光速减慢

激光技术的发展为极限光速的测量提供了有效工具,主要介绍了光束减慢有关的非线性光学知识和光速减慢的实验原理及方法,光束减慢实验中用的低温Na 原子气在探测激光和耦合激光的共同作用下处于量子相干态－－一种非线性要化状态,由于电磁感应透明效应（EIT）,探测光可以使介质的折射率改变并能透过Na原子气,使光速减慢的测量变为现实。     

等效双芯光纤通信中消除孤子分裂与变形的方法

籍助等效双波导孤子耦合模型，利用自伴算符方法，通过高阶色散耦合非线性薛定谔方程，分析了光纤通信中孤子的传输与耦合特性，提出了利用强抽运光在非线性光学介质中诱导出的相位孔来补偿探测光的衍射，从而消除光学孤子分裂与变形的方法．     

激光等离子体冲击波波阵面衰减特性的实验研究

采用光偏转法分别对空气及水中的激光等离子体冲击波信号进行了探测。研究了自由衰减条件下,激光等离子体冲击波波阵面的衰减特性,并讨论了作用激光能量以及介质的物理特性对冲击波波阵面衰减特性的影响。结论表明,采用光偏转法可以有效地探测各种透明流体介质中的激光等离子体冲击波;同种介质中,作用激光能量越大,冲击波衰减越慢;作用激光能量相同,冲击波在波阻抗较小的介质中衰减较慢。     

铯原子A型塞曼子能级结构中的电磁诱导透明

采用左旋和右旋圆偏振光分别作为探测光和耦合光，作用于铯原子6^2S12F=3-6^2P32F’=2简并二能级系统，借助探测光的吸收光谱观察到了由简并二能级中A型塞曼子能级结构导致的电磁诱导透明(EIT)现象。同时研究了不同耦合光的强度和失谐对电磁诱导透明的影响。由于在多普勒展宽背景下圆偏振光对塞曼子能级间的光抽运，从而不同塞曼子能级上布居出现明显的差异，电磁诱导透明的作用程度有所不同。而且对于在扫描探测光频率时由于存在速度选择机制使探测光通过铯气室后的吸收谱线发生的畸变作了定性分析。     

吸收介质中三阶极化率的测量

全光学信息处理、光计算机的发展依赖于具有大的三阶非线性光学材料,因此介质的三阶非线性极化率的测量就显得特别重要。吴存恺等提出了用简并四波混频方法测量透明介质的三阶极化率,G.R.Olbright用于涉法测量了CdS_xSe(1-x)玻璃的非线性折射率。本文将讨论用简并四波混频测量吸收介质的三阶极化率的方法。     

热透镜显像现象研究

本文报导了弱探测光在热透镜介质中传播时出现的一种光感应现象，实验研究了探测光出射光斑中的暗斑与介质中热透镜的对应关系，并分析了该现象产生的机理。     

光纤放大器中原子介质的折射率变化

本文用三能级原子模型描述双频场中光纤放大器的原子介质，讨论介质对弱探测场透明以及折射率变化。     

铯原子∧型塞曼子能级结构中的电磁诱导透明

采用左旋和右旋圆偏振光分别作为探测光和耦合光,作用于铯原子62S1/2F=3-62P3/2F′=2简并二能级系统,借助探测光的吸收光谱观察到了由简并二能级中A型塞曼子能级结构导致的电磁诱导透明(EIT)现象.同时研究了不同耦合光的强度和失谐对电磁诱导透明的影响.由于在多普勒展宽背景下圆偏振光对塞曼子能级间的光抽运,从而不同塞曼子能级上布居出现明显的差异,电磁诱导透明的作用程度有所不同.而且对于在扫描探测光频率时由于存在速度选择机制使探测光通过铯气室后的吸收谱线发生的畸变作了定性分析.     

热透镜显像现象研究

本文报导了弱探测光在热透镜介质中传播时出现的一种光感应现象。实验研究了探测光出射光斑中的暗斑与介质中热透镜的对应关系，并分析了该现象产生的机理。     

不对称双量子点系统中电压调控Kerr非线性增强

从理论上研究了不对称双量子点系统内的Kerr非线性增强效应。系统内量子点间的电压隧穿效应,可以在两个不同的探测频率位置同时诱导电磁感应透明。调节隧穿电压及控制光场可以改变吸收性质,从而得到其中一个透明窗口内无线性和非线性吸收的Kerr非线性增强效应。分析表明,量子点间的电压调控引起的隧穿是产生Kerr非线性增强的关键因素。     

Complex-Point Dipole Formulation of Probe-Corrected Cylindrical and Spherical Near-Field Scanning of Electromagnetic Fields

A probe-corrected electromagnetic theory based on complex-point dipoles is presented for computing the field of an arbitrary source of finite extent (for example a test antenna) from measurements of its near field on a cylindrical or spherical scanning surface. By representing the probe with complex-point dipoles, probe correction is achieved by simple factors that involve Hankel functions evaluated at complex points. Only four complex-point dipoles are needed to represent a typical precision probe used in near-field measurements. The theory uses neither translation and rotation theorems nor differential operators. One disadvantage of the theory is that it employs nonlinear optimization to determine the parameters of the probe model. The complex-point dipole representation of the probe makes realistic simulations of near-field scanning systems straightforward. The cylindrical theory is validated through a numerical example. The spherical theory is validated by experimental data.     

