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The article discusses the use of computer-generated holograms (CGHs) for the application as one of the security features in the relief-phase protective holograms. An improved method of calculating CGHs is presented, based on ray-tracing approach in the case of interference of parallel rays. Software is developed for the calculation of multilevel phase CGHs and their integration in the application of security holograms. Topology of calculated computer-generated phase holograms was recorded on the photoresist by the optical greyscale lithography. Parameters of the recorded microstructures were investigated with the help of the atomic-force microscopy (AFM) and scanning electron microscopy (SEM) methods. The results of the research have shown highly protective properties of the security elements based on CGH microstructures. In our opinion, a wide use of CGHs is very promising in the structure of complex security holograms for increasing the level of protection against counterfeit.

In this paper we present the synthesis and optical properties of amorphous low molecular compound 4-((4-(bis(5,5,5-Triphenylpentyl)amino)phenyl)diazenyl)benzoic acid. The surface relief gratings formation by polarization holography method on these thin films (thicknesses are 200–1700 nm) was shown. The dependence of the surface relief modulation on various parameters: recording exposure dose, the polarization state of the recording beams, the grating period and the film thickness of the material was demonstrated. Values of surface tension at the air-film before and after irradiation of the substance by polarized radiation were measured. The efficiency of surface relief formation in different medium was compared. The possibility of practical application of 4-((4-(bis(5,5,5-Triphenylpentyl)amino)phenyl)diazenyl)benzoic acid in the holography as a non-etching photoresist was showed.

New combined embossed hologram originating technique was developed by the international team of holography experts. The technique merges deep 3D holographic images with commonly used hologram security features. Deep 3D images were first recorded on photoresist with Geola's holographic printer containing their proprietary pulsed laser. Optical security features were then overexposed onto the photoresist plates containing latent images of deep 3D scenes. The photoresist plates with several exposures (containing optical security features and deep 3D images) were developed. Embossed holograms, containing such effective public security features as full colour 3D images, guilloches, rainbow patterns were manufactured. Manufactured embossed holograms also contained such optical security features as microtext and laser readable hidden image.

Two different grating formation geometries for recording onto the positive-tone photoresist with pulsed laser and continuous-wave sources are analyzed and compared. Diffraction efficiency measurements and atomic force microscopy (AFM) examination have been performed in order to investigate the optical and topographical properties of the recorded structures. Gratings patterned by a continuous-wave laser and by a pulsed laser working in the single pulse and multipulse regimes showed different surface roughness and optical properties. The possible reasons for surface roughness and effective exposure differences between gratings created with pulsed and continuous-wave laser radiations are discussed. The processing schemes for diffractive structures patterned by pulsed laser onto positive-tone photoresist for commercial hologram production are analyzed and presented in this work.

Physics Holographic Recording Device Based on LCoS Spatial Light ModulatorA PC-controlled holographic recording device has been developed in which a LC-R-2500 Spatial Light Modulator (SLM) based on reflective Liquid Crystal on Silicone (LCoS) display was used. The device allows the amplitude and phase modu-lation of coherent light wave fronts. In the optical scheme, a DPSS (Diode Pumped Solid State) laser with nanosecond pulse duration and wavelength 532 nm was applied. The holographic recording was made and tested in the amplitude and phase wave front modulation modes on a chalcogenide semiconductor photoresist As40S15S45. The experimental results are presented.

Principles of Creation and Reconstruction of Dot-Matrix HologramsA method for calculation of dot-matrix holograms is presented, whose distinction from other methods is simplicity of the formulas for the parameters of each pixel element in a hologram. At the Innovation Spectroscopy Center of DU a device for recording dot-matrix holograms has been designed, with a program using the pro-posed method for their calculation. Holograms 50x50 mm in size well corresponding to the initial graphic design were obtained.

Electric field-induced second harmonic (EFISH) generation effect in paraelectric lanthanum doped lead zirconate-titanate ceramics (PLZT) has been utilized in the local oscillator device of nonlinear optical heterodyne interferometer. Application of PLZT X/65/35 plates in low frequency rotating electric field as the reference sources of EFISH for interferometric analysis of anisotropy of thin films or surfaces of crystals is proposed. Experimental details and properties of multiphase PLZT EFISH modulator has been discussed.

