Self-action of Counterpropagating Axially Symmetric Light Beams in a Transparent Cubic-nonlinearity Medium

Abstract

The stationary effect of self-action of counterpropagating axially symmetric light beams in a medium with cubic nonlinearity is discussed. Self-similar solutions for initial radiation parameters and nonlinear medium characteristics in the case of slowly varying amplitudes of beams are found. The analysis of approximate solutions obtained on the basis of motion constants is carried out and results are compared with numerical experimental data.     

Light steering of Air-Gaussian beam in Nonlocal Nonlinear Medium

With a nonlocal model, we investigate the propagation dynamics of a single Airy–Gaussian (AiG) beam and their interaction in one-dimensional condition by means of direct numerical simulations. With the split-step Fourier method, numerical results show that nonlocality can support periodic intensity distribution of AiG beams leading to the formation of stable bound states. Espesically, by tuning the phase difference between the two beams, we can steer the centre of the bound AiG beams in nonlocal nonlinear media.     

光束偏振的高精度实时检测技术

针对光束的偏振形态,本文设计了一种新型的光束偏振实时检测系统,该系统利用特殊设计的分光片和相位分光镜将被测入射光束分为四路的方法实现了光束偏振状态的实时测量。系统中添加有优化器件可调相位补偿器,用以优化系统仪器矩阵。系统具备优化功能,优化理论和公式被推导和给出。给出了一种理想的仪器矩阵,并实现了该系统,与理想偏差小于0.25%。系统具备优化功能,结构简单,对该系统的偏振检测能力进行了分析和测试,实验结果表明系统测试精度可达97%。     

光纤型偏振OCT 系统中光偏振特性的研究

建立了偏振光在生物组织中传播的模型,并利用该模型模拟了偏振光在生物组织中传播的过程,重建了多种偏振态输入光的情况下光偏振态在生物组织中的分布及生物组织的偏振特性模型.分析了光偏振度与光被生物组织散射次数的关系,阐明了由于偏振光在组织中传播,其偏振态逐渐改变而造成的偏振OCT 干涉计两臂光束失去相干性及偏振OCT 图像质量下降现象.通过分析斯托克斯(Stokes)矢量和穆勒(Muller)矩阵在光纤型偏振OCT系统中的应用,说明Muller 矩阵不受输入光偏振态的影响,因此它比Stokes 矢量更适用于光纤型偏振OCT 系统研究.     

Second-order Coherence Effects Due to the Superposition of Two Independent Thermal Light Beams

A photon-coincidence counting technique has been used to observe the second-order coherence in a plane receiving light from two small incoherently illuminated apertures. Measurements made for two wavelengths, 546·1 and 435·8 nm, gave results consistent with predictions from the van Cittert-Zernike theorem.     

基于面结构光的无效相位区域补偿算法

针对面结构光三维测量中投影盲区导致出现无效相位区域的问题,提出了一种无效相位区域补偿方法.根据光栅投影法重建原理可知,无效区域的主值相位为参考平面对应的主值相位值.首先,由投影仪投射一幅具有均匀光强的白光图到被测钢板表面,使用CCD相机采集钢板表面背景图;其次,对其进行二值化,得到无效相位区域位置;然后,通过背景相位图替换,得到无效相位的真实相位,完成无效相位区域的补偿;最后,对一块带孔洞的钢板进行三维重建,对比分析无效相位区域补偿前后的孔洞直径测量结果.实验证明,无效相位区域补偿后孔洞测量精度为0.1 mm,补偿前孔洞测量精度结果为0.3 mm,因此该方法改善了阴影盲区导致的孔洞直径测量误差较大的缺点,在一定程度上提高了孔洞直径的测量精度.     

The Effects of Optical Properties on Thin Films on Polarization and Intensity of Light Diffracted through Wide Angles

The effect of the edge material and the wavelength on wide-angle diffraction was investigated with a sensitive photomultiplier photometer. Measurements of as little as 10^?8 fraction of the incident light at an angle of 70° showed the effect on the intensity and polarization of the diffracted light due to the nature of the edge material and depending on the wavelength used.     

