椭偏法细丝在线监测系统设计及数据分析

Ellipsometry design and data analysis of the monitoring system of thin wire on-line measuring

椭圆偏振测量是一种具有原子层级灵敏度的无破坏性光学测量技术 .作者论证了当入射光波长λ及入射光偏振态确定时 ,对应于半径为R的细丝 ,其衍射光强不仅与散射角 φ有关 ,而且与散射场光强分布表现为m阶序列傅里叶变换的序列阶数m有关 ,因而选择 φ和m为测量参数 ;测量系统在连续采样的每一步进中密集采样 ,采用对同一数据点进行重复测量取均值的方法提高采样精度 ;为了提高信噪比 ,对采样数据用曲线拟合最小二乘法进行二次滤波 ;对实测数据进行分析 ,结果表明偏振散射特征及其对散射光场强度分布的影响与散射光在传播过程中偏振度的径向分布有关 .

Measurement with ellipsometry is an optical undamaged measuring technology with a sensibility range of atomic shell. The authors prove that intensity of diffraction light from the thin wire with radius R is related not only to diffusion angle φ but also to order m of Fourier transform spectroscopy expressing the light intensity distribution of diffusion field when the wavelength of incoming light wave to samples is fixed. Both φ and m are chosen as measuring parameters of the monitoring system. Concentrated sampling and averaging method are adopted in any step length of continuous sampling process in order to improve sampling accuracy of a sample point, and digital filtering technique, twice filter based on least square curve fitting are used to raise signal to noise ratio. Finally, the authors demonstrate that diffusion property of polarized light and its influence on light intensity distribution of diffusion field depend on the radial distribution of polarization ratio in the process of diffusion light transmission and point out that gradient curve of polarization ratio is related to the positions.