Effective Nonlinear Response of the Nonlinear Random Mixed Composites

A simple self-consistent mean-field theory is used to study the nonlinear composites consisting of linear and strongly nonlinear materials or strongly nonlinear materials with different nonlinear exponents. The effective nonlinear response obtained is compared with simulation data. Good agreement is found. Meanwhile, we study the effect of granular shapes (depolarization factor g) in different external applied fields on the nonlinear response of nonlinear random composites. It is found that the factor g affects the effective nonlinear response greatly in certain conditions.     

具有几个光振荡周期的飞秒激光脉冲

从麦克斯韦方程组出发 ,推导出了具有几个光振荡周期的飞秒激光脉冲在非线性光纤中传输的方程和非线性光纤的折射率。给出了描述具有几个光振荡周期的飞秒激光脉冲在非线性光纤中传输方程的解。研究了在非线性光纤中自相位调制导致具有几个光振荡周期的飞秒激光脉冲频谱展宽 (脉宽压缩 )的详细物理过程。研究了非线性光纤中飞秒光孤子产生的条件     

飞秒激光在PPQ有机高聚物中的传输特性研究

有机高聚物是一种具有大非线性系数和较快非线性响应时间的非线性材料。本文通过对含有二阶，三阶色散效应和非线性响应时间改进的非线性薛定谔方程进行了数值模拟求解，分析了飞秒光脉冲在有机高聚物聚苯基喹恶啉中的传输特性。     

组件非线性响应人工神经网络建模及在传导干扰分析中的应用

根据描述大信号激励下组件响应的黑箱模型——非线性散射参数,提出利用有限实验数据通过人工神经网络建模获得组件非线性散射参数的方法,利用该方法对二极管构成的非线性组件的预测结果与实验测量结果吻合良好。推导了二端口非线性器件与三端口线性器件的非线性散射参数级联计算公式,并讨论非线性散射参数在传导干扰分析中的应用。通过具体实例的计算结果与实测结果的对比,证明了基于人工神经网络学习模型的非线性散射参数获取方法非常便于包含非线性组件的传导干扰分析,这对于系统级电磁效应分析具有重要意义。     

Interaction dynamics of elastic waves with a complex nonlinear scatterer through the use of a time reversal mirror

This Letter reports on work performed to locate and interrogate a nonlinear scatterer in a linearly elastic medium through the use of a time reversal mirror in combination with nonlinear dynamics. Time reversal provides the means to spatially and temporally localize elastic energy on a scattering feature while the nonlinear dynamics spectrum allows one to determine whether the scatterer is nonlinear (e.g., mechanical damage). Here elastic waves are measured in a solid and processed to extract the nonlinear elastic response. The processed elastic signals are then time reversed, rebroadcast, and found to focus on the nonlinear scatterer, thus defining a time-reversed nonlinear elastic wave spectroscopy process. Additionally, the focusing process illuminates the complexity of the nonlinear scatterer in both space and time, providing a means to image and investigate the origins and physical mechanisms of the nonlinear elastic response.     

Nonlinear Squeezed States and Multiplication Rule of Nonlinear Squeezing Operators Gained via Nonlinear Coherent State Representation and IWOP Technique

Using the nonlinear coherent state representation we derive nonlinear squeezed states and the multiplication rule of nonlinear squeezing operators. We find that the symplectic matrices multiplication rule in nonlinear coherent state projection operator representation maps into the multiplication rule of successive nonlinear squeezing operators.The technique of integral within an ordered product of operators plays an essential role in deriving the multiplication rule.     

非线性多端网络理论

作为对非线性网络研究上的一个尝试,在文中引入了多端网络理论,研究限于具有恒定通量的非线性网络。得到了关于非线性N端,2n端,p+1端,2(p+1)端网络的两个基本性质。     

The study of the nonlinear absorption in the nonlinear-imaging technique with phase object

The nonlinear absorption can produce a nonlinear image very similar with the one created by the nonlinear refraction when using the nonlinear-imaging technique with phase object to measure the third-order nonlinearity of materials, but the principles of them are different. The formation of the nonlinear absorption image is explained, and the condition that the highest sensitivity of the nonlinear absorption measurement can be reached is deduced. For the materials with both nonlinear absorption and refraction, we find a proper phase shift of the phase object where the effect of the nonlinear refraction to the measured signal can be eliminated. The nonlinear absorption and refraction are numerically simulated when the phase shift of phase object to be π/2 that is normally used. The qualitative tendency of the signal variation is presented.     

