Interface kink solitons in defocusing saturable nonlinear media

We report on the dynamics of semi-localized nonlinear optical modes supported by an interface separating a uniform defocusing saturable medium and an imprinted semi-infinite photonic lattice. Out-of-phase and in-phase kink solitons composed by dark-soliton-like pedestals and oscillatory tails are found. Two branches of out-of-phase kink solitons exist in shallow lattices. Saturable nonlinearity enhances the pedestal height and renormalized energy flow of kink solitons evidently. While in-phase kink solitons are always unstable, out-of-phase kink solitons will be completely stable provided that lattice depth exceeds a critical value. Furthermore, stable kink solitons in the higher band gaps are also possible. Our results may give a helpful hint for understanding the dynamics of kink solitons with high pedestals in other fields.     

The fluctuating phase error analysis in the digital grating phase-shifting profilometry

The nonlinear response of the experimental system and the saturation of fringe patterns can induce the fluctuating phase error in the projection grating phase-shifting profilometry. Two major factors of the fluctuating phase error are discussed by simulation. The fluctuating phase error caused by the nonlinear response of the system is four times the frequency of the fringe pattern when the conventional four-frame phase extracting algorithm is used. However, such error can be decreased by five-frame algorithm. On the other hand, the fluctuating phase error caused by the fringe saturation is five times the frequency of the fringe pattern by using conventional five-frame phase extracting algorithm. A novel phase recovering algorithm is used to decrease the phase error caused by the saturation. Furthermore, the applicability range of the proposed phase recovering algorithm is analyzed by simulation and experiments with different saturation degree of the fringe pattern and nonlinearity of the measurement system.     

Efficient preparation of a four-photon cluster state with homodyne measurement via cross-Kerr nonlinearity

A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photo...     

Field history dependence of nonlinear dielectric properties of Ba0.6Sr0.4TiO3 ceramics under bias electric field: Polarization behavior of polar nano-regions

Nonlinear dielectric properties of Ba_0.6Sr_0.4TiO₃ ceramics prepared by citrate method were investigated under bias electric field with respect to field history. X-ray diffraction analysis and temperature dependence of the dielectric constant (ε_r) confirmed a macroscopically paraelectric state for the specimen at room temperature. A slim polarization versus electric field (P-E) hysteresis loop of the specimen at room temperature indicated the existence of polar nano-regions (PNRs) superimposed on the paraelectric background. The nonlinear dielectric properties in continuous cycles of bias field sweep displayed a strong sensitivity to the field history. This phenomenon was qualitatively explained in terms of an irreversible polarization evolution of the PNRs under the bias fields. A considerable decline of the tunability with the cycle number suggests an appreciable contribution of the PNRs to the dielectric nonlinearity. The polarization and size of the PNRs were determined by fitting the dielectric constants to a multipolarization mechanism model.     

Second-harmonic pressure generation of a non-diffracting acoustical high-order Bessel vortex beam of fractional type α

Background and motivation

Generalized Bessel vortex beams are regaining interest from the standpoint of acoustic scattering and radiation force theories for applications in particle rotation, mixing and manipulation. Other possible applications may include medical and nondestructive imaging. To manipulate heavy particles in a host medium, a minimum threshold of the incident sound field intensity is required at relatively high wave amplitudes such that nonlinear wave propagation occurs and the generation of harmonics may be detected. Thus, predictions of the harmonics generation become crucial from the standpoint of experimental design, and the present analysis should assist in the development of more complete models related to the (nonlinear) scattering and radiation forces under such circumstances. The purpose of this research is to construct a theoretical model for the second-harmonic pressure generation associated with a category of non-diffracting Bessel vortex beams known as high-order Bessel vortex beams of fractional typeα (HOBVBs-Fα).

Method

The weakly nonlinear wave propagation of a HOBVB-Fα is investigated based on Lighthill’s formalism. Analytical solutions up to the second-order level of approximation are derived and discussed. Closed-form solutions are obtained, which are expressed as a function of first-order quantities available from the classical linear theory. Lateral profiles of the HOBVB-Fα are computed and compared.

Results and conclusion

The results show that the beam’s width reduces and becomes narrower, the side-lobes decrease in magnitude, and the hollow region diameter (or null in magnitude) increases as the order of nonlinearity increases. Furthermore, the nonlinearity of the medium preserves the non-diffracting feature of the beam’s second-harmonic generation within the pre-shock range.     

Estimation of anharmonic parameters, molecular radius, Mr and Beyer's non-linearity parameter, B/A in TBnA series

The thermodynamic parameters like Moelwyn-Hughes parameter (C₁), reduced molar volume (V^~), isochoric temperature coefficient of internal pressure (X), Huggin's parameter (F), Gruneisen parameter (Γ_p), isothermal microscopic Gruneisen parameter, Sharma parameter (S_o), fraction free volume (f) and (A^?) a dimensionless thermal parameter, etc and the Beyer's nonlinearity parameter (B/A) were deduced employing the thermal expansion coefficient derived from density data for the homologues series of compounds terephthalyidene-bis-p-n-alkyl anilines, TBnA with n = 5 to 10,12,14,16 and 18. Further, it is found that the variation of molecular radius, M_r increases with the increase of alkyl chain number, with a core radius of 4.78 Å and the increment for methylene unit is 0.086 Å . The results were discussed with the body of the data available.     

S变换轮廓术中消除条纹非线性影响的方法

S变换是短时傅里叶变换和小波变换的延伸和推广,是一种无损可逆的非平稳信号时频分析方法.它不仅具有线性、多分辨性和逆变换唯一性等特点,而且其反变换与傅里叶变换保持着直接的联系.在S变换中,以简谐波作为基波,以可以同时进行伸缩和平移的高斯函数作为窗函数.同短时傅里叶变换相比,S变换的时频分辨率可以同时达到最佳,同小波变换相...     

结构光测量相位波动误差补偿方法研究

在计算机仿真分析投影仪伽马非线性特性对包裹相位波动误差影响的基础上,提出一种面向相移结构光测量的相位波动误差补偿方法.该方法采用二次多项式最小二乘拟合的方法近似输出条纹光强分布,实现包裹相位波动误差的补偿,减小投影仪非线性导致的系统测量误差.此方法简单,运算量小,不依赖环境光源及投影仪、摄像机具体参数,具有很强的通用性...     

Efficient scheme for the preparation of symmetric Dicke states via cross-Kerr nonlinearity

A scheme is proposed for generating maximally entangled Dicke states among four modes. The scheme only uses Kerr medium and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The scheme can be generalized to produce maximally entangled 2k-qubit states.     

基于改进自适应混沌控制的逆可靠度分析方法

自适应混沌控制方法是一种高效、稳健的逆可靠度分析方法,但在求解强非线性凹功能函数时,计算效率仍然有待提高,且可能会陷入局部最优.通过对混沌控制因子更新策略进行改进,提出了基于改进自适应混沌控制的逆可靠度分析方法.数值算例分析表明:该方法能够有效地改善混沌控制因子自适应选取时的合理性,具有更好的收敛性和更高的计算效率,为结构可靠度分析和可靠度优化问题提供了更加高效、稳健的求解途径.