International Journal of

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Layer-by-layer (LBL) electrostatic assembly of poly-electrolytes is proving to be an increasingly rich and versatile technique for the formation of multilayered thin films with a wide range of electrical, magnetic, and optical properties. In the present work we synthesized a new nonlinear optical (NLO) maleic acid copolymer containing Disperse Red 1 moieties, built-up multilayer assemblies by alternate adsorption of poly (allylamine hydrochloride) (PAH) and maleic copolymer derivative, and carried out an investigation on their second harmonic generation (SHG) properties. The resulting multilayer assemblies exhibit SHG which arises from the non-centrosymmetric alignment of the chromophore in the copolymer. The SHG signal increases with the number of chromophore-containing polymer layers, up to 5 layers. Further assembly reduces the signal

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Our recent advances in solid-state optoelectronic materials and devices will be reviewed. In the area of glass optics, fabrication of novel microstructured and multi-core fibers and their use in realizing single mode lasers will be summarized. In organic and plastic optics, photorefractive polymers for 3D display applications and nonlinear optical polymers for high speed modulators in RF photonic and remote antenna applications will be discussed. Our progress in medical optics including adaptive eyewear and imaging will also be described.

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In this paper we present an in-depth review on the trends and the directions taken by the researchers worldwide in Optical Code Division Multiple Access (OCDMA) systems. We highlight those trends and features that are believed to be essential to the successful introduction of various OCDMA techniques in communication systems and data networks in near future. In particular we begin by giving a comprehensive review on the constructions of optical orthogonal codes (OOC). In our system study we first focus and discuss on various OCDMA techniques such as 1-D, 2-D and spectrally-encoded ultrashort light pulse CDMA, and discuss their pros and cons. A comprehensive discussion takes place on all important aspects of each OCDMA technique. In particular, we elaborate on enabling technologies that are needed prior to full scale consideration of OCDMA in communication systems. We extend our discussion to various data networks, including fiber-based and wireless to indicate the directions and the applications that OCDMA systems are considered for. It is believed that OCDMA once fully developed and matured will be an inseparable part of advanced optical communication systems and networks due to its various desirable features and functionalities, in not so distant future.

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The distribution function of the electrons produced in the interaction between an intense electromagnetic wave and a neutral gas is derived and is shown to be nonequilibrium and anisotropic. By assuming that the time scale of gas ionization is much greater than the field period, it is shown that the electron distribution function formed in microwave and optical discharges has sharp anisotropy affecting the discharge plasma. The anisotropy stimulated by the inequality of average longitudinal and transverse energy of electrons is investigated. Furthermore, the parametric instability stimulated by scattering of incident wave on the density oscillation of plasma under the positive slope of EDF with respect to velocity is studied.

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CSs have been theoretically predicted and recently experimentally demonstrated in broad area, vertical cavity driven semiconductor lasers (VCSELs) slightly below the lasing threshold. Above threshold, the simple adiabatic elimination of the polarization variable is not correct, leading to oscillatory instabilities with a spuriously high critical wave-number. To achieve real insight on the complete dynamical problem, we study here the complete system of equations and find regimes where a Hopf instability, typical of lasers above threshold, affects the lower intensity branch of the homogeneous steady state, while the higher intensity branch is unstable due to a Turing instability. Numerical results obtained by direct integration of the dynamical equations show that writable/erasable CSs are possible in this regime, sitting on unstable background

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Solid-state Raman lasers are known as important sources at normally difficult to access wavelengths, and our recent studies have shown that they also form the basis of a class of wavelength selectable lasers. This paper summarizes our recent studies in wavelength selectable Raman lasers in the visible (532-650 nm) and ultraviolet (266-321 nm). 

