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Abstract- Zinc oxide coating was grown using on Si(111) by electrodeposition. Crystalline structure,optical and morphological properties were studied using X-ray diffraction (XRD), reflectance spectrum and scanning electron microscopy (SEM), respectively.Hexa-gonal wurtzite nanocrystalline structure was grown with random orientation. Surface morphology shows the effect of deposition time on shape and size of grown structures. As deposition time increase, the formed structure stretched in one dimension, furthermore, three-dimensional growth overwhelms. The quantum confinement effect and band filling have been discussed on optical band gap widening from 3.21eV to 3.70eV.

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Optical tweezers is one of the most effective methods for manipulating micron and sub-micron sized particles non- destructively. In this paper a tapered fiber optical tweezers is calibrated using power spectrum analysis of the trapped particle motions. We utilized a high- speed CMOS camera with 500 frames per second for particle position detection. As validation experiment, using this setup, stretching of a multilamellar lipid bilayers is demonstrated.

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In this paper the optical properties of a weak probe field in a duplicated two-level (DTL) system are investigated beyond multi-photon resonance (MPR) condition. The group velocity of light pulse can be controlled by the intensity of applied fields and the gain-assisted superluminal light propagation is obtained in this system. Moreover, the group velocity can be controlled by incoherent pumping rate.

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We propose a method to increase resolution of a Fresnel zone plate by modulating Fresnel zones .In this method, Fresnel zones plate is divided into zones with different widths that each zone include an open ring. Then the open rings are replaced by a give distribution of pinholes which leads to modified photon sieve .Its focusing properties are broadly investigated by simulation and verified by experiments. Resolution of this lens is modified well as well as the Secondary foci are suppressed.

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In this paper, the photon sieve designed is divided into regions, each of which includes holes with different widths. We demonstrate that the foci locations change by the varying the number of the holes in each area. This method can be achieved to a lens with double focusing properties. By applying this method also, the radius of the lens and resolution are increased. Simulation results are verified by experiments.

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Interferometric microscopes are one of the most effective methods in study of micron and sub-micron sized samples including biological cells. Among the different interferometric methods, digital holographic microscopy (DHM) has a significant importance in studying the dynamics of moving samples. Recently the utilization of common-path geometries has been popular for studying the cell fluctuations because of high temporal stability and low optical path difference (OPD) difference. In this paper we present a compact, efficient and highly stable setup during each kind of mechanical, optical and environmental vibrations based on Fresnel biprism interferometry. A Diode Laser module with low coherence length was used as the source. Reconstructing the intensity and phase information is possible by using fringe analysis methods. We measured OPD variations vs. time by this configuration and compared the results with an off-axis DHM setup based on Mach-Zehnder interferometer geometry. The results illustrated the great performance and nanometer accuracy of our setup in studying the morphological changes of living cells

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In this paper, a method based on Fresnel diffraction from a parallel phase plate is presented for the phase study of micron- sized transparent samples. If a transparent plate is located in the path of a monochromatic beam of laser light, the diffraction fringes appear due to an abrupt change in the optical path length (OPL) difference between the part of the incoming light passing through the plate and the other propagating in the air. Now, if another phase sample is located in the path of the incoming light to the plate, the diffraction fringe pattern changes. the phase information of the sample can be extracted within the fringes by different fringe analysis methods. The presented setup is simple in comparison with complex interferometry techniques and the fringe pattern is stable against any mechanical and optical vibrations. Also, the accuracy of phase measurement is comparable with other common methods in which anti-vibration tables and high precision optical elements are required. By using this method, some measurements are performed on Red Blood Cells (RBC) and the results are compared with digital holographic microscopy (DHM) technique. The results indicate the high efficiency of technique in study of microscopic samples and nanometric variations in the membrane of living cells

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Optical imaging through turbid and scattering layers is a challenge in optical microscopy. The light passing through the inhomogeneous samples including biological cells is scattered and speckle pattern appears. In this paper, a method is introduced based on Fourier-domain shower-curtain effect for imaging of objects and resolution enhancement of the recorded images in scattering media. The information of the object can be reconstructed from the autocorrelation of speckle patterns by a phase retrieval algorithm.

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We have designed an ultrathin metamaterial absorber which is capable of total absorption of the incident electromagnetic waves in the terahertz regime. Results demonstrate that the absorber is sensitive to the polarization and can operate at a wide range of incident angles under both transverse electric (TE) and transverse magnetic (TM) polarizations. The absorbance for s-polarized (TE) and p-polarized (TM) waves are 99.14% at 8.14 THz and 96.45% at 5.95 THz, respectively. The absorption frequency can be dynamically tuned by the geometries of the absorber. This terahertz metamaterial structure can be used in novel THz applications such as polarization detectors, polarization imaging, THz sensing, and polarization multiplexing.

