All optical logic gates based on an asymmetric nonlinear directional coupler

The performance of three different asymmetric dual core nonlinear directional couplers which includes an increasing and a decreasing self-phase modulation profile (SPM) was investigated. The asymmetry is associated to the SPM profile of one of the channels. Looking at the transmission characteristics of the device, through the direct- and cross-channel, we did a study of the extinction ratio (Xratio) of the devices. It was observed that in the operation of the three couplers, the performance of AND, XOR and OR gates are dependent on the nonlinearity profile of the coupler. For all configurations, an AND port with gain was observed. We can conclude that to operate the asymmetric coupler as a logic gate one has to control the nonlinearity profile to optimize the transmission characteristics thorough the extinction rate coefficient (Xratio).     

基于高非线性光纤中非线性偏振旋转效应的全光逻辑门研究

提出了一种新型的基于高非线性光纤(HNLF)中非线性 偏振旋转(NPR)效应的全光逻辑门实现方案. 将两路非归零码数据信号A和B以及一路直流光同时注入HNLF, 光功率变化导致的非线性双折射在两个偏振分量上引入非线性相对相移, 从而导致光信号的偏振态旋转. 在HNLF输出端, 通过波分解复用器和偏振分束器同时滤出数据信号和直流光的正交偏振态, 从而同时实现多种基础组合逻辑, 并可以在同一段HNLF中实现较为复杂的半加器、半减器逻辑功能. 理论分析了信号光在HNLF中的偏振态演化, 以及利用HNLF中的NPR效应同时实现多种全光逻辑门的原理. 并在实验中得到了10 Gbit/s全光信号"与”、"非”、"或”、"同或”、"异或”、"A· B”、"A·B”、半加器、半减器等逻辑功能, 验证了方案的可行性.     

All optical method of developing OR and NAND logic system based on nonlinear optical fiber couplers

Logic gates are the fundamental building blocks in any digital data processing system. Several all optical logic operations are already proposed by scientists and technologists. Here the authors proposed a new method of all optical logic operation based on nonlinear directional coupler. Effective optical switching is achieved by modifying the coupling length between the coupler waveguides by means of an optical signal.     

Ultrasmall optical logic gates based on silicon periodic dielectric waveguides

An ultrasmall silicon periodic dielectric waveguides-based multimode interference all-optical logic gate has been proposed. The device consists of three 205 nm wide single-mode input waveguides, a 1.1 μm wide and 5.5 μm long multimode interference waveguide, and three 205 nm wide single-mode output waveguides. The total length and width of the device are 13.7 μm and 3.2 μm, respectively. By changing the states of the input optical signals and/or control signals launched into the device, multifunctional logic functions including OR, NAND, NOR, and NOT gates are performed, and each logic function can be realized at a specific output waveguide in accordance with the launched control signals. The ultrasmall multifunctional logic device has potential applications in high density photonic integrated circuits.     

Computational analysis of solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers

Solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers-assisted Mach–Zehnder interferometers are computationally analyzed at a data rate of 80 Gb/s. The investigation of the output quality factor is included. All-optical logic gates are capable of operating at 80 Gb/s with logical correctness and acceptable quality.     

All optical alternative approach of conducting NAND and NOR logic gates with phase encoding principle

All optical logic gates are the most important building blocks for conducting all optical digital and analog signal processing and computing. It has several uses in the high speed communication system. In last few years various non-linear properties of semiconductor optical amplifier have been utilized for realization of all optical logic gates exploiting different type's optical modulations. In such connection optical phase encoding technique drew more attention in last few years as it shows higher receiver sensitivity and extended tolerance limit in long-haul fiber transmission systems. In this communication the authors have proposed an alternative approach for conducting all optical logic gates with phase encoded inputs by the exploitation of the four wave mixing (FWM) property in semiconductor optical amplifier (SOA).     

