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The rare Cu-Zn sulphate, ktenasite, was found in the association with schulenbergite, serpierite, gypsum and brochantite at abandoned stope of the Modrá štola adit, the ore deposit Zlaté Hory - East, Czech Republic. Ktenasite occurs there as two different (color, morphology) types, the first is olive green to dark green columnar crystals up to 4 mm in length which forms radially arranged groups or rich crystalline coatings. The second type is represented by blue to greenish blue crystalline coatings or hemispherical or fan-shaped aggregates formed by thin tabular crystals. The X-ray powder diffraction data, Raman spectra and chemical composition of both types are almost identical. Ktenasite is monoclinic, space group P21/c, the unit-cell parameters refined from X-ray powder diffraction data are: a 5.610(2), b 6.123(2), c 23.827(9) Å, β 95.27(3)o and V 815.0(4) ų. Its chemical analyses correspond to the empirical formula Zn1.00(Cu3.13Zn0.96Mg0.07Al0.01)Σ4.17(SO4)1.98(PO4)0.01(SiO4)0.01(OH)6.32·6H2O. Schulenbergite most often occurs only as an admixture in blue-green crystalline aggregates of ktenasite, sometimes together with serpierite. More rarely, its blue tabular crystals with a pearly luster up to 0.4 mm in size were also observed. Schulenbergite is trigonal, space group R-3, the unit-cell parameters refined from X-ray powder diffraction data are: a 8.187(3), c 7.012(4) Å and V 410.5(3) ų. Its chemical analyses correspond to the empirical formula (Cu4.96Zn2.34)7.30(SO4)1.92(SiO4)0.05(PO4)0.02 (OH)10.47·6H2O. Serpierite is relatively abundant in the studied mineral association, usually forms light blue fine crystalline coatings, its fan-shaped aggregates up to 4 mm in size formed by elongated tabular crystals have also been found more rarely. Its chemical analyses correspond to the empirical formula (Ca1.14Mn0.03Mg0.02)Σ1.19(Cu3.08Zn0.73)Σ3.81(SO4)1.99 (PO4)0.02(OH)5.97·3H2O. Abundant brochantite forms bright green crystalline coatings and tiny dark green to black-green crystals. Its chemical analyses correspond to the empirical formula (Cu3.80Zn0.17Al0.02)Σ3.99(SO4)0.99(PO4)0.01(OH)6.00. The origin of studied mineral association is connected with sub-recent weathering of primary sulphides (pyrite, pyrrhotite, sphalerite and chalcopyrite) in the conditions of abandoned mine space. [ABSTRACT FROM AUTHOR]

We propose a V-shaped phase grating to simultaneously improve the diffraction efficiency of the 1st order diffraction mode and suppression of high order modes. An analytic description is given that indicates the 0th, 2nd, 3rd, and 4th order diffractions can be completely suppressed while the 1st order absolute diffraction efficiency can reach a theoretical maximum of 27.72%, which is much higher than that reported from single order gratings, such as sinusoidal amplitude transmission gratings. The dependencies of the 1st order diffraction efficiency on the wavelength and depth deviations are also discussed. The experimental results show that the absolute efficiency of the 1st order diffraction is 25.85% while the 2nd, 3rd, and 4th order diffractions disappear completely, confirming the theoretical predictions. The diffraction patterns of a xenon lamp demonstrate the suppression of the high order diffractions from our quartz phase grating. The unique dispersive properties of the V-shaped phase grating make it attractive for broad spectroscopy and high-accuracy monochromatization applications. [ABSTRACT FROM AUTHOR]

A broadly tunable grating-coupled external cavity laser system in the green region is demonstrated by employing a commercially available broad-area green laser diode. A simple Littrow-type external cavity configuration was adopted, and two gratings with different diffraction efficiencies were used as the light feedback elements. When a grating with the first-order diffraction efficiency of 50% and the zeroth-order diffraction efficiency of 31% was used, a tuning bandwidth of 11.0 nm with an output power near 400 mW was achieved. When a grating with the first-order diffraction efficiency of 10% and the zeroth-order diffraction efficiency of 78% was used, a tuning bandwidth of 5.0 nm with an output power near 750 mW was achieved. Meanwhile, the spectral linewidth was narrowed significantly down to 0.08-0.18 nm from the free-running linewidth of 2.81 nm due to the external mode selection effect. Such high-power broadly tunable green EC lasers are important for second harmonic generation. [ABSTRACT FROM AUTHOR]