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In this paper zinc oxide sheets are grown on a FTO substrate using electrochemical method. The nonlinear optical coefficients of these sheets are determined using the z-scan technique. In this method, a cw Nd-YAG laser with wavelength of 532 nm is applied as the radiation source. Our experimental results indicate that the ZnO sheets have positive nonlinear refractive index and exhibit the nonlinear self-focusing phenomenon. Furthermore, the z-scan results reveal that ZnO sheets grown in this paper possess saturated absorption. Finally, the third order nonlinear susceptibility is obtained for ZnO sheets by using the measured nonlinear refractive index and nonlinear absorption coefficient.        
 

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In this paper we have investigated the nonlinear optical and optical limiting properties of suspensions of Graphene oxide nanoparticles in both water and ethanol environments. Using a low power laser diode at a 532 nm wavelength, the nonlinear absorption was determined by an open aperture Z-scan technique. Results showed that graphene oxide dispersed in water and in continuous regime does not exhibit significant nonlinear absorption properties. While on the other hand, graphene oxide dispersed in ethanol shows high nonlinear absorption properties. The optical limiting effect of these samples were also investigated using the 2nd harmonics of a pulsed Nd-YAG laser at 532 nm. As it was predictable from our results in continuous regime, Graphene oxide nanoparticles that were dispersed in ethanol had higher limiting properties compared to the other sample which was dispersed in water.

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In this paper, a periodic array of Silver spherical-nanoparticles is considered to act as a tunable plasmonic filter in telecommunication window, in which, the array is embedded by a layer of Germanium and set on the silicon dioxide substrate. The purpose of this material configuration is to increase the local fiend between adjacent nanoparticle and Ge layer which in turn increases the absorption of optical fields by nanoparticles in array. Illumination at infrared region excites localized surface plasmons (LSPRs) of silver nanoparticles and due to the hybridization between these nanoparticles in array, the resonance frequency LSPRs red-shifts to telecommunication window. Coupling between LSPRs and incident field leads to confining optical field at the gap distance between nanoparticles and improves the quality of filtering at telecommunication window in the terms of optical absorption at the wavelength of interest. Finite difference time domain (FDTD) method have been used to both calculate filtering spectra and local field between adjacent nanoparticles. Also, the effect of size parameters of nanoparticles on quality of optical confinement and filtering spectra have been studied.

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We have investigated nonlinear optical properties of blood serum using a continuous wave laser at a wavelength of 532 nm. Utilizing open and close aperture of a Z-scan technique enables a measurement of the nonlinear refractive index of blood serum . Our results show that  increases because of increasing of the glucose content when the iron content is constant. We measured the refractive index of this serum using Sheik-Bahae’s and Z-scan models.

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In this paper, Nd:YAG pulsed laser design with Slab geometry based on MOPA structure is discussed. To Reduce the Thermal effects and increase the quality of the laser output beam, Slab geometry is used in amplifier stage. The Energy amplification, has been calculated in slab geometry with Franz-Nodvik equation. In the amplifier stages, two stage with dimensions of 138.5×35×7 mm has been used. For 20 mj input energy and  4J pump power to each amplifier stage, the Output energy was obtained 5J.

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The problem of coherent light diffraction from a rectangular aperture in an opaque screen is well formulated in the undergraduate physics textbooks using scalar diffraction theory, and the results of these calculations have long been tested in optics labs and are used for educational and research purposes such as various measurements (for example, the size of a particles). In recent years, Iranian researchers have introduced new options for creating and applying the diffraction phenomenon in accurate measurements, which is the light diffraction from steps created on a reflective surface and diffraction from the edges of transparent objects. In this paper, we study the phenomenon of coherent light diffraction from a rectangular phase strip (slit), calculate the scattered light intensity distribution, and present computational and experimental results. We show that in this case, the usual formulas for measuring the width of the slit cannot be used. Examination of this type of diffraction can be used to measure the dimensions of transparent objects (for example, glass fibers or transparent organisms and particles under a microscope).

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In this paper, the advantages of using concentric circular diffraction grating with equal spaces compared to linear diffraction grating in smartphone-based methods are investigated. Their image-formation properties are described, and we examine the effects of linear and circular diffraction grating aberrations for spectrometer-based smartphones. Data collection is done by the smartphone camera, so we need to have the image with the least amount of aberration and the highest image quality. With circular diffraction gratings, the curvature of the field, the distortion aberration, and the wavefront aberration are reduced. Therefore, the most suitable system for making this type of spectrometer is the use of circular diffraction gratings.