基于半导体激光器的全光波长转换的理论研究

全光波长转换是全光网络的关键技术之一。利用多模半导体激光器的速率方程,建立了基于半导体激光器的全光波长转换器的理论模型,该模型不仅考虑了注入信号光对激光腔内载流子的消耗,而且考虑了激光腔对注入信号光的放大作用。利用该模型分析了半导体激光器工作电流、注入信号光功率以及码率各参数对波长转换特性的影响。结果对于确定基于半导体激光器的全光波长转换器件的最佳工作条件有一定的参考价值。     

表面等离子体激元纳米集成光子器件

纳米集成光子学的核心关键技术之一在于新型高效纳米光耦合器、纳米光波导等纳米光子器件的设计与制备.表面等离子体激元（SPPs）是由外部电磁场与金属表面自由电子相互作用形成的一种相干共振,除具有巨大的局部场增强效应外,还具有将激发电磁场能量限制在纳米尺度范围的特点.基于SPPs的各种纳米光子器件被誉为当今最有希望的纳米全光集成回路的基础,成为目前国际上的一个研究热点.文章对基于SPPs的纳米集成光子器件的最新研究进展和研究成果进行评述。     

科学家成功研制出由单光子控制的全光晶体管

近日消息,美国麻省理工学院（MIT）电子研究实验室（RLE）、哈佛大学以及奥地利维也纳技术大学的科学家们在最新一期《科学》杂志公布,研制出了一种由单个光子控制的全光开关,新的全光晶体管有望让传统计算机和量子计算机都能受益。全光开关的核心部件是一对高反光镜。当打开开关时,光信号透过两面镜子,当关闭开关时,只有20％的光信号透过镜子。如此一来,这对镜子就构成了所谓的光学共振器。该研究的领导者、MIT物理学教授弗拉达·乌勒提解释道,如果根据光的波长精确地调整镜子间的距离,那么,对某些波长的光来说,镜子就是透明的,这就是默认的“开”状态。     

掺半导体玻璃波导光栅耦合高速全光开关

非线性光学器件的主要应用目的之一是全光信号处理,非线性光波导象其它非线性光学器件一样,也已被广泛地应用于全光信号处理方面的研究,如人们已采用棱镜波导非线性分布耦合方式来实现全光限幅、全光开关和全光双稳等研究[1,2].在非线性光波导器件中,由于光被束缚在微米尺寸的光波导中传输,而大大增加了光功率密度,因此,在光与非线性光波导的相互作用过程中可以大幅度地降低非线性效应的阈值功率,提高全光信号处理的灵敏度.此外,非线性光波导器件的小型化、集成化等优点更吸引人们去进行深入的研究.     

半导体光放大器的光-光互作用及其应用

半导体光放大器（SOA）中的非线性系数约为普通光纤的10^9，为光子晶体光纤的10^7，而且有4种光-光互作用，即交叉增益调制（XGM）、交叉相位调制（XPM）、交叉偏振调制（XSM）及四波混频（FWM），可以灵活地组成各种光信号处理器件，如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器……等，正成为整个光信号处理的基础。文章介绍了它们的原理和简单应用。     

光梯度力驱动的纳米硅基光开关

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标, 然而, 由于硅材料的光学非线性较弱, 在硅材料上实现开关的全光控制难以实现. 因此本文提出了一种由光梯度力驱动的纳米硅基光开关, 实现了硅基光开关的全光控制. 该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成, 当通入一道控制光时, 悬空的微环谐振器在光梯度力的作用下发生弯曲, 微环谐振器的谐振波长随之发生变化, 从而实现光信号的传输路线发生改变. 该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造, 实验数据得出其最小消光比为10.67 dB, 最大串扰为 -11.01 dB, 开关时间分别为180 ns和170 ns. 该光开关具有尺寸小, 响应速度快, 低损耗和可拓展等优点, 在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.     

低功耗非线性光纤光栅全光开关

全光开关是未来全光通信和光计算机的关键器件.已经研究过的全光开关的种类很多,其中光纤光栅全光开关最容易与光纤系统匹配.文章首先陈述两种基于普通石英光纤的单光栅全光开关,即光纤布拉格光栅(FBG)全光开关和长周期光纤光栅(LPFG)全光开关,这两种低非线性的光开关要求千瓦量级的高开关功率,故不宜应用;然后重点介绍两种高非线性的光纤光栅全光开关,它们分别由单个高非线性FBG和用高非线性光纤连接的LPFG对构成.文章所介绍的非线性光纤材料是以掺稀土石英光纤为例.这两种高非线性的光纤光栅全光开关具有毫瓦量级的低开关功率,有可能获得实际应用.     

