International Journal of

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.

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). 

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

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.

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.

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

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.

we investigate the temperature-dependences of the Brillouin frequency shift in three different kind of single-mode fibers using a heterodyne method for sensing temperature. Positive dependences coefficients of 0.77, 0.56 and 1.45MHz/0C are demonstrated for 25 km long single-mode fiber, 10 km long non-zero dispersion shifted fiber and 100 m photonic crystal fiber, respectively. The results indicate that microstructure fibers with a partially Ge-doped small core have great potential for fiber Brillouin distributed sensing.

Simultaneous laser induced- breakdown spectroscopy (LIBS) and acoustic response techniques as well as Laser induced fluorescence (LIF) are applied to investigate the abnormal lymph tissues due to Hodgkin disease. The spectral shift in the emissive fluorescence of the cancerous tissues has been observed respect to the normal ones. Regarding LIBS, the concentrations of Ca and Na trace elements have been identified to be higher in the cancerous samples. In addition, the acoustic response of cancerous tissues has been elevated against healthy ones. The distinct differences in the spectra are taken into account for early and the rapid identification and diagnosis.

Defocusing effects in modulation transfer function (MTF) measurement of charge coupled device (CCD) cameras is the main focus of current paper. We introduce measuring Point-spread function (PSF) in order to calculate the MTF and further more we will study the shape of MTF and its cut-off frequency by adjusting the lens focusing in different locations. A collimated white light LED by broadband spectra is used as source and our results shows that the cut-off frequency is related to defocusing.

Recently, we have demonstrated a new and efficient method to simultaneously reconstruct two unknown interfering wavefronts. A three-dimensional interference pattern was analyzed and then Zernike polynomials and the stochastic parallel gradient descent algorithm were used to expand and calculate wavefronts. In this paper, as one of the applications of this method, the reflected wavefronts from two surfaces of a spherical lens are experimentally reconstructed.

In this paper a novel anti-reflection (AR) coating based on silicon nano-bars is designed and its impact on the performance of crystalline silicon (c-Si) thin-film solar cells is extensively studied. Silicon nano-bars with optimized size and period are embedded on top of the active layer, under a 100nm Si₃N₄ layer. As a result of the proposed layer stack, an inhomogeneous intermediate layer with effective refractive index amid the two layers is formed and a graded refractive index AR coating is achieved, which has a substantial effect on broad, omnidirectional reduction of the reflection spectra. To validate our claim, the proposed structure as well as four conventional AR coatings are simulated and through the numerical analysis of both the spectral response of the reflection factor and the silicon active layer absorption spectra, it is shown that the proposed design outperforms conventional already existing AR coatings, and in addition provides a strong coupling of the incident light to the active layer, while improving the overall efficiency of the thin-film solar cell.

Experimental and theoretical absorption spectra of [2-[2-[4-(dimethylamino) phenyl]ethenyl]-6-methyl-4H- pyran-4-ylidene]-propanedinitrile (DCM) have been studied. UV-Visible (UV-Vis.) absorption spectrum of DCM has been reported after its synthesis. Two relatively intense peaks appeared at 473 and 362 nm respectively. A theoretical investigation on the electronic structure of DCM is presented in an effort to rationalize our experimental results. Theoretical results have been obtained with a polarizable continuum model time-dependent density functional theory (PCM-TD-DFT) approach. At first, a vast functional benchmark has been performed to determine a suitable approach for determination of electronic structure and UV-Vis. absorption spectrum of DCM. In a second step, we evaluated the impact of the atomic basis set on the electronic transition energies using a large panel of Pople’s basis sets ,up to the 6-31+G(3df,2p) and also a correlation consistent basis set, cc-pVTZ. It turns out that the selected basis set has a relatively finite influence on the calculated electronic transition energies as well as the topology of the absorption shape, but both are significantly affected by the chosen functional. In the present case, no single functional simultaneously provides highly accurate positions and intensities of the different bands, but mPW1PBE and mPW1LYP appear to be a good compromise. The mPW1PBE along with medium basis sets produced both absorption bands with maximum peaks about 463 and 346 nm. At all stages, ethanol has been chosen as a solvent environment. To improve the accuracy of first electronic excitation, a complete analysis of the origin of the band shape using TD-DFT vibrational couplings was performed. Finally the computed transition energy was corrected to 472 nm which was in excellent agreement with experiments.

In this paper, a Y-shaped power splitter based on a two dimensional photonic crystal (PhC) for TE modes is designed and optimized. A triangular lattice of air holes is used for Y-shaped power divider. For analyzing these structures, plane wave expansion (PWE) and finite difference time domain (FDTD) methods are used. The simulation results show that more than 98% of the input power is transmitted to the outputs and the structure has just less than 2% reflected power. According to the simulation results this structure is suitable for high bandwidth optical integrated circuit at the 1550 nm wavelength.

Compared to the long history of plasmonic gratings, there are only a few studies regarding the bandgap in the propagation of plasmonic surface waves. Considering the previous studies on interpretation of plasmonic bandgap formation, we discuss this phenomenon using the effect of both surface plasmon polariton (SPP) and localized surface plasmon (LSP) for our fabricated one-dimensional metallic-polymeric grating. This structure is composed of metallic grating on the surface of PDMS with different concentration of embedded gold nanoparticles. By sweeping the incident angles, we have seen that the SPP, LSP and their coupling cause two gaps in reflection regime which are originated from SPP supported by thin film gold film and LSP supported by gold nanoparticles. The first gap is attributed to the patterned metallic film because it vanishes by increasing the nanoparticles which may destroy the pattern while the second gap can be formed by embedded nanoparticles because it becomes more considerable by raising the incubation time. Therefore, the drowning time of patterned samples (e.g. 24h, 48h, and 72h) in HAuCl4 plays the key role in adjustability of plasmonic bandgap. Notably, the interaction between SPP and LSP can be the origin of the shift in gap center from 300 to 550. To best of over knowledge, this study is the first study on the plasmonic band gap as a function of both SPP and LSP.