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This paper describes the synthesis, spectroscopic characterization and quantum mechanical calculations of three azo-azomethine dyes. The dyes were synthesized via condensation reaction between 4-(dimethylamino)benzaldehyde and three different 4-aminobenzene azo dyes. Quantum chemical calculations on the optimized molecular geometry and electron densities of the trans (E) and cis (Z) isomers and their vibrational frequencies have been computed by using DFT/B3LYP density-functional theory with 6-311++G(d,p) basis set in vacuo. The thermodynamic parameters such as total electronic energy E (RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed for trans (E) and cis (Z) isomers in order to estimate the ΔEtrans→cis, Δμtrans→cis,ΔHtrans→cis, ΔGtrans→cis and ΔStrans→cis values. After molecular geometry optimization the electronic spectra have been obtained by TD-DFT calculations at same basis set and correlated with the spectra of vapour deposited nanosized films of the dyes. The NBO analysis was performed in order to understand the intramolecular charge transfer and energy of resonance stabilization. Solvatochromism was investigated by UV-VIS spectroscopy in five different organic solvents with increasing polarity. The dynamic photoisomerization experiments have been performed in DMF by pump lasers λ=355nm (mostly E→Z) and λ=491nm (mostly Z→E) in spectral region 300nm - 800nm at equal concentrations and times of illumination in order to investigate the photodynamical trans-cis-trans properties of the CHN and NN chromophore groups of the dyes.

Non-destructive detection of physical or biological activity through statistical processing of speckle patterns on the surface of diffusely reflecting objects is an area of active research. A lot of pointwise intensity-based algorithms have been proposed over the recent years. Efficiency of these algorithms is deteriorated by the signal-dependent speckle data, non-uniform illumination or varying reflectivity across the object, especially when the number of the acquired speckle patterns is limited. Pointwise processing of a sequence of 2D images is also time-consuming. In this paper, we propose to transform the acquired speckle images into binary patterns by using for a sign threshold the mean intensity value estimated at each spatial point from the temporal sequence of intensities at this point. Activity is characterized by the 2D distribution of a temporal polar correlation function estimated at a given time lag from the binary patterns. Processing of synthetic and experimental data confirmed that the algorithm provided correct activity determination with the same accuracy as the temporal normalized correlation function. It is efficient without the necessity to apply normalization at non-uniform distribution of intensity in the illuminating laser beam and offers acceleration of computation.

Analysis of dynamic speckle formed on the surface of diffusely reflecting objects under laser illumination is a non-contact method for inspection of speed of processes. The paper deals with intensity-based implementation of the method that relies on statistical processing of correlated in time sequences of speckle images. A two-dimensional activity map is built for each sequence to visualize regions of different speed on the object surface at a given instant. A great number of images is required to track a process in time. We propose data compression by coarse quantization of the raw speckle data. Efficacy of quantization is analyzed by simulation and experiment for low- and high-contrast speckle patterns with bell-shaped and long-tailed distributions of intensity, respectively. Non-uniform quantization is proposed for long-tailed speckle intensity distributions. Decreasing the bit depth from 8 to 4 causes no change in the probability density function of the activity estimate.

A study of the photoinduced birefringence in nanocomposite thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with gold (Au) nanoparticles (NPs) is presented. The NPs are with a spherical shape and mean size 10 nm. Transmission electron microscopy (TEM) and Dynamic Light Scattering (DLS) analyses of the particles have also been made. Samples were prepared with five different concentrations of the NPs in the azopolymer films varying from 0 (non-doped azopolymer film) to 4 a.u. (1 a.u. = 0.015 wt %). Birefringence was induced by a He-Cd laser with a wavelength 442 nm and measured with probe Diode Pumped Solid State (DPSS) laser at 635 nm. An increase of the photoinduced birefringence in doped azopolymer nanocomposite films compared to samples of undoped azopolymers was observed. The maximal enhancement was achieved for films with 2 a.u. of Au NPs.