级联二阶非线性铌酸锂全光开关的研制

以基于准位相匹配和频与差频级联二阶非线性[X^(2)：X^(2)]基础上的全光开关的理论分析作指导,进行了周期极化铌酸锂晶体(PPLN)和退火质子交换光波导(APE)的实验制备,利用所研制的PPLN-APE器件,以自行研制的工作波长为1．54μm的被动调Q掺钴铝酸镁激光器作为控制光源,以工作波长为1．5μm的连续二极管激光器为信号光源进行了级联二阶非线性全光开关实验。当控制光峰值功率为3kw,信号光功率为1mW时,实现13％的开关效率,分析了进一步提高全光开关性能的途径。     

ZnO一维纳米线及其异质结构的外延生长

一维纳米结构因其优异的光、电特性，在纳米电子学，光电子学器件等方面有重要的应用价值而倍受关注．在一维半导体纳米材料中，ZnO因激子束缚能大（60meV），可在室温获得高效的紫外发光而成为近年来继GaN材料后的又一研究热点．外延生长一维纳米结构ZnO及其量子阱材料除因量子尺寸效应更适宜做室温紫外发光、激光材料与器件外，还因界面和量子限制效应而具有许多新奇的光、电、和力学特性，可应用于纳米光电子学器件，传感器及存储器件，纳米尺度共振隧道结型器件和场效应晶体管的研制和开发．文章着重介绍了目前ZnO一维纳米结构制备，一维ZnO纳米异质结构和一维ZnO／Zn1-xMgxO多量子阱结构的外延生长和研究进展．     

染料掺杂聚合物薄膜中金纳米颗粒增强的随机激光

基于金属纳米结构而获得随机激光的增强,其独特的性质及其潜在的应用价值具有重要的研究意义,在表面增强荧光、光学开关器件、表面等离子激元激光等方面实现了较多应用。报道一种快捷有效的制备纳米颗粒的手段并基于该纳米颗粒结构分析了染料掺杂聚合物薄膜涂覆的随机激光现象和规律。利用离子溅射沉积和高温热处理在石英基底上制备了Au纳米颗粒,改变溅射时间Au纳米颗粒的尺寸发生可控变化,该方法便捷、工艺简单。研究采用40,80和120 s三种不同的时间进行Au膜溅射并在650 ℃下高温处理,得到粒径尺寸不同的Au纳米颗粒,随着溅射时间延长Au纳米颗粒的尺寸逐渐变大。通过涂覆有机荧光染料DCJTB掺杂的PMMA聚合物薄膜构建光致激射系统,利用纳秒脉冲激光对样品进行激发,得到随机激光并研究其出射光强度和阈值的变化规律特征。40,80和120 s三种溅射时间下所得Au纳米颗粒的平均粒径尺寸分别为230,250和390 nm,在532 nm激光激发下产生随机激光的阈值分别为20.5,17.5和12.5 μJ·pulse-1。Au纳米颗粒尺寸越大、粒子间距越小时,光子散射的平均自由程越短,光在金属颗粒之间可以多次有效散射,从而显著提高散射效率,产生较低阈值的激光发射;Au纳米颗粒的吸收峰与染料的荧光峰恰好匹配时,将会显著增强染料的荧光效应,激发更多染料分子发生能级跃迁,增加光子态密度,获得峰值更高、阈值更低的激射现象;泵浦光不破坏染料分子的情况下,可以多次循环泵浦获得激光,染料分子的发光效率随着多次激发略有降低,有助于随机激光器件的研究开发。实验研究结果与理论分析相一致,进一步明确了Au纳米颗粒对光子散射和等离子共振对光吸收增强的随机激光发射机理。该研究以Au纳米结构对光子的强散射效应为增益,通过理论分析和实验测量获得随机激光,为实现高效率、低阈值的随机激光研究提供了一种便捷的技术手段,有望促进随机激光器件的开发和应用。     

MZ-MMI-based all-optical switch using nonlinear coupled waveguides

We propose an all-optical switch (AOS) based on Mach-Zehnder (MZ) and Multi-mode interference (MMI) using nonlinear closely coupled waveguides. The device operates by switching between two states of coupled waveguides. In first state the refractive index of waveguides are same and light field will completely couple to nonlinear waveguide in half length of coupler and will back in the second half. We will have π phase difference in this procedure and the input field will appear in Bar-state output. In the second state the refractive index of nonlinear waveguide increase with high intensity control field. In this case, we have lower coupling and change in phase. But, we choose the best refractive index change to obtain the phase change of multiple of 2π necessary for Cross-state in output. The beam propagation method is used to simulate the device operation.     

