Frequency encoded optical four-bit adder/subtractor with control input using semiconductor optical amplifiers

Optical adder/subtractor for two four-bit frequency encoded binary numbers are proposed and designed based on four wave mixing, add drop multiplexing and frequency conversion in semiconductor optical amplifier. The input bits and the control input are intensity-modulated signal of two specific frequencies suitable for optical communication in the C band of wavelength. The device can distinguish negative and positive results and controlled operation are most promising in this proposal. The use of semiconductor optical amplifiers along with frequency encoding makes the system very fast and useful for future optical communication and computation systems.     

Fast and slow light generated simultaneously for up-down-link frequency converter applications

We firstly propose a new system for simultaneous fast and slow light generation using a soliton pulse propagating within the nonlinear micro-ring resonators. The nonlinear Kerr effect induces the spreading frequency bands within the micro-ring device, where the chaotic filtering characteristics can be employed using the appropriate micro-ring parameters. Results obtained have shown that the wide spreading of frequency bands can be generated and selected to form the optical wireless communication links. In this work, the selected down-link and up-link frequency bands are 500 MHz and 2 GHz, respectively. The proposed system can be implemented within the mobile telephone hand set, where the two different frequency carriers within the same frequency bands can be selected to form the up-down-link converters, which means that the frequency converter can be performed within a single system.     

Position calculation of the frequency band gap in the finite photonic crystal with multiple alternations using boundary element method

In this paper, the wave transmission from finite photonic crystals with multiple alternations is investigated using boundary element method (BEM). Since that, in these structures the alternation is not in all directions of space; the investigations of the frequency band gap with desired accuracy are not practical by analytical methods. Also, the frequency dispersion of dielectric rods is an effective parameter in photonic crystals, which this effect in our calculations has been considered. Due to the high capabilities of the BEM, the transmitted wave spectrum in the photonic crystal is calculated by changing the geometrical and optical parameters of the photonic crystal and applying more alternation in its structure and the position and width of the frequency band gap is investigated. Then, it is assumed that the photonic crystal with an arbitrary angle is rotated around the axis which is perpendicular on the crystal cross section and then, it is irradiated with a plan wave. The band gap of the photonic crystals with the desired structure, desired rotation angle and multiple alternations have been solved. Very low information volume, high speed and accuracy during the calculation and useable for any desired structures are the characteristics of this method.     

Calculation of the frequency response in step-index plastic optical fibers using the time-dependent power flow equation

The time-dependent power flow equation, which is reduced to its time-independent counterpart is employed to calculate frequency response and bandwidth in addition to mode coupling and mode-dependent attenuation in a step-index plastic optical fiber. The frequency response is specified as a function of distance from the input fiber end. This is compared to reported measurements. Mode-dependent attenuation and mode dispersion and coupling are known to be strong in plastic optical fibers, leading to major implications for their frequency response in data transmission systems.     

Complete synchronization of Kuramoto oscillators with finite inertia

We present an approach based on Gronwall’s inequalities for the asymptotic complete phase-frequency synchronization of Kuramoto oscillators with finite inertia. For given finite inertia and coupling strength, we present admissible classes of initial configurations and natural frequency distributions, which lead to the complete phase-frequency synchronization asymptotically. For this, we explicitly identify invariant regions for the Kuramoto flow, and derive second-order Gronwall’s inequalities for the evolution of phase and frequency diameters. Our detailed time-decay estimates for phase and frequency diameters are independent of the number of oscillators. We also compare our analytical results with numerical simulations.     

Cr,Mo,Ni在α-Fe(C)中占位、键合性质及合金化效应的第一性原理研究

基于密度泛函理论第一性原理方法,采用广义梯度近似下的PW91泛函形式,计算了合金元素Cr,Mo,Ni固溶于α-Fe(C)的电子结构,从晶格畸变、结合能、态密度、重叠布居及差分电荷密度等计算结果出发探讨了合金元素在α-Fe(C)中占位、键合性质及其合金化效应,结果表明:Cr优先占据铁素体晶胞顶角位置,而Mo,Ni优先占据体心位置;Cr与晶胞的结合能最大,晶胞最稳定,Ni次之,Mo最低;Cr,Mo,Ni在晶胞中都存在金属键、共价键和微弱离子键的共同作用,成键轨道主要是Cr3d与Fe3d,Mo4d与Fe3d,Ni3d与Fe3d,C2p的交互作用形成的;Cr与晶胞原子间的键合作用强,晶胞的稳定性好,对增强钢材的机械性能帮助较大,Ni的键合作用较弱,但还是能保持晶胞的稳定性,Mo虽然键合作用强,但反键作用也非常强,使晶胞的稳定性大大降低,对钢材的机械性能危害较大.     

Diode-end-pumped composite Nd:YVO4 yellow laser based on intracavity frequency-doubled self-Raman laser

We report an intracavity frequency-doubled Q-switched self-Raman yellow laser at 587 nm. A composite Nd:YVO₄ crystal was utilized as self-Raman gain medium. The maximum average output power of yellow light obtained was 1.5 W at the incident pump power of 30 W and at a repetition rate of 50 kHz, corresponding to the optical conversion efficiency of 5%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 5.8 ns, 46.7 μJ and 5.9 kW, respectively.     

Frequency Domain Fluorescence Lifetime Study of Crude Petroleum Oils

Frequency domain (FD) fluorescence lifetime data was collected for a series of 20 crude petroleum oils using a 405 nm excitation source and over a spectral range of ~426 to ~650 nm. Average fluorescence lifetimes were calculated using three different models: discrete multi-exponential, Gaussian distribution, and Lorentzian distribution. Fitting the data to extract accurate average lifetimes using the various models proved easier and less time consuming for the FD data than with Time Correlated Single Photon Counting (TCSPC) methods however the analysis of confidence intervals to the computed average lifetimes proved cumbersome for both methods. The uncertainty in the average lifetime was generally larger for the discrete lifetime multi-exponential model when compared to the distribution-based models. For the lifetime distributions, the data from the light crude oils with long lifetimes generally fit to a single decay term. Heavier oils with shorter lifetimes required multiple decay terms. The actual value for the average lifetime is more dependant on the specific fitting model employed than the data acquisition method used. Correlations between average fluorescence lifetimes and physical and chemical parameters of the crude oils were made with a view to developing a quantitative model for predicting the gross chemical composition of crude oils. It was found that there was no significant benefit gained by using FD over TCSPC other than more rapid data analysis in the FD case. For the FD data the Gaussian distribution model for fluorescence lifetime gave the best correlations with chemical composition allowing a qualitative correlation to some bulk oil parameters.