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In this paper, by considering a system consisting of a single two-level trapped ion interacting with a single-mode quantized radiation field inside a lossless cavity, the temporal evolution of the ionic and the cavity-field quantum statistical properties including photon-counting statistics, quantum fluctuations of the field quadratures and quantum fluctuations of the ionic dipole variables are investigated. It is found that in the Lamb-Dicke limit it is possible for the cavity-field to evolve into a nonclassical state (squeezed state or state with sub-Poissonian statistics) and this possibility is solely affected by the internal and external quantum dynamics of the ion. Also it is found that the dipole squeezing may occur in the dynamics of the trapped ion which sensitively depends on quantum statistics of the cavity-field.

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In this paper, we present a comparative numerical analysis to determine the refractive index of photonic crystal fibers (PCFs) by using FDFD method and used the results to evaluate the confinement losses of PCFs by considering the effects of air-hole rings in the cladding. It is shown that by increasing the wavelength, the imaginary part of refraction index rises, resulting in increase of confinement losses nearly by order of 10. In lower wavelengths over the range of 0.2 to 1 μm, these losses were shown to be negligible. The obtained results show that as the number of air-hole ring in the cladding increases, the confinement losses over wavelengths would reduce. To show the effect of air-hole rings on confinement losses in PCFs, the FDFD method yielded accurate results that agree well with results of FEM method and source–model technique reported by others.

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In this paper we consider electromagnetic field quantization in the presence of a dispersive and absorbing semiconductor quantum dot. By using macroscopic approach and Green's function method, quantization of electromagnetic field is investigated. Interaction of a two-level atom , which is doped in a semiconductor quantum dot, with the quantized field is considered and its spontaneous emission rate is calculated. Comparing with the same condition for an excited atom inside the bulk, it is shown that the spontaneous emission rate of an atom will decrease.

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This paper describes the passive Qswitch, based on polymer and organic dye BDN, of a pulsed Nd:YAG laser. Pulses of 27ns duration and peak power of 1.7MW for initial transmission of Q-switch 18.4% 0 T = have been obtained. We have obtained Q-switching efficiency of 77% for train of pulses of 31 and 76.2% 0 T = at the pump energy of 98J. We have also obtained the dependency of laser pulse characteristics on pump energy and initial transmission of Q-switch. We have obtained the damage threshold of this Q-switch at the pulse duration of 27ns to be13J cm2 .

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Electronic absorption, florescence excitation and AFM studies of selected homogeneous solutions and thin films of mesotetrakis (parahydroxyphenyl) porphyrin (THPP) (1), mesotetrakis (2, 3- dihydroxyphenyl) porphyrin 2, 3-OHPP) (2), mesotetrakis (3, 4-dihydroxyphenyl) porphyrin (3, 4-OHPP) (3) as well as Zn(II) derivative of 2, 3-OHPP (4) under UV lamp and green laser irradiation (532 nm) are acquired and analyzed.Our results indicate that in irradiation experiments, the products of the resulting porphyrins strongly depend on the careful choice of the light source. UV lamp irradiation produced J-type aggregated diacid porphyrins from free base porphyrins by simple photochemical technique. The stabilization of the aggregates structure may be achieved through hydrogen bonding between the protonated core and the peripheral hydroxyl groups, mediated by the chloride anions. The results of laser irradiation experiments shown the formation of J-aggregated porphyrin upon green laser (532 nm) irradiation.Green laser irradiation has been caused the hydrogen bonding interactions between neighboring porphyrin molecules through hydroxyl moieties to produce J-aggregated supramolecular porphyrins. The AFM topographic images and Dynamic Light Scattering (DLS) of THPP(1) under green laser irradiation have been indicated nano-structured porphyrin wires about 5 nm high approximately.

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In this work, using perturbation technique we have developed an approximate analytic model for evaluating the band structure of a 2-D octagonal photonic quasicrystal (PQC). Although numerical techniques are being used for evaluating such band structures, developing a numerical model to the best of our knowledge this work is the first instance of reporting helps to understand the physical properties of the structure more easily. Use of perturbation technique can be beneficial in approximating the photonic band structures, in PQCs made with low-dielectric contrast materials, with high accuracy. To the best of our knowledge this work is the first instance of reporting the development of such an analytic model for octagonal PQCs. In addition, we have studied the effect of variations in the dielectric contrast on the photonic band structure.

