非线性光学五十年

文章简要回顾了非线性光学的诞生以及早期的发展,包括二次谐波,激光和频和差频现象,受激拉曼散射,以及激光的一些自作用行为等,介绍了非线性光学的一些重要研究成果和应用,包括非线性光谱学,位相共轭和自适应光学,相干非线性光学以及高次谐波等,最后对非线性光学当前和未来研究热点作了总结和展望.     

HMO in geometrical optics

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Kramers-Kronig type of dispersion relation in nonlinear optics

The applicability of Kramers-Kronig (K-K) relation under nearly sharp resonant transition regime in narrow-gap semiconductors has been established and consequently, a generalized dispersion relation for nonlinear optical susceptibility of a dielectric is derived. This relation can be employed in the study of nonlinear optical processes in solids as well as in plasmas over a wide frequency spectrum.     

Self-trapping and Self-focusing of Light Beams in Uniaxial Crystals

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高斯光束非线性“热像”效应研究

高功率激光系统中非线性“热像”强度可能达到光学元件损伤阀值，从而对系统的安全运行造成威胁.以往的非线性“热像”现象研究都是基于无限大平面光波背景，但实际系统中传输的是有限束宽光束.本文以高斯光束为例，基于无像差自聚焦理论分析了有限束宽光束的“热像”形成规律.结果表明，高斯光束“热像”的强度与位置在光束腰斑较小时与平面光波情况有明显不同，但光束腰斑较衍射物大得多时，高斯光束可以近似当作平面光波处理.     

HMO model of scalar field in medium and self-focusing

In this paper, the HMO model of scalar field in medium is presented using the general covariant classical theory of scalar field in medium, which is regarded as a curved space-time represented by optical metric model (OMM) and the case of self-focusing is discussed.     

Dynamics of resonant self-focusing on second harmonic generation of Gaussian laser beam in a rippled density plasma

Resonant second harmonic generation by a Gaussian laser beam in a rippled density plasma is studied using the moment theory approach. The nonlinearity arises through the relativistic mass effect and ponderomotive forces. The laser beam creates a plasma channel and gives rise to electron density perturbation at the laser frequency. The density perturbation beats with electron quiver velocity to produce second harmonics. The ripple provides phase matching and makes the process a resonant one. The second harmonic power efficiency is increased effectively with density ripple. Self-focusing causes enhancement in the efficiency of harmonic generation.     

基于光线光学的非线性自聚焦现象的仿真分析

采用光线光学方法对非线性自聚焦现象进行仿真, 能够从宏观上直观地体现强激光的传输过程, 同时避免采用近轴近似、自相似近似等. 本文采用在光传输路径上垂直于光轴切片的方法, 将光的非线性传输转化为切片上的光对折射率的调制作用和切片间的线性传输. 在切片端面上统计光强后对量化误差进行了抑制, 而线性传输过程采用了亚当斯法求解光线方程从而解决了龙格库塔法等不能用于非线性光传输仿真的问题. 仿真结果显示, 强激光自聚焦在轴上有多个焦点, 且第一个焦点的位置随光功率的增大而更靠近入射位置; 由于追迹的是实际光线, 故可以得到近轴区以外区域自聚焦及成丝(环)的情况, 这对于强激光系统安全是有重要意义的. 利用已有的同样基于光线追迹方法的光学设计、仿真软件, 可以把非线性自聚焦介质和线性介质结合起来, 仿真光在实际强激光系统中的传输. 关键词： 实际光线追迹 非线性自聚焦 光传输仿真     

Kagome光纤超快非线性光学研究进展

Kagome光纤(简称KGF)是一种不依赖带隙导光的新型空芯微结构光纤,其结构设计灵活、损伤阈值高、损耗低(高透区损耗可低至~40 dB/km)、支持宽带传输(&;amp;lt;500 nm),并可通过纤芯改变所充气体及调节气压实现光纤色散、非线性效应的有效调制,在强场物理、超快激光技术等领域研究中优势突出。基于KGF在超快光学中的重要意义,该文对近年来国际上关于KGF在非线性光学变频及超短脉冲压缩等领域的研究成果进行介绍,并对关键性应用技术进行简要分析,最后对其发展前景进行展望。     

手性分子介质非线性光学研究新进展

文章介绍了近年来手性分子介质及材料的非线性光学性质的研究状况，综述了手性分子非线性微观模型的使用情况，给出了一些典型的二阶、三阶非线性光学实验结果，用这些微观模型可以正确地分析这些结果．同时指出了未来研究的趋势，及研究成果可能应用的领域．     