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 ≤ λ ≤ 5 μm) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem. [ABSTRACT FROM AUTHOR]

A periodic electric field is generated in the grating-like electrodes cell by an applied voltage and results in the reorientation of liquid crystals. The linearly polarized probe beam experienced periodic distribution of refractive index and formed a phase grating. He-Ne laser was used as the probe beam to detect the zeroth-order (o) and first-order (+1) diffraction intensities. The experimental results showed that the diffraction grating can be switched on by applying a small voltage. The optimal first-order diffraction efficiency is about 12%. The dependence of the first-order diffraction efficiency on the polarization of the probed beam is also discussed herein. [ABSTRACT FROM AUTHOR]

The chirped pulse amplification (CPA) technology is the main approach to achieve high-intensity short-pulse laser. Diffraction gratings are good candidates for stretching and compressing laser pulses in CPA. In this paper, a kind of gold-coated grating has been prepared and its laser damage experiment has been performed. The results reflect that the gratings laser damage was dominated by thermal ablation due to gold films or inclusions absorption and involved the deformation or eruption of the gold film. Based on these damage phenomena, a method of using a cover layer to prevent gold films from deforming and erupting has been adopted to improve the gold-coated gratings laser damage threshold. Since the addition of a cover layer changes the gratings diffraction efficiency, the gratings structure has been re-optimized. Furthermore, according to the calculated thermal stress distributions in gratings with optimized structures, the cover layer was demonstrated to be helpful for improving the gratings laser damage resistance if it is thick enough. [ABSTRACT FROM AUTHOR]

In this study we fabricate gold nanocomposites and model their optical properties. The nanocomposites are either homogeneous films or gratings containing gold nanoparticles embedded in a polymer matrix. The samples are fabricated using a recently developed technique making use of laser interferometry. The gratings present original plasmon-enhanced diffraction properties. In this work, we develop a new approach to model the optical properties of our composites. We combine the extended Maxwell--Garnett model of effective media with the Rigorous Coupled Wave Analysis (RCWA) method and compute both the absorption spectra and the diffraction efficiency spectra of the gratings. We show that such a semi-analytical approach allows us to reproduce the original plasmonic features of the composites and can provide us with details about their inner structure. Such an approach, considering reasonably high particle concentrations, could be a simple and efficient tool to study complex micro-structured system based on plasmonic components, such as metamaterials. [ABSTRACT FROM AUTHOR]

In this paper, photosensitive materials for information storage devices are presented. The polymers were prepared using surface relief-grating (SRG) fabrication with a diode-pumped solid-state (DPSS) laser of 532 nm and the diffraction efficiency (DE) of the polymers were assessed with a low-power DPSS laser at 633 nm. However, the diffraction efficiency of the azo-functionalized epoxy-based polymer was low, even after 15 min of exposure. To improve the efficiency and reduce the time it takes for the DE measurements of the photosensitive polymer, the polymer was combined ionic liquids (ILs). Various ILs, i.e., 1-methylimidazolium chloride ([Mim]Cl) from the imidazolium family of ILs and diethylammonium dihydrogen phosphate (DEAP), triethylammonium 4-aminotoluene-3-sulfonic acid (TASA) and tributylmethylammonium methyl sulphate (TBMS) from the ammonium family of ILs, were investigated. For the first time, it was observed that DE dramatically increased the DEAP-polymer mixture in 4 min compared to the polymer (alone) and other polymer-IL mixtures. Therefore, DEAP IL could help improve the efficiency of DE measurements in a shorter time. [ABSTRACT FROM AUTHOR]