The present article is focused on the optical properties of amorphous As-S-Se thin films and chemical wet-etching in organic non-aqua amine-based solution. Different etching rates depending upon the sample exposure dose and etchant concentration were found. The maximum selective etching ratio 7:1 for samples was achieved. An interference method of in situ real-time monitoring of etching rate for the area with different exposure doses for the same sample was proposed. The efficiency of formation of relief gratings for amorphous As-S-Se thin films depending on the exposure dose was studied. Quality holographic gratings with diffraction efficiency (DE) of up to 65% were received. The results of the current study demonstrate an adequate etching selectivity for fabricating micro structures and possibility of practical application of amorphous chalcogenide thin films in holography and optical lithography.

The given work investigates principles of recording, calculation, and security aspects of ‘hidden image’ effect in digital holograms that are intended for security applications. Dot-matrix and image-matrix technologies of optical recording can be widely used for recording protective holograms with such type of security features. When a collimated laser beam falls on and then is reflected from the section of holograms, containing a protective ‘hidden image’ element, a graphic image can be seen in the projection of diffracted light on the frosted screen. The present work also discusses a method of personalizing the ‘hidden image’ effect with the help of laser demetallization. In this way the hidden image can be individualized for each hologram sticker and contain additional information such as a number, text or logotype. The attractiveness of this method is in the possibility of achieving a considerable increase of the protective characteristic of holograms and incorporating additional variable information in them, as well as in providing both visual and automatic ways of checking authenticity of a hologram.

We report optical and luminescence properties of 3-N, N-diacetylaminobenzanthrone thin films deposited on glass substrate by thermal evaporation. The structural and optical properties of organic thin films were studied by means of the confocal microscope with an input of femtosecond laser radiation, X-ray diffractometer, and scanning electron microscope (SEM). Intense luminescence with the maximum at 530 nm was observed when excited by laser radiation with the wavelengths 458, 476, 488, 496, 514 nm. In addition, the luminescence caused by two-photon absorption of femtosecond (fs) laser radiation has been investigated. Semi empirical calculations by AM1 and ZINDO/S methods and ab initio calculations using Gaussian software were carried out to estimate the electron system of structure. The calculations show planar configurations for the aromatic core and diacetylamino fragment of this compound. The study of the structure of benzanthrone derivative thin films with X-ray diffraction (XRD) methods, indicates the distance between molecular layers and ordered molecular fragments.

After the invention of holography and development of hologram micro-embossing, mass replication of hologram became possible. Use of a hologram as a security option for valuable documents and products was soon realized and won a large-scale application, which did not hinder development of other security features though. A great variety of other diffractive microstructures commonly known as diffractive optically variable image devices (DOVID) has appeared. Alongside the development of computer technology, digital holographic recording in applied holography has acquired a wide range of application. Nowadays, various types of digital holograms are used for protection and identification of industrial products and documents against counterfeiting, as well as for packing and decorating. Now two optical technologies for digital recording of protection holograms and DOVID, having similar principle of image formation, are widely used: dot-matrix and image-matrix holographic recordings (Pizzanelly, 2004). A dot-matrix hologram consists of an array of fine diffractive dots holding an image together (Fig. 1a). Each dot in such a hologram consists of a uniform diffraction pattern in which the grating pitch and grating orientation

The electron beam (EB) induced changes in solubility of thin As-S-Se films have been studied. Optimal absorption current choice, nano structure relief and shape dependence on acceleration voltage discussed. The possibilities of practical use of these materials as resist for gratings and optical diffractive element production using EB. New results are presented that indicate chalcogenide glasses as promising electron beam resists.

Electron beam (EB) induced changes in thin films of the amorphous chalcogenide semiconductors As-S-Se have been studied. The experimental results on patterning of As-S-Se film surfaces by EB exposure and following chemical etching are presented. The possibilities of practical application of this material as resists for the production of relief holograms and diffractive optical elements (DOE) are discussed.

