional optical lattice, Bessel zone plate, were firstly fabricated and investigated in BR films by femtosecond laser multi-beam interference with rotationally symmetric pyramid lenses. These fabricated PDOEs are completely stable at room temperature. The dependence of diffraction efficiency on the incident polarization state was measured. The micro-structures of PDOEs were observed under polarization microscope, and the selective readout diffraction patterns from the polarization-multiplexed PDOEs were demonstrated.

Formation of temperature dependable holographic memory using holographic polymer-dispersed liquid crystal

Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization controllable optical devices, such as the holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) that the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is discussed with two types of LC composites comprised of isotropic and LC diacrylate monomers. The holographic memory formed by the LC and LC diacrylate monomer performs precise reconstruction of the context information for ORGAs at high temperatures more than 150°C.

Modeling adapted to manufacturing of holographic super Gaussian gratings

A few holographic metallic (gold and silver) gratings with maximum diffraction efficiency (DE) in the 700 to 1100 nm wavelength range were designed. These designed diffraction gratings can be attractive for stretching and compressing pulses in chirped pulse amplification (CPA) technology. They were optimized for transverse magnetic polarized light in the first order (littrow mount). KPP1206 photoresist was used to model the final pattern on photoresist thin film. To obtain super Gaussian profiles, approximately identical exposure energy density intervals were used for optimizing grating profile. The optimized gold and silver gratings were compared in terms of DE, bandwidth and incidence angle range. Dependence of DE on the depth and duty cycle of super Gaussian gold and silver gratings showed that the silver grating had higher DE than the gold grating in 1064 nm. Fabricated silver grating based on modeling results had good agreement with experimental results.