Holographic interferometry for security and forensic applications.

Security holograms having unique 3D images are one of the tools for enhancing the security for product and personnel authentication and anti-counterfeiting. Apart from the high technology that is required, the uniqueness of a 3D object presents a significant additional threshold for the counterfeiting of such security holograms. But, due to the development of 3D printing technology, the hurdles are disabled and allow the chances of counterfeiting. In order to overcome this, holographic interferometry is effectively utilized and the object is recorded twice before and after the state of random object change. At the time of reconstruction, two signal waves generated simultaneously interfere each other, resulting in a fringe modulation. This fringe modulation in 3D image hologram with respect to the random object change is exploited to generate a rigid and unique anticounterfeit feature. Though holographic interferometry techniques are being widely used for the non-destructive evaluation, the applicability of this technology for the security and forensic activity is less exploited. This paper describes our efforts to introduce holographic interferometry in 3D image holograms for security and forensic applications

Effect of oxygen pressure on the structural and optical properties of BaSnO3 films prepared by pulsed laser deposition method.

BaSnO3 thin films were deposited on quartz substrate by pulsed laser deposition technique under different background oxygen pressures and the effects of oxygen pressure on the structural, morphological and optical properties of BaSnO3 thin films are systematically investigated using different characterization techniques. The BaSnO3 films deposited without and with oxygen pressures are polycrystalline in nature with cubic crystalline phase. Moderate oxygen ambience favors enhanced crystallinity of the BaSnO3 films and 0.02 mbar is found to be optimum oxygen pressure for highest crystallinity. The surface morphology of the deposited films was strongly affected by the oxygen pressure in the deposition chamber. A systematic increase of film thickness and decrease of RMS surface roughness is observed with increase in oxygen pressure. XPS analysis reveals that barium is in the + 2 oxidation state and Sn is in the + 4 oxidation state in the film deposited at optimum oxygen pressure of 0.02 mbar. The deposited BaSnO3 films have photoluminescence emissions in the visible region and have high transmittance in the visible and infrared regions. The BaSnO3 films deposited at oxygen ambience shows a blue shift in the optical band gap. The optimized film shows high crystallinity, high value of transmittance and wide band gap energy which indicates its suitability for optoelectronic devices

Microstructure encryption and decryption techniques in optical variable and invariable devices in printed documents for security and forensic applications.

Today, document counterfeiting is a global menace because of the advanced technologies available at ever decreasing prices. Instead of eschew the paper documents; applying efficient cost effective security methodologies are the feasible solutions. This paper reports a novel cost effective and simple optical technique using micro text encrypted optical variable device (OVD) threads, ultra-violet (UV) based optical invariable device (OID) patterns and artistic fonts for secure preparation of the documents and its forensic application. Applying any one of the above technique or together can effectively enhance the level of security of the most valuable document. The genuineness of the documents can be verified using simple decryption techniques

Effect of RF power on the structural and optical properties of zinc sulfide films.

Zinc sulfide (ZnS) films were prepared via a radio frequency (RF) magnetron sputtering technique using different RF powers (100, 120, 150, and 180 W), and the effects of the RF power on the structural and optical properties of the films were studied using x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, ultraviolet-visible spectroscopy, spectroscopic ellipsometry, and laser photoluminescence spectroscopy. It was found that the RF power has an important impact on the predominant phase formation and crystallinity of the ZnS films. The film thickness, refractive index, and film to bulk relative density increase systematically with an increase in the RF power. Among the various RF power values investigated, 150 W was optimal for the growth of highly crystalline ZnS films with a predominance of the cubic phase and enhanced photoluminescence emissions

Effect of electron beam irradiation on structural and optical properties of Cu-doped In2O3 films prepared by RF magnetron sputtering.

Undoped and Cu-doped In2O3 films were prepared by radiofrequency magnetron sputtering technique. The effects of Cu doping and high-energy electron beam irradiation on the structural and optical properties of as-prepared films were investigated using techniques such as x-ray diffraction, x-ray photoelectron spectroscopy (XPS), lateral scanning electron microscopic image analysis, energy-dispersive x-ray (EDX) spectroscopy, micro-Raman, and ultraviolet-visible (UV-vis) spectroscopy. Moderate doping of Cu in In2O3 enhanced the intensity of (222) peak, indicating alignment of crystalline grains along . Electron beam irradiation promoted orientation of crystalline grains along in undoped and moderately Cu-doped films. EDX spectroscopic and XPS analyses revealed incorporation of Cu2+ ions in the lattice. The transmittance of Cu-doped films decreased with e-beam irradiation. Systematic reduction of the bandgap energy with an increase in Cu doping concentration was seen in unirradiated and electron-beam-irradiated films

Highly transparent and luminescent nanostructured Eu203 doped ZnO films.