Different methods have been employed in order to increase the value of the photoinduced anisotropy in azopolymers and to ensure more effective polarization recording. As recently established, doping photopolymers with nanoparticles allows to achieve near 100% net diffraction efficiency in case of conventional holographic recording. For this reason, we have synthesized novel organic/inorganic composite materials by incorporating 50 nm sized ZnO nanoparticles in series of side-chain azopolymers. We obtained a considerable improvement of the photoresponse in these composite materials compared to the non-doped samples – more than 40% increase of the saturated value of the birefringence (up to Δ n = 0.08) and also reduction of the recording time with about 30%. We also observed an increase of the photoinduced anisotropy after the exposure has been stopped for one of the investigated polymers. The stability of the photoinduced birefringence in all samples suggests applications of these materials as media for polarization holographic data storage and recording of diffractive optical elements with high efficiency and unique polarization properties.

Dynamic laser speckle analysis is non-destructive detection of physical or biological activity through statistical processing of speckle patterns on the surface of diffusely reflecting objects. This method is sensitive to microscopic changes of the surface over time and needs simple optical means. Advances in computers and 2D optical sensors forced development of pointwise algorithms. They rely on acquisition of a temporal sequence of correlated speckle images and generate activity data as a 2D spatial contour map of the estimate of a given statistical parameter. The most widely used pointwise estimates are the intensity-based estimates which compose each map entry from a time sequence of intensity values taken at one and the same pixel in the acquired speckle images. Accuracy of the pointwise approach is strongly affected by the signal-dependent nature of the speckle data when the spread of intensity fluctuations depends on the intensity itself. The latter leads to erroneous activity determination at non-uniform distribution of intensity in the laser beam for the non-normalized estimates. Normalization of the estimates, introduces errors. We propose to apply binarization to the acquired speckle images by comparing the intensity values in the temporal sequence for a given spatial point to the mean intensity value estimated for this point and to evaluate a polar correlation function. Efficiency of this new processing algorithm is checked both by simulation and experiment.

Azopolymers are one of the most efficient types of media for recording the polarization state of light. An essential optical parameter to characterize them is the value of the birefringence Δ n induced on illumination with polarized light. Laser beam is used as a pump and the birefringence is commonly probed by another laser with wavelength, different from the pump one. However, data about the spectral behavior of Δ n are given rarely. In this work we present experimental data for the dynamics of spectra of birefringence during illumination with pump lasers with wavelengths varying from 355 nm to 514 nm i.e. from the peak of absorbance to the edge of the absorbance band of the azopolymer used. Furthermore, we investigate the influence of nanoparticles from zinc oxide (ZnO) with different concentrations, incorporated in the azopolymer. The azopolymer used for this study is the water soluble poly[1- [4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt], shortly denoted as PAZO. As indicated by our experiments, thin films from this azopolymer can be used for polarization diffractive elements, operating in the entire visible range of the spectrum.

Azopolymers are well known organic materials for polarization holographic recording due to the induced anisotropy under illumination with polarized light. They possess all the desirable characteristics of the known polarization-sensitive materials, as high sensitivity and reversibility, but excel them substantially in the magnitude of the photoinduced birefringence. This makes possible to record reversible polarization gratings with high diffraction efficiency. In this paper results of experimental investigations on the reversibility properties of birefringence photoinduced in azopolymers are reported, depending on the conditions of subsequent optical and thermal treatment. Thin films of different polymers were prepared in order to examine the kinetics of multiple recording and erasure of birefringence in different types of azopolymers. The reversibility of the polarization recording has been studied using two different method of erasure – by increased temperature and on illumination with circularly polarized light.

Holography is defined as a two-steps process of capture and reconstruction of the light wavefront scattered from three-dimensional (3D) objects. Capture of the wavefront is possible due to encoding of both amplitude and phase in the hologram as a result of interference of the light beam coming from the object and mutually coherent reference beam. Three-dimensional imaging provided by holography motivates development of digital holographic imaging methods based on computer generation of holograms as a holographic display or a holographic printer. The holographic printing technique relies on combining digital 3D object representation and encoding of the holographic data with recording of analog white light viewable reflection holograms. The paper considers 3D contents generation for a holographic stereogram printer and a wavefront printer as a means of analogue recording of specific artifacts which are complicated objects with regards to conventional analog holography restrictions.

The paper reports on phase-only spatial light modulator implementation of an optical simulator of speckle patterns with controllable spatially varying evolution in time for algorithms testing in dynamic speckle metrology of physical or biological activity.