The polarization holographic gratings recorded in Au nanoparticles-doped methyl orange/polyvinyl-pyrrolidone (MO/PVP) composite films were investigated. The polarization state of diffraction beams was controlled by a probe light and holographic gratings together. The first-order diffraction efficiency of the MO/PVP film doped with Au nanoparticles was measured to be 3.2 times larger than that of pure composite film. Meanwhile, an obvious enhancement of photoinduced birefringence of MO molecules was also demonstrated. This enhancement of diffraction efficiency and photoinduced birefringence was discussed in terms of the localized field effect via the surface plasmon resonance of Au nanoparticles, which was confirmed by finite-difference time-domain simulation. [ABSTRACT FROM AUTHOR]

Focusing of an optical vortex with sectorial azimuthal polarization is numerically investigated. An effect of sector numbers on the results of focusing is estimated. It is shown that the focal spot produced by a beam with six sectors does not differ from the ideally azimuthally polarized optical vortex; a difference in the focal spot diameter does not exceed 0.001 of the wavelength. For a four-sectoral beam, the difference does not exceed 0.028 of the wavelength. We have investigated a four-Sector transmission Polarization Converter for a wavelength of 633 nm, that enables the conversion of a linearly polarized incident beam into a mixture of linearly and azimuthally polarized beams. It was experimentally shown that light propagated through the four-Sector transmission Polarization Converter and focused by Fresnel zone plate with a focal length of 532 nm produces focal spot with diameters 0.46 and 0.57 of wavelength. [ABSTRACT FROM AUTHOR]

Linear displacement encoders are necessary in field of machine tools, metrology and electronic industry. Those devices provide nanometric resolution when constructed according to the interferometric scheme. Mathematical modeling of signal transfer process into its optical system to analyze an interference field is described. Signal intensity depending on a small displacement of moving grating phase shift correlations is considered. A sample model of the linear optical encoder is developed based on the optical scheme under research. [ABSTRACT FROM AUTHOR]

Diffraction gratings are among the most commonly used optical elements in applications ranging from spectroscopy and metrology to lasers. Numerous methods have been adopted for the fabrication of gratings, including microelectromechanical system (MEMS) fabrication which is by now mature and presents opportunities for tunable gratings through inclusion of an actuation mechanism. We have designed, modeled, fabricated and tested a silicon based pitch tunable diffraction grating (PTG) with relatively large resolving power that could be deployed in a spaceborne imaging spectrometer, for example in a picosatellite. We have carried out a detailed analytical modeling of PTG, based on a mass spring system. The device has an effective fill factor of 52% and resolving power of 84. Tuning provided by electrostatic actuation results in a displacement of 2.7μm at 40V. Further, we have carried out vibration testing of the fabricated structure to evaluate its feasibility for spaceborne instruments. [ABSTRACT FROM AUTHOR]

This is a proposal for a Fresnel lens with an electrically tunable binary-phase made of polymer dispersed liquid crystal (PDLC), which has relatively fast response time and low applied voltage. Simple fabrication is the major advantage of the proposed method. In this study, NOA65 and E7 were utilized with weight ratios of 60 wt.%: 40 wt.%. There was also the utilization of a relatively low intensity UV-light, 0.53 mW/cm2. The duration time of exposure was about 30 hours. The performance improvement of the Fresnel lens resulted from the infiltration of large LC droplet into the PDLC film. The phenomenon of black cross strip patterns could be explained with the use of the electro-hydrodynamics theory. The diffraction efficiency of the proposed lens was from 31.1 % to 41 % with the changes of externally applied voltage. This work presents an effective approach to get relatively complete phase separation in PDLC. The proposed method also provides great potential in developing high performance Fresnel lens. [ABSTRACT FROM AUTHOR]

The production of three dimensional blazed grating structures based on ultra-precision machining is an up-to-date issue. Hence, in the development of manufacturing technologies technology-related failure modes are generated due to structural variations. These failure errors must be recorded in cause and effect and then characterized by their type in order to achieve the optimum quality. This paper addresses the influence of processing parameters on the shape-persistence and hence on the grating quality and explains the possibility of detection and classification of them. [ABSTRACT FROM AUTHOR]

The enhancement factor for surface plasmon-polaritons scattering by a thin dielectric grating was measured experimentally. Scattering of a p-polarized wave may be up to 30,000 times stronger than the non-resonant scattering of an s-polarized wave by the same grating. A detailed comparison between the theoretical calculations and experimental measurements was performed. Strong localization of the scattered field near the edges of diffraction grating grooves was found. Such localization is very promising for numerous applications, e.g., biological sensors, optical tweezers for catching particles, or viruses, etc. [ABSTRACT FROM AUTHOR]