圆杆波导中的一个非线性波动方程及准确周期解

在小变形条件下，采用Cox的非线性应力应变关系，计及横向Possion效应，借助Hamilton变分原理导出了非线性弹性圆杆波导中的纵向波动方程. 利用Jacobi椭圆余弦函数展开法，对该方程与截断的非线性波动方程进行求解，得到了两类非线性波动方程的准确周期解，它们可以进一步退化为孤波解. 关键词： 非线性波 Possion效应 Jacobi椭圆余弦函数     

一类弹性和阻尼双分段非线性约束系统周期响应特性研究

考虑动态条件下的两种典型分段非线性约束, 根据广义耗散Lagrange原理建立一类具有弹性和阻尼双分段非线性约束系统动力学模型. 采用平均法求解得到系统在周期激励下的幅频响应关系. 分别比较系统在不同分段非线性约束条件下的时域响应、分岔响应和幅频响应, 得到受分段非线性约束的系统响应特性以及约束条件变化时系统响应的变化规律. 对比两种约束条件下的幅频响应, 研究得到系统稳定性受不同分段非线性因素影响及两种分段非线性约束之间的相互影响规律.     

非线性频率转换新原理新平台与新应用研究

作为最早发现的非线性光学现象之一,非线性频率转换经过几十年的发展,从原理到应用均已不断成熟。非线性频率转换过程中新的相位匹配原理被不断提出和实现。除此之外,随着集成光学、结构光子学及量子光学等领域的不断发展,非线性频率转换在各领域的研究和应用又重新焕发活力,并发挥着不可替代的作用。本篇综述围绕非线性频率转换主题,突出非线性频率转换的新原理、新平台与新应用研究,并以本团队研究成果为基础,介绍相关领域的研究进展,主要分为以下几个方面:非线性界面相位匹配新原理;结构光场非线性谐波调控;铌酸锂薄膜集成非线性光学新平台;单光子频率转换、光量子接口等新应用。     

振动声调制技术下微裂纹的非线性响应分析

采用非线性弹簧模型对振动声调制技术下微裂纹产生的非线性调制效应进行解释。从理论上分析了振动声调制技术下微裂纹产生非线性调制现象的原理,将微裂纹的开合状态等效为非线性弹簧。利用有限元软件构建并仿真微裂纹非线性弹簧模型,分别观察不同激励下裂纹界面的开合状态及混合声波的传播特性。结果表明,微裂纹界面随低频声波呈周期性开合,使得通过裂纹界面的高频声波与低频声波相互调制而产生非线性现象。在以上研究基础上,开展振动声调制实验研究。对比仿真结果,非线性调制系数R在实验条件下和仿真随低频激励幅值的变化趋势相同,证明了该模型的正确性。该模型为振动声调制技术应用于微裂纹的超声非线性检测提供了理论依据。      

Nonlinear Squeezed States and Multiplication Rule of Nonlinear Squeezing Operators Gained via Nonlinear Coherent State Representation and IWOP Technique

Using the nonlinear coherent state representation we derive nonlinear squeezed states and the multiplication rule of nonlinear squeezing operators. We find that the symplectic matrices multiplication rule in nonlinear coherent state projection operator representation maps into the multiplication rule of successive nonlinear squeezing operators.The technique of integral within an ordered product of operators plays an essential role in deriving the multiplication rule.     