We study the optical characteristics of tantalum pentoxide films, deposited by reactive sputtering. These films, as many other metal oxide layers, are promising candidates for optical devices in the spectral region where they have no absorption. Besides applications in modern optics, they are also investigated as high-kappa materials for the needs of nano-electronics, i.e. design of dynamic random access memories, etc. Herein, we present results on optical functions of Ta2O5 films with physical thickness of ~15 nm. The spectral range of evaluation covers 210–750 nm. We have estimated the Ta2O5 optical functions from spectro-photometric data. The Tauc–Lorentz–Urbach parametric model was used in the fitting procedure, which was based on the stochastic genetic algorithm.

Intensity-based pointwise algorithms for 2D evaluation of activity in optical metrology with dynamic speckle analysis are studied. They are applied to a temporal sequence of correlated speckle patterns formed at laser illumination of the object surface. A new algorithm is proposed that provides the same quality of the 2D activity map but at less computational effort. acceptedVersion

In this paper, we evaluate the optical response of a stack of two diffraction gratings of equal one-dimensional periodicity. The first one is a surface-relief grating structure; the second, a volume polarization grating. This model is based on our experimental results from polarization holographic recordings in azopolymer films. We used films of commercially available azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]), shortly denoted as PAZO. During the recording process, a polarization grating in the volume of the material and a relief grating on the film surface are formed simultaneously. In order to evaluate numerically the optical response of this "hybrid" diffraction structure, we used the rigorous coupled-wave approach (RCWA). It yields stable numerical solutions of Maxwell's vector equations using the algebraic eigenvalue method.

Polarization holographic gratings (PHG) were recorded using a laser emitting a wavelength of 491 nm in thin films of the (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]) azopolymer, shortly denoted as PAZO. Thin azopolymer films with various thicknesses were spin-coated on plastic and glass substrates. Four different polarization states of the recording beams were used, and the results compared: a) two vertical linear polarizations, b) horizontal and vertical linear polarizations, c) linear polarizations at +45° and –45° relative to the recording plane, and d) two orthogonal circular polarizations – left- and right-handed (LCP and RCP). The diffraction efficiency in the +1 diffraction order was monitored in real time by a probing laser beam at the wavelength of 635 nm. The results indicate that the highest diffraction efficiency is achieved when recording with orthogonal polarizations – linear at ±45° or left and right circular. This is explained by the ability of the azopolymer material to record the variations in the polarization state of light better than the variations in its intensity. The holographic gratings obtained can be used to enhance the light-extraction efficiency of an OLED device.

In this article we present a study of the photoinduced birefringence (Δn) in films of a water soluble azopolymer: poly[1- [4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). Varying the concentration of the azopolymer in the solution, films with wide range of thicknesses are obtained – from 50 to 2500 nm. The film thickness is determined with a Talystep precision profilometer. Birefringence is measured using a polarimetric setup with a recording laser at 473 nm and probe He-Ne laser at 633 nm. As shown experimentally, the maximal photoinduced birefringence (Δn max ) does not depend on the thickness and is of the order of 0.07 for all of the investigated samples. The recording time however considerably increases for films thicker than 500 nm.

In this paper we present a study of the photoinduced anisotropy in novel nanocomposite films of azopolymers doped with ZnO nanoparticles with different sizes – 50 and 100 nm. The photoresponse was evaluated by classical polarimetric setup with two crossed polarizers, recording laser with wavelength 473 nm and probe He-Ne laser. Our experimental results indicate that doping with both 50 and 100 nm sized particles improves the response time, however the smaller size nanoparticles provide increase of u n max with up to 40%, as the 100 nm particles reduce the saturated value of the birefringence, due to the higher scattering. Keyword list: Nanocomposite materials, Photoinduced anisotropy, Polarimetric measurement, Optical Polarization 1. INTRODUCTION Since Todorov at al. 1 demonstrated in 1984 the possibility to record high-efficient polarization holographic gratings in azobenzene-containing materi als, they became subject of intensive re search. The observed high efficiency is due to the high values of the photoinduced anisotropy (mostly birefringence) based on the selective trans-cis isomerization and the consecutive reorientation of the trans azobenzenes

Dichromated gelatin (DCG) is one of the best light-sensitive materials for holographic recording. However, strict technological control should be observed during deposition, gelation, and drying of DCG plates and the chemical processing of the recorded structures. Usually, for reflection holograms the gelatin layer should be sealed in order to protect it from ambient humidity, which affects the value and position of the reflection maximum. Herein we give three different recipes for tuning the reflection maximum from 430 to 700 nm by swelling the hologram thickness with a filler material that is commercially available. The mechanism of the hologram swelling, which changes the period of the recorded holographic structure, is also briefly discussed.