基于单个半导体光放大器的高速多功能逻辑门

采用半导体光放大器(SOA)中的非线性效应可以实现多种多样的高速全光信号处理. 利用SOA的非线性效应(包括四波混频、交叉增益调制、瞬态交叉相位调制等)实现了多种功能的逻辑运算,包括“与”、“或非”、“同或”、“或”和“非”. 由于SOA用于全光信号处理的调制速率受到增益恢复时间较慢的限制而无法实现高速的信号处理,在SOA后面级联一个带宽为0.32nm的失谐滤波器可以提高SOA的工作速率,仅用一个SOA实现了40Gbit/s的多功能逻辑门. 关键词： 半导体光放大器 全光逻辑门 瞬态交叉相位调制     

All-optical logic gates based on two-photon absorption in semiconductor optical amplifiers

When the two-photon absorption of a high intensity pump beam takes place in a semiconductor optical amplifier there is an associated fast phase change of a weak probe signal. A scheme to realize fast all-optical XOR logic function using two-photon absorption induced phase change has been analyzed. Rate equations for semiconductor optical amplifiers, for input data signals with high intensity, configured in the form of a Mach–Zehnder interferometer has been solved. The input intensities are high enough so that the two-photon induced phase change is larger than the regular gain induced phase change. The model shows that both XOR operation and pseudo-random binary sequence generation at 250 Gb/s with good signal to noise ratio is feasible.     

基于细菌视紫红质光子逻辑门的实验研究

研究了基于细菌视紫红质(简称BR或菌紫质)变种材料D96N的3种光逻辑操作.在633nm激发光照射下，菌紫质分子会被激发到M态，处于M态的菌紫质对412nm的紫光呈较大吸收，会抑制同时入射的紫光.选择合适的紫光强度，通过CCD观测被抑制的412nm检测光透射强度分布，模拟了“非”、“或非”、“与非”几种基本的光子逻辑操作. 关键词： 细菌视紫红质 光子逻辑门 互补抑制     

All optical quasi-steady-state photorefractive spatial solitons

We have created a one- (rather than two-) dimensional quasi-steady-state photorefractive spatial soliton induced by a laser beam instead of an applied electric field. The formation of this type of spatial soliton depends on the intensity of the self-trapped beam, which is different from quasi-steady-state spatial solitons reported in the literature. The optically induced spatial soliton can be exploited in all optical switching applications.     

All optical logic NAND gate based on two-photon absorption in semiconductor optical amplifiers

We propose a new scheme to realize all optical logic NAND operating at high speeds up to 250 Gb/s utilizing the ultrafast phase response during two-photon absorption (TPA) process in semiconductor optical amplifiers (SOA). NAND gate is important because other Boolean logic elements and circuits can be realized using NAND gates as basic building blocks. Rate equations for semiconductor optical amplifiers (for input data signals with high intensity) configured in the form of a Mach-Zehnder interferometer have been solved. The input intensities are high enough so that the two-photon induced phase change is larger than the regular gain induced phase change. The performance of this scheme is analyzed by calculating the quality factor of the resulting data streams. The results show that both AND and NAND operations at 250 Gb/s with good signal to noise ratio are feasible.     

The effect of nonlinear gain on the characteristics of an optically injected VCSEL and cavity solitons

Using the Lagrange method to fit the curve of maximum gain as a function of carrier density for an active region consisting of an AlGaAs/GaAs layers sandwiched between DBR layers, it is found that the curve is better approximated assuming a quadratic dependence on the carrier density. By summarizing all of the calculations into a nonlinear gain coefficient parameter, $\beta $ , in the Maxwell–Bloch equations we numerically studied the effect of nonlinear gain on the characteristics of the VCSEL and also on the cavity solitons (CSs) forming in such a device. Particularly, it is shown that with nonlinear gain a wider locked region can be achieved along with enhanced sustained relaxation oscillation amplitude. The switching on/off time of CSs is modified and there appears a considerable enhancement in their efficiency and contrast.     

Dissipative solitons in a waveguide with nonlinear gain and absorption

The results of numerical analysis of dissipative localized structures (“dissitons”) in a single-mode waveguide with nonlinear gain and absorption are presented. An allowance is made for the finite relaxation times in the active and passive media and the finite width of the spectral profiles of absorption and gain.     