Investigation of optical nonlinearities in Pd(po)2 by Z-scan technique

With nanosecond scale at a 532 nm wavelength, we firstly measured the nonlinear optical absorption and refraction coefficients of Pd(po)₂ complex by using Z-scan technique, here Hpo=1-hydioxy-2-pyridone. We describe an empirical expression for the case when nonlinear refraction is accompanied by nonlinear absorption to separately evaluate the nonlinear refraction and the nonlinear absorption by performing straightforward measurements with the aperture removed. The nonlinear optical response of Pd(po)₂ was determined by the linear decreasing irradiance-dependence. The nonlinear absorption originates from the near resonant two-photon absorption while the mechanism of the nonlinear refraction is the near resonant two-photon absorption transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant two-photon absorption.     

Third-Order Nonlinear Optical Susceptibility of Indium Phosphide Nanocrystals

InP nanocrystals synthesized by refluxing and annealing of organic solvent are determined from XRD measurements to have an averse granularity of 25 nm. The nonlinear optical properties of the InP nanocrystals studied by using laser Z-scan technique with 50 ps pulses at 532nm are found to reveal strong nonlinear optical properties and two-photon absorption phenomenon. Also, the nonlinear absorption coeffcient, the nonlinear refractive index and the third-order nonlinear optical susceptibility are determined by experiments, in which the nonlinear refractive index is three orders of magnitude larger than that of bulk InP.     

Two-dimensional nonlinear beam shaping

We develop a technique for two-dimensional arbitrary wavefront shaping in quadratic nonlinear crystals by using binary nonlinear computer generated holograms. The method is based on transverse illumination of a binary modulated nonlinear photonic crystal, where the phase matching is partially satisfied through the nonlinear Raman-Nath process. We demonstrate the method experimentally showing a conversion of a fundamental Gaussian beam pump light into three Hermite-Gaussian and three Laguerre-Gaussian beams in the second harmonic. Two-dimensional binary nonlinear computer generated holograms open wide possibilities in the field of nonlinear beam shaping and mode conversion.     

Nonlinear refraction and nonlinear absorption of silver aggregates in a polymeric matrix

The nonlinear optical characteristics of silver aggregates in a polymeric matrix are studied by the Z-scan method at the wavelength λ = 1064 nm. The nonlinear refractive index and the third-order nonlinear susceptibility of a sample with silver aggregates are measured. It is shown that the nonlinear refraction in the sample is related to the Kerr effect. The character of the nonlinear absorption process is discussed.     

Z-scan measurement of the nonlinear refractive index of graphene

Under strong laser illumination, few-layer graphene exhibits both a transmittance increase due to saturable absorption and a nonlinear phase shift. Here, we unambiguously distinguish these two nonlinear optical effects and identify both real and imaginary parts of the complex nonlinear refractive index of graphene. We show that graphene possesses a giant nonlinear refractive index n(2)?10(-7) cm(2) W(-1), almost 9 orders of magnitude larger than bulk dielectrics. We find that the nonlinear refractive index decreases with increasing excitation flux but slower than the absorption. This suggests that graphene may be a very promising nonlinear medium, paving the way for graphene-based nonlinear photonics.     

Subwavelength discrete solitons in nonlinear metamaterials

We present the first study of subwavelength discrete solitons in nonlinear metamaterials: nanoscaled periodic structures consisting of metal and nonlinear dielectric slabs. The solitons supported by such media result from a balance between tunneling of surface plasmon modes and nonlinear self-trapping. The dynamics in such systems, arising from the threefold interplay between periodicity, nonlinearity, and surface plasmon polaritons, is substantially different from that in conventional nonlinear dielectric waveguide arrays. We expect these phenomena to inspire fundamental studies as well as potential applications of nonlinear metamaterials, particularly in subwavelength nonlinear optics.     

The modified propagation equation for TM polarized subwavelength spatial solitons in a nonlinear planar waveguide

The wave equation of TM polarized subwavelength beam propagations in a nonlinear planar waveguide is derived beyond the paraxial approximation. This modified equation contains more higher-order linear and nonlinear terms than the nonlinear Schrödinger equation. The propagation of fundamental subwavelength spatial solitons is numerically studied. It is shown that the effect of the higher nonlinear terms is significant. That is, for the propagation of narrower beam the modified nonlinear Schrödinger equation is more suitable than the nonlinear Schrödinger equation.