Basic holographic characteristics of a newly developed panchromatic ultrafine grain silver halide light sensitive material for RGB recording of reflective holographic screen for autostereoscopic 3D display are presented. The average grain size is less than 10 nm which ensures high resolution, diffraction efficiency, and signal-to-noise ratio (more than 100 : 1) in a large dynamic range for RGB reflective holographic recording. The decrease of the diffraction efficiency in recording of scattering objects is less than 30% from the maximal values for specular reflection. The analysis of color recording of the reflective holographic screen with one viewing zone is presented on the basis of the so-called “sandwich†structure built of two layers for multiple holographic recording in blue, green, and red spectral regions.

Hybrid materials synthesized by combining polymers and inorganic nanoparticles (NPs) have received considerable attention recently due to their advantageous electrical, optical, or mechanical properties. Here we present a polarimetric study of thin films prepared from photoanisotropic hybrid materials: azopolymer (poly [1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with different concentrations of ZnO NPs with sizes below 50 nm. To obtain full information about the polarization response of these thin films, we determined the kinetics of the Stokes parameters of light passing through the films on illumination by linearly polarized light within the absorption band of the material, namely 473 nm. Using the Stokes parameters, the birefringence values were calculated as a function of time and compared for the films with different NP concentrations.

We present a study of the photoinduced birefringence in nanocomposite films of an azopolymer (PAZO) doped with goethite (a-FeOOH, a characteristic antiferromagnetic material) nanoparticles (NPs). The NPs had an elongated shape with a size 15×150 nm, i.e., a ratio of 1:10. Samples were prepared with different concentrations of the NPs in the azopolymer varying from 0% (undoped azopolymer film) to 15 wt %. An unusual dependence of the birefringence on the concentration was observed - two peaks of enhancement at 1 % and at 10 % concentration. Our previous studies on ZnO and SiO2 NP have indicated only one peak of increase at low concentrations - 0.5 wt % and 2 wt %, respectively. This effect could be related to the elongated shape of the nanoparticles and the presence of two characteristic NPs sizes - 15 and 150 nm. Moreover, the birefringence increase for the samples with 10 wt % NPs concentration (compared with the non-doped samples) was rather significant - nearly 70%.

Intensity-based pointwise non-normalized algorithms for 2D evaluation of activity in optical metrology with dynamic speckle analysis are studied and compared. They are applied to a temporal sequence of correlated speckle patterns formed at laser illumination of the object surface. Performance of each algorithm is assessed through the histogram of estimates it produces. A new algorithm is proposed that provides the same quality of the 2D activity map for less computational effort. The algorithms are applied both to synthetic and experimental data.

Hybrid materials based on combination of polymers and inorganic nanoparticles (NP) attracted considerable attention in the last decade due to their advantageous electrical, optical, or mechanical properties. Recently, we reported a significant improvement of the photoresponse by doping azopolymers with ZnO NP. To study the influence of the composition of the dopant, in our present work we have synthesized anisotropic organic/inorganic nanocomposite materials by incorporating 5-15 nm sized SiO2 NP in a side-chain azopolymer. As a result we observe an enhancement of the photoinduced birefringence in these composite materials with about 20% compared to the nondoped sample. Additionally, we discuss possible mechanisms leading to this enhancement related with the scattering caused by the NP and the increased mobility of the azochromophores in the vicinity of NP.

Holography enables capture and reconstruction of the optical field scattered from three-dimensional (3D) objects. The hologram encodes both amplitude and phase of the field under coherent illumination, whereas photography records only the amplitude by incoherent light. 3D visualization feature of holography motivates expansion of research efforts dedicated to digital holographic imaging methods as a holographic display or a holographic printer. The paper presents two holographic 3D printing techniques which combine digital 3D representation of an object with analog holographic recording. Generation of digital contents is considered for a holographic stereogram printer and a recently proposed wavefront printer. These imaging methods could be applied to specific artifacts which are difficult to be recorded by conventional analog holography.