飞秒非线性光学的最新进展——几个周期超短超强激光脉冲的非线性光学

 本文介绍了飞秒非线性光脉冲研究的最新进展。超快技术的发展已经能够产生仅含几个振荡周期的超强脉冲,其强度梯度使电子可以存在于比库仑束缚场高许多倍的外场产生的原子束缚态,并产生了同光频相差不大的电离率,从而导致了非线性光学的一些新的特点。     

飞秒非线性光学的最新进展——几个周期超短超强激光脉冲的非线性光学

本文介绍了飞秒非线性光脉冲研究的最新进展。超快技术的发展已经能够产生仅含几个振荡周期的超强脉冲,其强度梯度使电子可以存在于比库仑束缚场高许多倍的外场产生的原子束缚态,并产生了同光频相差不大的电离率,从而导致了非线性光学的一些新的特点。     

Modelling of strongly nonlinear sinusoidal Bragg gratings by the Method of Single Expression

The one-dimensional problem of plane EM wave interaction with strongly nonlinear sinusoidal Bragg gratings is exactly solved using the new Method of Single Expression (MSE). The basic point of the method is the presentation of the electrical field in the modulated medium (Bragg grating) in the form of a single expression, contrary to the traditional counter-propagating waves approach. The spectral characteristics of linear Bragg gratings of different length are presented. The influence of loss or gain on the spectral characteristics of Bragg gratings is considered. The electrical field amplitude distributions along a grating at the wavelengths corresponding to the minima and maxima of reflectivity in the vicinity of the Bragg resonance are illustrated. Bistable and multistable dependences of reflectivity on the incident electrical field amplitude are obtained for negative and positive nonlinearities.     

All Optical Light Deflection and Displacement Using Nonlinear Slab Waveguide

The possibility of all optical control of light deflection and displacement through a planar nonlinear waveguide has been discussed in this article. In this scheme a strong command beam controls the propagation characteristics of a weak signal beam in a nonlinear waveguide. Employing variational approach, we have established a set of coupled nonlinear equations for the displacement of the center of gravity, beam size, deflection angle, and beam divergence of the signal beam. These equations have been solved numerically to confirm the possibility of all optical control of deflection and displacement of a signal beam by a command beam.     

非相干非线性光学理论方法及其进展

文章主要综述了非相干非线性光学的几种理论方法,包括互相干函数法、相干密度法、自洽模理论、Wigner转换法、近似射线光学法和热动力学法等.其中,着重阐述了近期发展起来的理论方法——热动力学法,并对其原理进行了概括.对这几种理论方法的理解和探讨对非相干非线性光学效应的研究具有很重要的指导意义,有利于非相干非线性光学理论的进一步发展和完善.     

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.     

A variational approach to nonlinear evolution equations in optics

A tutorial review is presented of the use of direct variational methods based on Rayleigh-Ritz optimization for finding approximate solutions to various nonlinear evolution equations. The practical application of the approach is demonstrated by some illustrative examples in connection with the nonlinear Schrödinger equation.     

非相干非线性光学理论方法及其进展

文章主要综述了非相干非线性光学的几种理论方法,包括互相干函数法、相干密度法、自洽模理论、Wigner转换法、近似射线光学法和热动力学法等.其中,着重阐述了近期发展起来的理论方法——热动力学法,并对其原理进行了概括.对这几种理论方法的理解和探讨对非相干非线性光学效应的研究具有很重要的指导意义,有利于非相干非线性光学理论的进一步发展和完善.     

Dielectric superlattices for nonlinear optical effects

Dielectric superlattices show a lot of new phenomena that are promising in applications, such as nonlinear optical frequency conversion and optical bistability. This paper reviews the main achievements in this field. Much has been focused on the work done in our Lab. Since 1980, we have extended the concept of superlattice from semiconductor to dielectrics. When quasi-phase-matching technique is introduced into a quasiperiodic dielectric superlattice, more interesting phenomena can occur. For example, multiwavelength second-harmonic generation and coupled parametric processes such as direct third-harmonic generation have been realized with high efficiency. A new mechanism for optical bistability in a 2-dimensional dielectric superlattice, i.e. a 2-dimensional nonlinear photonic crystal, has been proposed theoretically had proved experimentally.