The given work investigates a way of integrating Diffractive Optical Elements (DOE) in the structure of a protective image-matrix hologram. An important feature of the suggested method is simplicity of realization by some modification of the frames exposure software and full hardware compatibility with image-matrix technology. Unlike other methods, the suggested one does not require changing the optical scheme between transitions from recording holographic frames area to the DOE ones and vice versa. Any shape of DOE in the hologram approximated to the size of the frame is available. A DOE frame cannot contain any part of a holographic region due to the different method of exposure. The minimal size of one DOE pixel is about 3 micrometer. The method under discussion allows for recording both binary (two-phase) and multilevel (multi-phase) DOE at corresponding calibrations of the employed Spatial Light Modulator (SLM). The method has passed an experimental approbation and is now used for embedding DOE into an image-matrix hologram as an additional security element.

As-S-Se chalcogenide thin films are successfully employed in classical and dot-matrix holography as inorganic photoresists for obtaining a relief-phase hologram. However using these films for image-matrix hologram recording has not been studied due to some features of image-matrix technology. For the applied research of the optical properties of As-S-Se films an experimental device of digital image-matrix holographic recording based on 100 mW 405 nm semi-conductor laser and Spatial Light Modulator (SLM) has been created. The device has the following main parameters: 140 × 105 µm frame size; laser intensity during exposure 10 W/cm2. With the help of this device diffraction grating and security holograms were recorded on As-S-Se thin films. The work reported herein presents results of an experimental study of how diffraction efficiency (DE) of the received relief-phase holographic gratings depends on an exposure and period. Diffraction grating profiles and speed of etching corresponding to different exposure doses are shown. Hologram samples with DE = 65% have been received which allows for using chalcogenide film as alternative to organic photoresists in applied dot-matrix and image-matrix holography.

We have performed the investigation of dot matrix holographic recording in amorphous As2S3 chalcogenide films with different thickness on Al coated glass substrates. The control over the interference minimum of reflection during the evaporation process allowed obtaining As2S3-Al system with a minimum value of initial reflection in defined spectral region. The investigation of dependence of diffraction efficiency of holographic recording on both film thickness and initial conditions of reflectivity in the system was performed. The main advantage of this type of system is the possibility to increase optical sensitivity of material in predefined spectrum region for phase hologram recording.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The films based on the low-molecular amorphous azochromophore 2-(3-(4-((4- (Ethyl(2-(trityloxy)ethyl)amino)phenyl)diazenyl)styryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (IWK-2M) were prepared. The optical properties of the material, such as transmittance and reflection spectra of the film, sensitivity to polarization holographic recording by two wavelengths (405 and 532 nm) were studied. The direct relief formation during the polarization holographic recording was explored, relief depth dependence on exposure and record beam intensity was investigated. The holographic matrix on this material base was produced without chemical etching process; the replication of holographic image was performed.

We have developed PC controlled dot-matrix holographic recording system based on the CW diode pumped YAG:Nd SHG laser (wavelength 532 nm, power 30mW,) modulated electronically with TTL signals. Two-beam technique has been used with convergence angle 30o and PC controlled incident beam plane rotation 0-360o. Optical system consists of beam splitter, 40mm focus length forming cylindrical lens and 40mm focusing lens. Characteristic parameters of experimental equipment are following: spot size - 50-200 micrometers, direct laser writing area, limited by x-y positioning system, was 70mm x 70mm, number of writing head rotation positions up to 256 (8 bit), time of each exposure - 1-1000 msec. As the recording material we have used AsxSySe1-x chalcogenide glass material. Diffraction efficiency of written gratings in the material in dot-matrix regime exceeds 25%. Original method for surface relief enhancement by etching and subsequent electroplating has been developed. Special PC controlled device for thermal imprinting of relief holograms on the metallized polyamide film has been built. Measurements of light transmission, reflection, and diffraction phenomena of laser beams in processed chalcogenide materials are discussed.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The composite films based on PMMA and CuCl2 were prepared. Transmission spectra of the films before and after illumination by different laser lines (405, 448, 456 nm) were measured. The reversible character of the composite photosensitivity was fixed. The phenomenon of direct surface relief formation after laser beam illumination of composite films was described. The holographic gratings were recorded by different exposure (200 – 500 J/cm2) in the films with different concentration (8 and 20 wt. %) of copper salt. The film sensitivity dependence on polymer molecular weight was studied. Surface relief of the gratings was measured by AFM.