接触式表面轮廓测量的非线性误差分析与补偿

测量触针随杠杆绕支点转动产生圆弧轨迹,其水平方向位移偏差会对大量程接触式表面轮廓测量形成误差。在改进传统测杆结构的基础上,建立了测量结果的非线性误差数学模型,推导出多项式拟合误差的补偿算法。提出了拟合标准球计算误差补偿参数的方法。通过对半径为79.505 3mm的球冠测量,得到半径尺寸误差小于1μm,实验证明了取得了较好的补偿效果。     

基于白光干涉仪对卷烟包装材料外观质量的评价

目的 建立评价卷烟包装材料外观质量的检测方法,用于对卷烟包装材料的表面印刷适用性进行预判,以提高印刷效率。方法 以水雾面积作为对卷烟包装材料外观质量的主要评价对象,筛选卷烟包装材料印刷面的表观特性。对烟标表面粗糙度、平滑度、亮度、摩擦因数、粗糙度、表面形貌与水雾面积的相关性进行分析。结果 卷烟包装材料外观质量（水雾面积）与粗糙度、亮度等参数相关,与平滑度、摩擦因数等参数不直接相关。在433～818 nm的微观粗糙度内,水雾面积随着粗糙度的增加逐渐减小,当微观粗糙度大于818 nm时,水雾现象不存在。结论 基于白光干涉仪的微观粗糙度可作为卷烟包装材料外观质量（水雾现象）的定量和定性评价指标,该方法为解决烟包印刷行业的水雾问题提供了有益的理论支持。     

Influence of Light Polarization on the Behaviour of a Resonant Cascade Laser

A cascade laser model based on a J = 0 M J = 1 M J = 0 ladder atomic-level scheme is proposed. The cases of relative parallel and orthogonal linear field polarizations are studied. The parallel configuration reduces to a three-level cascade laser model in the limit of minimal Zeeman-coherence relaxation rate. Contrarily, the absence of two-photon processes in the orthogonal configuration makes this case equivalent to a pair of incoherently coupled two-level laser models. The stability properties and dynamic behaviour of the orthogonal configuration are analysed.     

氦离子辐照下钨纳米丝的自保护行为

采用低能量(200 eV)大流强的He⁺辐照多晶钨材料,辐照温度为1023 K和1373 K,辐照剂量为1.0×10²⁵~1.0×10²⁶ ions/m²。用称重、扫描电子显微镜、导电原子力显微镜等手段分析辐照后钨材料的质量损失、表面形貌和内表面缺陷分布,研究了刻蚀速率与表面形貌的关系。结果表明,具有粗糙钨纳米丝表面的钨样品刻蚀速率只有平滑表面的30%。其原因是,在大流强He⁺辐照下钨表面纳米丝的形成阻碍钨原子的溅射。这也意味着,钨纳米丝表面的形成可作为钨材料的自保护结构层,抑制ITER相关辐照下的强刻蚀。     

Analysis of a Fibre-optic Ring Resonator with Polarization Effects: Application to Polarization Sensing with Improved Sensitivity

Abstract

A theoretical analysis for a fibre-optic ring resonator is given by assuming a polarization modulation in the loop fibre. If the change in polarization angle θ in the loop is large, the output intensity has two resonance dips separated in phase by an angle equal to 2θ, when the loop phase is scanned from 0 to 2π. When θ is small, the resonator output produces only one resonance dip and the amplitude of this resonance dip is a measure of θ. By placing a polarizer at the resonator output, a resonance peak in the intensity is produced with an amplitude that increases with increasing θ. Such a system has potential applications, for example, in Faraday current sensing, with an increased sensitivity. The effects of birefringence in the loop and the angle of polarization of the input light are also analysed.     

利用自然光做面光源拍照凸面客体上痕迹

对柱面、球面等凸面物体上痕迹的拍照,一直是刑事照相专业的难点之一。利用自然光做面光源配光,在凸面客体上形成大于痕迹面积的光斑,进行定向反射照相,可以有效解决部分拍照凸面客体上痕迹难题。