基于弱值放大的高精度温度变化测量研究

精确测量温度的变化在现代科技中有重要的意义.极其微小的温度变化通常难以直接测量.依据波片的温度变化引起o光和e光之间相位差改变这一原理,文章搭建了基于偏振的弱值放大系统,将这一温度变化引起的微小的相位差变化量加以放大,并转换为易于测量的光功率的变化量,从而间接测量出多级石英波片的温度变化量,测量精度达到了 0.0042...     

光纤弱值放大中的振幅型噪声和一种抑制方法

弱值放大(WVA)技术可以实现高灵敏度和高精度的光学测量,已经在自由空间平台上得到实验验证。而自由空间平台存在部分光学器件集成化较难、平台稳定性稍弱等问题。要将WVA技术推广到实际应用中,可以利用具有成本更低、规模更小、稳定性更高这些优点的光纤平台。但是,与自由空间平台相比,光纤中的双折射现象更强,足以引起偏振串扰,因此必须考虑振幅型噪声在光纤平台方案中的影响。本文从理论上分析,表明了振幅型噪声会在探测光谱上形成噪声波纹,并损害WVA的灵敏度性能。为了克服这个问题,本文提出了一种后处理方法,仿真的结果表明处理方法的有效性、基于光纤实现WVA的可行性,这为将来设计具有更高灵敏度和稳定性的光学传感器提供了一种可能的方式。     

弱相干场耦合腔系统中的纠缠特性

研究由三个全同的二能级原子与耦合腔构成的系统, 考虑腔场处于弱相干态的情况. 采用Negativity熵度量两子系统间的纠缠, 利用数值计算方法研究了两个原子之间和两个腔场之间的纠缠性质. 讨论了腔场间的耦合系数和腔场的强度对纠缠特性的影响. 研究结果表明: 随光场强度增大, 原子间纠缠和腔场间纠缠均增强. 另一方面, 随耦合腔的耦合系数增大, 两原子间的纠缠减弱, 腔A和腔B间的纠缠增强; 而腔B和腔C间的纠缠, 以及腔A和腔C间纠缠与腔场间的耦合系数间存在非线性关系.     

非线性简并光学参量放大系统的量子起伏

解析求解了P表象中考虑抽运吃空后的非线性含时简并光学参量放大系统获得压缩光所满足的福克尔-普朗克（Fokker-Planck）方程,并且计算了它在阈值附近及远离阈值的量子起伏。研究表明：若略去与η成正比的项,则通解很自然地过渡到线性近似解。计及与η成正比的项后,该解与Drummond等在阈值附近的微扰展开理论相比,基本相符。但在远离阈值处,微扰展开理论不适用,而该结果在阈值附近以及远离阈值的整个区域均是适用的。当μ→0压缩很小时,起伏趋近于真空起伏;而μ〉〉1,压缩增大时,趋近1／1＋μ线性理论。     

Qutip在量子光学中的应用

在量子光学相关课题研究中,光的量子特性以及光与物质相互作用一直是量子光学研究的重要内容之一,利用传统解析手段探索和研究物理问题的范围正受到越来越多的限制,基于计算机语言编程的数值计算手段就显得愈发重要。对于不熟悉数值计算的科学研究人员,基于Python语言的量子工具箱(Qutip)提供了一个成熟可靠的数值计算工具,使得量子光学相关课题的数值计算问题变得简单快捷。本文主要介绍了Qutip的安装和使用及其在量子拉比模型中的应用。     

布拉格型声光双稳系统对弱信号的放大作用研究

在分岔点附近，通过对描述布拉格（Ｂｒａｇｇ）型声光双稳系统的差分－微分方程进行线性稳定性分析，得到了系统对小信号放大时的共振频率，给出了放大倍数的表达式。然后通过数值计算模拟出系统对小信号的放大过程，结果与理论分析相符     

Quantum Partial Searching Algorithm of a Database with Several Target Items

Choi and Korepin [Quantum Information Processing 6（2007）243] presented a quantum partial search algorithm of a database with several target items which can find a target block quickly when each target block contains the same number of target items. Actually, the number of target items in each target block is arbitrary. Aiming at this case, we give a condition to guarantee performance of the partial search algorithm to be performed and the number of queries to oracle of the algorithm to be minimized. In addition, by further numerical computing we come to the conclusion that the more uniform the distribution of target items, the smaller the number of queries.     

原子与弱相干腔场相互作用系统中的量子特性

考虑腔场处于弱相干态的情况,研究了两个全同的二能级原子与耦合腔相互作用系统中原子的偶极压缩和原子间的纠缠特性。研究结果表明,随耦合腔耦合系数增大,原子的偶极压缩减弱。另一方面,随耦合腔耦合系数增大,原子间的纠缠也减弱,这一结果与耦合腔处于真空态的情况相反。     

宽带光学参变啁啾脉冲放大系统的色散控制

在设计宽带光学参变啁啾脉冲放大系统时,对色散源进行了理论分析和讨论。对光学参变啁啾脉冲放大系统的色散量以及各个过程中的高阶色散对脉冲时域和频域特性的影响进行了计算。结果表明展宽器引入了非常大的色散,放大器中信号光相位变化产生的色散较大,参量晶体本身引入的色散相对较小可以忽略不计。输出脉冲宽度主要受二阶色散影响,而三阶和四阶色散主要影响脉冲的波形和信噪比,对频域影响很小。     

Controlling Chaos in a Semiconductor Laser via Weak Optical Positive Feedback and Modulating Amplitude

Numerical analysis of weak optical positive feedback (OPF) controlling chaos is studied in a semiconductor laser.The physical model of controlling chaos produced via modulating the current of semiconductor laser is presented under the condition of OPF.We find the physical mechanism that the nonlinear gain coefficient and linewidth enhancement factor of the laser are affected by OPF so that the dynamical behaviour of the system can be efficiently controlled.Chaos is controlled into a single-periodic state,a dual-periodic state,a fri-periodic state,a quadr-periodic state,a pentaperiodic state,and the laser emitting powers are increased by OPF in simulations.Lastly,another chaos-control method with modulating the amplitude of the feedback light is presented and numerically simulated to control chaotic laser into multi-periodic states.     