Numerical analysis technique for diode-loaded dipole antennas

A circuit model for a double-loaded dipole electric field measurement probe that is valid for frequencies below 10 GHz is developed. A nonnegligible dipole radius and the nonlinear characteristics of the diode are taken into consideration. The dipole lumped-circuit elements and diode capacitances are determined by theoretical means, while the diode V-I characteristics and resistance are determined by a combined theoretical and empirical approach. Newton's iteration method is used to numerically solve the resulting nonlinear differential equation. Experimental measurements on a probe designed for operation between 1 and 1000 MHz are reported and compared with the theoretical results     

A nonstationary probe that is self-consistently negatively charged and embedded in plasma

The dynamics of ions in a plasma layer adjacent to the conducting surface of an electrically insulated negatively charged probe is studied. Exact self-consistent analytical solutions to the nonlinear system of equations of ion hydrodynamics are obtained. The solutions satisfy nonstationary boundary conditions on the probe’s surface. The intensity of the electric field and the velocity, concentration, and density of the ion current are found as functions of the initial position of a particle and the distance to the probe’s surface. The rate of change in the probe’s charge is determined and it is shown that, with time, the parameters of the system considered approach their asymptotical values. For a spherical probe, the time dependence of the ion-current density, i.e., the probe’s transient response (which is an analogue of the current—voltage characteristic of the Langmuir probe with a constant negative bias), is obtained.     

Nearly degenerate four-wave mixing in distributed feedbacksemiconductor lasers operating above threshold

Nearly degenerate four-wave mixing in distributed feedback semiconductor lasers above threshold in investigated theoretically and experimentally. The experimental results reveal an almost symmetric amplification of probe and conjugate fields versus frequency with respect to zero pump-probe detuning, in contrast with observations in traveling wave amplifiers. The result of the theory, based on the coupled mode formalism, is a set of nonlinear differential equations which are solved in the mean field approximation. The theory is shown to match well with the experimental results when the effect of the nonlinear gain compression is taken into account     

Nanoscale Origins of Nonlinear Behavior in Ferroic Thin Films

The nonlinear response of a ferroic to an applied field has been studied through the phenomenological Rayleigh Law for over a hundred years. Yet, despite this, the fundamental physical mechanisms at the nanoscale that lead to macroscopic Rayleigh behavior have remained largely elusive, and experimental evidence at small length scales is limited. Here, it is shown using a combination of scanning probe techniques and phase field modeling, that nanoscale piezoelectric response in prototypical Pb(Zr,Ti)O₃ films appears to follow a distinctly non‐Rayleigh regime. Through statistical analysis, it is found that an averaging of local responses can lead directly to Rayleigh‐like behavior of the strain on a macroscale. Phase‐field modeling confirms the twist of the ferroelastic interface is key in enhancing piezoelectric response. The studies shed light on the nanoscale origins of nonlinear behavior in disordered ferroics.     

Vector theory of cross-phase modulation: role of nonlinear polarization rotation

We develop a vector theory of cross-phase modulation (XPM) capable of describing nonlinear coupling between two pulses of different wavelengths and arbitrary states of polarization. We focus for simplicity on the pump-probe configuration and use it to investigate the temporal and spectral polarization effects occurring inside an optical fiber. Using the Stokes-vector formalism we show that the probe polarization changes in general through XPM-induced nonlinear polarization rotation. In the absence of dispersion-induced probe broadening, such nonlinear changes in the probe polarization do not affect the temporal shape of the probe pulse but produce a multipeak spectrum whose different spectral peaks have different states of polarization. When dispersive effects are included, even the shape of the probe pulse becomes polarization dependent, and different parts of the pulse develop different states of polarization. Such nonlinear polarization effects lead to novel phenomena such as polarization-dependent compression and splitting of the probe pulse.     

Terahertz Wave Gas Photonics: Sensing with Gases

A review of the detection of pulsed terahertz waves via field-induced second harmonic generation in gaseous media is presented. The effects of the DC bias field strength, probe pulse energy, nonlinear susceptibility of the gases, gas pressure, and focusing conditions of the terahertz and optical beams are discussed. A Figure-of-merit, which characterizes the sensitivity of gases media, is introduced.     

Bistability and hysteresis in phase-conjugated reflectivity

An externally driven nonlinear Fabry-Perot interferometer with bistable transmission characteristics is probed through a weak optical field. The nonlinear interaction among the counterpropagating pump beams and the probe beam generates the phase-conjugated beam through intracavity degenerate four-wave mixing. It is shown that the phase-conjugated reflectivity displays bistability and that hysteresis as the driving field is varied in a continuous manner. The analysis is carried out in the mean-field approximation and is valid for the case of low absorption and a high-Qcavity. Both the dispersive and the absorptive effects arising due to saturation of the one-photon resonance are included, and their effect on the phase-conjugated reflectivity is discussed. The results show that, when a bistable device switches on, the reflectivity decreases by a few orders of magnitude. We discuss possible applications and suggest materials where the proposed effects can be seen.     

光纤传输表面电流探头的设计与校准

本文介绍了一种在强电磁场环境中用于检测表面电流强度的光纤传输表面电流探头。采用光纤代替传统的电缆传输,对强电磁场有很好的抗干扰作用,同时也大大减少了对周围空间场的扰乱。其核心的信号处理环节采用直接强度调制式光纤通信,即采用射频晶体管做前级放大,将电压信号转换为电流信号,对光电器件进行直接光强调制。该系统动态范同大,非线性失真小,带宽达到5～120MHz,最大可测试电流为4A。文中给出了光纤传输表面电流探头的校准测试实例以及传输阻抗曲线。     

Optical gating performance using a semiconductor-doped glass etalon

Optical gating is demonstrated using fast-response CdSeTe-doped glass. Continuous-wave probe light and pulsed gate light collinearly illuminate a Fabry-Perot nonlinear optical cavity consisting of two external mirrors and the doped glass. The output of the probe light is gated by the gate light with fast response time. The gating is caused by refractive-index change in the glass due to the carriers generated by the gate light. The nonlinear refractive index of the material is evaluated precisely