Zinc oxide is a wide, direct band gap II-VI oxide semiconductor. Pure and Eu-doped ZnO films are prepared by RF Magnetron sputtering at different doping concentrations (0.5, 1, 3 and 5 wt %). The films are annealed at 500 0C in air for two hours. The structural, morphological and optical properties of the films are characterized using XRD, micro-Raman, AFM, UV-Visible and photoluminescence spectroscopy. The thickness of the films is measured using stylus profilometer. XRD analysis shows that all the films are highly c-axis oriented exhibiting a single peak corresponding to (002) lattice reflection plane of hexagonal wurtzite crystal phase of ZnO. The micro-Raman spectra analysis reveals the presence of E2 high mode in all the samples which is the intrinsic characteristic of hexagonal wurtzite structure of ZnO. The appearance of LO modes indicates the formation of defects such as oxygen vacancies in the films. AFM micrographs show uniform distribution of densely packed grains of size with well defined grain boundaries. All the films exhibit very high transmittance (above 80%) in the visible region with a sharp fundamental absorption edge around 380 nm corresponding to the intrinsic band edge of ZnO. All the films show PL emission in the UV and visible region. Paper presented at the 2nd International Conference on Structural Nano Composites (NANOSTRUC 2014) held 20-21 May 2014 in Madrid, Spain

Effect of tungsten doping on the properties of In2O3 films.

Highly crystalline tungsten oxide (WO3)-doped indium oxide (In2O3) films are synthesized at room temperature by the RF magnetron sputtering technique. The structural and morphological properties of the as-deposited films and the films annealed at a temperature of 300°C are investigated in detail. X-ray diffraction analysis reveals the presence of a cubic bixbyite structure with preferred orientation along the (222) plane for both the as-deposited and annealed films. Moderate WO3 doping (1 wt.%) enhances the crystallinity of the as-deposited In2O3 films, whereas the crystallinity of the films systematically decreases with an increase in WO3 doping concentration beyond 1 wt.%. Raman spectral analysis discloses the modes of the cubic bixbyite In2O3 phase in the films. Atomic force microscopy micrographs show a smooth and dense distribution of smaller grains in the films. X-ray photoelectron spectroscopy reveals the existence of W5+ in the doped films. The undoped film is highly oxygen deficient. Variation in the concentration of oxygen vacancy can be associated with the degree of crystallinity of the films

Design of a smart security registration plate for seagoing motorized non-mechanical crafts.

Unauthorized and uncertified small seagoing fishing crafts are being widely used for illegal, unreported and unregulated fishing, especially in the Indian sub-continent. Nevertheless, the registration is mandatory; the display of the registration mark and its standards for the seagoing fishing craft has not been specified in detail. Now, any fraudster can mark a fake registration number quite easily on the craft and can be used for criminal activities in the coastal areas because of the effortless wipe out possibility for the present registration marks. Thus due to the lack of standardization and regulation for the display of registration number plate for the seagoing craft, identification of genuine one is very difficult. This paper proposes a typical design of a Smart Security Registration Plate (SSRP) using Radio Frequency Identification (RFID) technology to provide secure authentication of the motorized non-mechanical fishing crafts

Highly ordered good crystalline ZnO-doped WO3 thin films suitable for optoelectronic applications.

Highly ordered ZnO-doped WO3 thin films with good crystalline quality are prepared using radio frequency magnetron sputtering technique, and its morphological and structural properties are studied using various characterization tools such as field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction technique, micro-Raman spectroscopy, and x-ray photoelectron spectroscopy. Morphological analysis shows a smooth surface for pure film, whereas the ZnO-doped films presents a dense distribution of grains of larger sizes with well-defined grain boundary. X-ray diffraction studies reveal the enhancement of crystalline quality of the films with increase in ZnO doping concentration up to 5 wt.%, beyond which the crystalline quality gets deteriorated. A phase modification from a single monoclinic WO3 phase to mixed monoclinic WO3 and W18O49 phases is observed for films with higher ZnO doping concentrations

Influence of Pr doping on the structural, morphological, optical, luminescent and non-linear optical properties of RF-sputtered ZnO films.

The effects of Pr doping on the structural, morphological, optical and non-linear optical properties have been investigated. X-ray diffraction and Raman analysis reveals the formation of highly c-axis-oriented films with hexagonal wurtzite structure of ZnO. Atomic force microscopy and scanning electron microscopy images reveal the formation of grains with well-defined grain boundaries. The Pr-doped films present excellent optical transparency in the visible region. The photoluminescence spectra show both UV and visible emissions and the intensity of the visible emission increases with Pr doping. Nonlinear optical properties of the Pr-incorporated ZnO nanostructures have been investigated using the open aperture Z-scan technique. It is interesting to note that 1wt.% praseodymium-incorporated ZnO film shows saturable absorption, whereas the 5wt.% praseodymium-incorporated ZnO shows reverse saturable absorption and the high value of non-linear absorption coefficient (β) for 5wt.% Pr-doped ZnO film suggests the suitability of these films for optoelectronic device applications