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In this paper, a brief summary of different methods of fabrication of optical preform and fiber is reviewed. Several methods of incorporation of erbium ions into optical preforms are studied. Characterization of the fabricated erbium doped fibers including measurements of refractive index profile, absorption, fluorescence and gain spectra and metastable lifetime are described. It is also expressed that many of these fabrication and characterization methods are feasible to be carried out in Iran.

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The average velocity of water flow has been simultaneously measured with fluorescent and speckle imaging methods. The measured velocities with two methods are in good agreement with each other and it confirms that the speckle imaging method can be used as a confident method to measure the velocity of water flow in a dry leaf. Also the velocity of water flow through thick and thin xylems of a leaf can be measured with speckle imaging method and the ratio of thick xylem’s radius to thin xylem’s radius can be estimated with this method. Also the ratio was measured by monitoring the cross section of the leaf. The two measurements were in agreement.

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We generalized the squeeze and displacement operators of the one-dimensional harmonic oscillator to the three-dimensional case and based on these operators we construct the corresponding coherent and squeezed states. We have also calculated the Wigner function for the three-dimensional harmonic oscillator and from the analysis of time evolution of this function, the quantum Liouville equation is also presented. Further properties of the quantum states including Mandel’s 􀡽 and quadrature squeezing parameters are discussed as well.

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We have studied light-induced birefringence (LIB) and surface relief grating (SRG) formation in the series of methylacrylate polymers. The effect of material structure such as length of photochromic side chain, glass transition temperature and molecular structure of azo units on LIB and SRG are studied. The optical formation of self-induced SRG on films of these materials is also presented.

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In this paper, by including Raman scattering in the coupled-mode equations, the scalar modulation instability in photonic crystal fibers is investigated. The evolution of the pump, Stokes and anti-Stokes waves along the fiber as well as the conversion efficiency for two cases, with and without Raman effect, are studied. The effect of anti-Stokes seed and the pump depletion on the evolution of Stokes wave is also considered. Moreover, the parametric gain when it is affected by Raman gain is dealt with. The results show that it is important to take into account Raman scattering, especially for wide-bandwidth parametric amplifiers which results in an asymmetric spectrum and more amplification of the Stokes wave.

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We proposed and analyzed implementation of the single-qutrit quantum gates based on stimulated Raman adiabatic passage (STIRAP) between magnetic sublevels in atoms coupled by pulsed laser fields. This technique requires only the control of the relative phase of the driving fields but do not involve any dynamical or geometrical phases, which make it independent of the other interaction details: detuning and pulse shapes, areas and durations. The suggested techniques are immune to spontaneous emission since the qubit and qutrit manipulation proceeds through non-absorbing dark states. In this paper, taking proper timing of the Rabi frequencies allows us to transfer the population of the system to a desired superposition of the ground states with the highest fidelity. We also obtained and implemented single-qutrit unitary gates, for transferring of the population of the system with different initial and final states.

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The refraction phenomenon at the interface of an ordinary material and a lossy metamaterial has been investigated. For oblique incidence on the lossy metamaterial, the planes of constant amplitude of the refracted wave are parallel to the interface and the plane of constant phases make a real angle with the interface (real refraction angle). The real refraction angle and hence, the real refraction index corresponds to the real refraction angle which satisfies the real version of Snell's law are negative in two different regimes. In one regime, the metamaterial is double-negative, while in the other one it is single-negative. Moreover, we show that the plane wave solution for the refracted wave is causal in both double-negative and single-negative regimes

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Europium doped transparent lead fluorophosphate glass ceramics successfully were prepared with heat treatment of precourse glasses at temperature above glass transition (Tg). X-ray diffraction (XRD) experiment evidenced the formation of PbF2 nanocrystals in glassy matrix. The emission spectra investigation indicate that considerable amount of Eu3+ ions were trapped in crystalline phase, and therefore the efficient frequency-conversion was observed in glass ceramics samples. The investigated glass ceramics systems are potentially applicable as up and down frequency-conversion photonics materials.