Implementation of tristate logic based all optical flip-flop with nonlinear material

The advantages of multivalued logic in optical parallel computation need no introduction. There are lots of proposals, already reported, where tristate, quarternary state logic operations can be performed with optics. Here we report a new approach to implement tristate logic based all optical flip-flop using optical nonlinear material. The concept and the principle of operation of this type of flip-flop are different from that of the conventional binary one.     

Logic gates based in two- and three-modes nonlinear optical fiber couplers

In this paper we did a study of logic gates obtained in the operation of a three-core non linear directional coupler (TNLDC) and an asymmetric two-core coupler (DNLDC) operating in the CW regime (the laser signals have the same wavelength). The symmetric three-core coupler (TNLDC), with their cores identical, in a planar arrangement, was studied using a control pulse applied to the first core. The second structure is an asymmetric two-core coupler (DNLDC). Looking at the transmission characteristics of the device, through the direct and cross channel, we did a study of the extinction ratio (Xratio) of these devices. For both devices we did a numerical investigation with the objective to implement logic gates. The DNLDC supplied AND, OR and XOR gates while the TNLDC supplied AND, NAND, OR, XOR and NOT gates. In comparing the performance of both switches operating as logic gates (DNLDC and TNLDC) we define, for the first time, a figure-of-merit of the logic gates (FOMELG). In this criteria the FOMELG is defined as a function of the extinction ratio of the gate outputs. Comparing the same gates of the three and two-core NLDC we observe that the logical gates of the three-core TNLDC present a better performance than the one of the two-core DNLDC considering the figure of merit FOMELG, besides the fact that is simpler to fabricate a symmetrical coupler (with identical cores) comparing with an asymmetric coupler. We believe that the use of this figure of merit will be useful in the study of the performance of logic gates to be used in communication systems.     

Bloch cavity solitons in nonlinear resonators with intracavity photonic crystals

We predict a novel type of cavity solitons, Bloch cavity solitons, existing in nonlinear resonators with the refractive index modulated in both longitudinal and transverse directions and for both focusing (at normal diffraction) and defocusing (at anomalous diffraction) nonlinearities. We develop a modified mean-field theory and analyze the properties of these novel cavity solitons demonstrating, in particular, their substantial narrowing in the zero-diffraction regime.     

基于半导体材料微纳波导全光逻辑门的研究进展

全光逻辑门是全光计算以及全光信号处理系统中关键的光子器件.随着互补金属氧化物半导体(COMS)工艺的发展,基于半导体材料微纳波导全光逻辑门已经成为集成光学领域中的重要方向;尤其是硅基光子集成器件在近些年成为了国际研究热点.文章主要对基于绝缘体上的硅(SOD)和Ⅲ-Ⅴ族化合物材料不同波导结构(马赫-曾德尔干涉仪(Mach-Zehnder interferometer)微环谐振腔和条形波导结构)的全光逻辑门的研究进展进行了介绍,并且在器件的工作速率和功耗方面,分别对上述基于SOI和Ⅲ-Ⅴ族化合物材料三种不同波导结构的全光逻辑门进行了分析和比较.     

Two-photon cavity solitons in active optical media

We show that broad-area cascade lasers with no absorbing intracavity elements support the spontaneous formation of two-dimensional bright localized structures in a dark background. These cavity solitons consist of islands of two-photon emission embedded in a background of single-photon emission. We discuss the mechanisms through which these structures are formed and interact, along with their properties and stability.     

基于半导体材料微纳波导全光逻辑门的研究进展

全光逻辑门是全光计算以及全光信号处理系统中关键的光子器件.随着互补金属氧化物半导体(CMOS)工艺的发展,基于半导体材料微纳波导全光逻辑门已经成为集成光学领域中的重要方向;尤其是硅基光子集成器件在近些年成为了国际研究热点.文章主要对基于绝缘体上的硅(SOI)和Ⅲ-Ⅴ族化合物材料不同波导结构（马赫-曾德尔干涉仪(Mach-Zehnder interferometer)微环谐振腔和条形波导结构）的全光逻辑门的研究进展进行了介绍,并且在器件的工作速率和功耗方面,分别对上述基于SOI和Ⅲ-Ⅴ族化合物材料三种不同波导结构的全光逻辑门进行了分析和比较.