Recently, an enhanced optical transmission (EOT) through 2D periodic arrays of sub-wavelength holes in a metal layer was found. It generated intense theoretical and experimental research, but its physical nature is still not elucidated. In this communication, we report experimental investigations on ID relief gratings, and numerical analysis of the composite structure of randomly distributed dielectric nanoparticles embedded in a thin metallic matrix. We show that EOT is also present in such structures.

Photoinduced chiral structures in four azopolymers (three amorphous and one LC) are quantified by the azimuth rotation angle Δθ. Both kinetics of Δθ and its dependence on the input ellipticity are presented.

We describe the optimization of the holographic patterning of sub-micrometre surface relief structures in an acrylamide-based photopolymer. A substantial improvement in the photoinduced surface relief resolution was achieved by altering the photopolymer chemical composition and by introducing a single step post-recording thermal treatment of the layers. It was observed that, by optimization of the chemical composition of the photopolymer layers, the maximum achievable spatial frequency increases from 200 to 550 lines/mm. The improvement of the surface relief amplitude by alteration of the chemical composition is limited due to the fact that both decrease of the plasticizer and increase of the monomer concentrations result in less stable photopolymer layers. In order to obtain further improvement in the spatial frequency resolution a thermal treatment of the layers was implemented. It was observed that baking of the layers at temperatures ranging from 120 to 220 °C at a rate of 1 °C min − 1 makes possible the inscription of surface relief profiles with a sub-micrometre period of 650 nm and amplitude of 15 nm.

Digital image processing is an important area of preservation and representation of cultural and historical objects. Part of it is the task of cleaning images corrupted by noise. Many different methods and approaches have been successfully implemented, but still filtering and denoising techniques are developing and improving intensively. Herein, we report numeric simulations of 2D image filtering. Effects of impulse noise are very efficiently reduced by adaptive median filtering. The situation of additive noise, which itself depends on the intensity of the original image, is more complicated. However, we demonstrate that in this case the use of wavelet transforms in the denoising procedure is very productive and promising.

The paper is dedicated to analysis of normalized intensity-based pointwise algorithms for processing dynamic speckle images with spatially varying speckle statistics in non-destructive visualization of regions of faster or slower changes across an object. Both existing and newly proposed algorithms are analyzed. Extraction of speed of changes is done by acquiring correlated in time speckle images formed on the object surface under laser illumination. The studied algorithms have been applied to simulated low and high contrast speckle data. Their performance has been compared to processing of binary patterns as another approach for dealing with varying speckle statistics in the acquired images. The efficiency of the algorithms have been checked on the experimental data, including data in a compressed format. We have proven that the algorithms with normalization at successive instants by a sum of two intensities or a single intensity outperform as a whole the algorithms which apply the time-averaged estimates of the mean value and the variance of speckle intensity.

International audience; In this chapter, a compilation of different systems able to photogenerate active radicals toward polymerization reaction( type I, type II and three component photoinitiating systems) for application in holographic grating recording when associated to monomers is reviewed. In particular, the visible curable system is associated to fluorinated acrylate monomers formulation for creation of transmission gratings. The PIS efficiencies are presented in term of diffraction grating yields and compared to photopolymerization experiments. The special case of photocyclic initiating systems is described in details, its influence on the grating built up being discussed on the basis of selected mixtures using visible dyes, electron donors (e.g. amines), electron acceptors (e.g. iodonium salts) or hydrogen donors as coinitiators. The role of the photochemical properties of dye on the performance of the holographic recording material is investigated through time resolved and steady state spectroscopic studies of the PIS (e.g. nanosecond laser flash photolysis), to highlight the photochemistry underlying active radicals photogeneration. In order to get more insight into the hologram formation, grating formation curves were compared to those of monomer to polymer conversion obtained by real time Fourier transform infrared spectroscopy (RTFTIR). This work outlines the importance of the coupling between the photoinitiating system (i.e. the photochemical reactions) and the holographic resin.