The electron-beam moiré method uses a high frequency grating to measure microscopic deformation. Increasingly fine gratings are being developed to achieve increasingly high resolutions in microscopic stress analysis. In this study, we improve the electron grid fabricating technique by using a common scanning electron microscope (SEM). An error analysis for the multi-scanning grating was performed by a sampling moiré method. The grating manufacturing parameters strongly affect the superfine grating quality. A high accelerating voltage or a short working distance yield better results generally. A set of optimal parameters is suggested based on a minimum-error criterion. A cross-line grid with a frequency of 10,000 lines/mm and a parallel grating with a frequency of 13,000 lines/mm were successfully fabricated. [ABSTRACT FROM AUTHOR]

Abstract: An adaptive optical limiter composed of nonlinear medium sandwiched between phase grating and one piece of slab is discussed under the circumstances of weak lights and intense laser pulses. The effects of refractive indices mismatch between phase grating and nonlinear medium on diffraction efficiency are investigated, which provides guidance for compounding nonlinear medium and evaluating limiting performance. [Copyright &y& Elsevier]

The optimization of photorefractivity (PR) based on a poly(N-vinylcarbazole) (PVCz) composite devise is proposed from the perspectives of chemistry and physics. The device's PR chemistry (dependence of PVCz's molecular weight) and physics (dependence of grating periodicity and laser wavelength) are studied. Increasing the molecular weight of PVCz from 23 000 to 1 270 000 g mol−1 significantly increases diffraction efficiency, grating build-up speed (inverse of response time), and sensitivity. Narrowing grating period from 5.1 to 1.1 μm gives faster response time and larger optical gain. Shorter wavelength of writing laser from 633 to 532 nm provides higher diffraction efficiency, faster response time, and larger optical gain. [ABSTRACT FROM AUTHOR]

It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. [ABSTRACT FROM AUTHOR]

In this article, a method for the fabrication of Ferroelectric liquid crystal switchable grating based on photo-alignment technique has been proposed. The first order diffraction efficiency is 86% and response time is 69 μs , which is 10 times faster than the existing switchable gratings. Maximum performance can be achieved at the electric field of 7V/μm. [ABSTRACT FROM AUTHOR]

In this paper, a novel automatic segmentation and reconstruction method is proposed for diffraction contrast tomography (DCT) technology. The pipeline of the proposed method starts from the imaging of Al−La alloy with the LabDCT technique from Carl Zeiss AG, which produces a sequence of 2D microstructure sections. Then, a segmentation algorithm based on superpixel and lifted multicut is proposed to extract the 2D microstructure in an image section. Finally, 2D segmentations are joined together to reconstruct and visualize the 3D microstructure. As a result, a novel morphology of Al−La alloy is recovered with both dendrite and lamellar morphologies. The proposed method has the advantage of the ability to losslessly recover the internal microstructure. [ABSTRACT FROM AUTHOR]

A simple diffraction experiment was designed using banana stem as natural grating. Coherent beams of lasers with wavelengths of 632.8 nm and 532 nm that pass through banana stem produce periodic diffraction patterns on a screen. The diffraction experiments were able to measure the distances between the slit of the banana stem, i.e. for a laser with a wavelength of 632.8 nm and for a wavelength of 532 nm. Therefore, banana stem could be used as an easily obtained and low cost grating for diffraction experiments. [ABSTRACT FROM AUTHOR]

We demonstrate twisted nematic liquid crystal (LC) polarization gratings (TNPGs) with a high first-order diffraction efficiency (>90%) that have the twist angle as constant, whereas the azimuthal angle of the mid-plane liquid-crystal director varies linearly in space. The high diffraction-efficiency design scheme is derived by means of the Jones matrix method. The designed first-order diffraction efficiency theoretically reaches 100% for the thick LC layer in which the retardation equals (n + 1/2)λ (n is an integer and λ is the wavelength). We also present a simple model for the grating period- and twist angle-dependent threshold voltage of the Freedericksz transition in TNPGs. [ABSTRACT FROM AUTHOR]