光放大外腔式光纤法布里-珀罗干涉传感系统

提出了一种大幅度提高外腔式法布里珀罗干涉传感器干涉信号强度的方法 ,利用掺铒光纤放大自发辐射产生的光源代替一般宽带光源 ,同时由于掺铒光纤的放大作用可以放大干涉信号 ,将光纤法布里珀罗传感器的信号强度提高了 4个数量级 ,因而利用该方法可获得很强的信号和较高的信噪比。介绍了基于光放大的外腔式法布里珀罗干涉传感系统的结构、测量原理及实验。实验结果表明该传感器的应变精度为± 10 με,可满足实际应用的要求。该传感系统在大幅度提高传感器信号强度的同时并未提高系统的成本 ,因此有着较高的性价比和实用价值。     

A Novel Extrinsic Fiber-Optic Fabry-Perot Strain Sensor System Based on Optical Amplification

A novel extrinsic fiber-optic Fabry-Perot interferometric strain sensor system is demonstrated based on the simultaneous use of the amplified spontaneous emission and optical amplification. The improvement of 3～4 orders of magnitude in signal level can be achieved.     

Mode Amplification in Inhomogeneous QD Semiconductor Optical Amplifiers

We present modelling results investigating the carrier dynamics of an SOA composed of an inhomogeneous array of quantum dots designed to produce broad gain amplification when optically pumped. We use a set of rate equations that describe the QDs inhomogeneity and include an energy dependent occupation factor within each inhomogeneously broadened level and numerically solve them with the propagation equation to investigate the amplification of optical signals in the waveguide. By treating the carrier filling according to the quasi-equilibrium distribution, we are able to investigate the effect of band-filling (BFE) on the gain and refractive index. The linewidth enhancement factor (α) is computed and analysed with respect to optical signal intensity as well as electrical current density.     

High and Stable Conversion Efficiency Obtaining in Single-Stage Multi-Crystal Optical Parametric Chirped Pulse Amplification System

An optical parametric chirped-pulse amplification system is demonstrated to provide 32.9% pump-to-signal conversion efficiency. Special techniques are used to make the signal and pump pulses match with each other in both spectral and temporal domains. The broadband 9.5-mJ pulses are produced at the repetition rate of 1 Hz with the gain of over 1.9×10^8. The output energy fluctuation of 7.8% is achieved for the saturated amplification process against the pump fluctuation of 10%.     

周期分布放大系统的精确解及其相互作用

考虑带有变增益侦耗和频率啁啾的非线性薛定谔方程，利用达布变换求得该方程的N-孤子解，并给出带有变增益钡耗和频率啁啾的一孤子解和二孤子解的精确表达式。特别地，详细讨论了孤子周期分布放大系统的动力学行为。结果表明，带有变增益／损耗和频率啁啾的孤子解可以应用于周期分布放大系统，同时保留了孤子的特性。     

Acquisition Time for Ground-to-Satellite Optical Communication System in Weak Atmospheric Turbulence with Spatial Diversity

Abstract

In this article, various issues involved in a ground-to-satellite optical communication link (i.e., acquisition time, uncertainty area, and channel noise) are discussed. Acquisition time of a free-space optical link is evaluated for coherent (sub-carrier BPSK and QPSK) and non-coherent (OOK and -PPM) modulation schemes over weak turbulent channel with transmit diversity. In the analysis, both uncorrelated and correlated beams are considered. It is seen that an increase in transmit diversity order helps to improve the acquisition time, irrespective of turbulence strength in the atmosphere. At high correlation, a marginal change in acquisition time is observed with the increase in diversity order.     

Allocation Algorithm for Optical OFDM Multimode Fiber Communication System

Abstract

A fast bits allocation algorithm is proposed for adaptively modulated optical orthogonal frequency division multiplexing multimode fiber communication system to decrease the system bit error rate caused by some orthogonal frequency division multiplexing subcarriers being located at the deep nulls in the high-frequency region of multimode fiber. Based on a lookup table scheme, the new algorithm dramatically decreases the computational complexity of the Greedy algorithm. The simulation results show that the new algorithm has the same allocation result as the Greedy algorithm, but the computational complexity is considerably lower. In addition, adaptive bits allocation can effectively reduce the system bit error rate.     

基于互强度傅里叶分析的光刻机成像模拟方法

光刻空间像仿真作为各种计算光刻技术的基础,受到越来越多的重视.提出一种基于互强度傅里叶分析的光刻机投影成像快速模拟方法,从光刻成像互强度传播过程入手,基于傅里叶光学原理对成像要素进行多次空域-频域变换,得到一种快捷的空间像模拟途径.通过与标准解析空间像对比,发现该方法的计算精度可达10-4(最大光强归一化).该方法避免了部分相干成像的Hopkins方程中繁琐的积分运算,操作性强、计算精度高.该方法适用于各种灵活多变的曝光成像条件,具备广阔的工程应用前景.