All-optical logic gates with bacteriorhodopsin

All-optical logic gates with bacteriorhodopsin (bR) protein molecules have been demonstrated based on all-optical switching of a cw probe laser beam by multiple pulsed pump laser beams due to nonlinear intensity-induced excited-state absorption. A cw probe laser beam at 640 nm corresponding to the peak absorption of O-state in the bR photocycle is switched by a pulsed pump laser beam at 570 nm corresponding to the maximum initial B state absorption, at relatively low powers. The switching characteristics have been used to design all-optical NOT and the universal NOR and NAND logic gates and the effect of various parameters such as variation in pump pulse width, pump intensity, lifetime of O state and absorption cross-section of the B state at probe wavelength on the switching characteristics has been analyzed.     

All-optical polarization switching based on Bragg-spaced quantum dots layers

One kind of Bragg-spaced all-optical switching has been proposed in this paper, and the quantum dots ensembles are used in it as active layers. By one-dimensional photonic crystal theory and transmission matrix method, we have studied the reflectivity stop band and switching effect based on the ac Stark effect. The reflectivity stop band of this switch can be suppressed or recovered, and the circular dichroism and birefringence are induced by a circle-polarized control light, which result in a significant polarization switching effect. This switching structure shows great advantages of lower requirement of pump light intensity, larger contrast ratio than that of Bragg-spaced quantum wells with the same period, especially this switching can be used at room temperature theoretically. So we predict that there are prodigious prospects for its using in high speed optical communications as all-optical switching.     

All-optical switching effect based on azodye-doped polymer thin films

A simple all-optical switch based on photoinduced birefringence effect is demonstrated in azo dye (DR1) doped polymer (PMMA) thin films. The all-optical switching effect has been studied at different control beam power and different temperatures of the sample. With a control power of 30.7 mW and at 56 ℃, the response time of the switching is less than 5 ms, and the depth of the modulation reaches 80%.     

Optical Switching in Silicon Nanowaveguide Ring Resonators Based on Kerr Effect and TPA Effect

We analyze theoretically the 1 × 2 low-power all-optical switching in silicon nanowaveguide ring resonators （RR） based on the Kerr effect and two-photon absorption （TPA）, and give a comparison between both the all-optical switches. The calculation shows that the switching power of the TPA-RR switch is 3 orders smaller than that of the Kerr-RR switch. The switching time for both the switches is about 100ps.     

An all-optical comparison scheme between two multi-bit data with optical nonlinear material

Over the last few decades, several all-optical circuits have been proposed to meet the need of high-speed data processing. In some information processing architectures, the role of various analog and digital data comparisons is very important. In this letter, we proposed a multi-bit data comparison scheme. The scheme is based on the switching property of optical nonlinear material. Ultrafast operational speed larger than gigahertz can be expected from this all-optical scheme.OCIS codes: 190.0190, 200.0200, 200.1130, 200.3760.     

光纤激光器的偏振开关操作

本文阐述了采用光子注入法实现光纤激光器的偏振开关操作.这种新颖的全光开关器件具有极低的阈值(0.1μW).对操作机理、实验实现和器件特性.     

Au/MXene based ultrafast all-optical switching

All-optical switches have arisen great attention due to their ultrafast speed as compared with electric switches. However, the excellent optical properties and strong interaction of two-dimensional (2D) material MXene show great potentials in next-generation all-optical switching. As a solution, we propose all-optical switching used Au/MXene with switching full width at half maximum (FWHM) operating at 290 fs. Compared with pure MXene, the Au/MXene behaves outstanding performances due to local surface plasmon resonance (LSPR), including broadband differential transmission, strong near-infrared on/off ratio enhancement. Remarkably, this study enhances understanding of Au/MXene based ultrafast all-optical switching red-shifted about 34 nm in comparison to MXene, validating all optical properties of Au/MXene opening the way to the implementation of optical interconnection and optical switching.     

Designing of an all-optical scheme for single input ternary logical operations

In this paper, for the first time to our knowledge, we propose and describe a novel design of single circuit capable of generating all the possible 27 logic functions for single input ternary (3-valued) logic system in all-optical domain. Here the different logical states have been represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch plays a significant role as ultra-fast all-optical switching device. Proposed all-optical circuit is numerically investigated and simulated.