Lee Young Jong
Opt Express. 2018 Sep 17;26(19):24577-24590. doi: 10.1364/OE.26.024577.
A non-tomographic analysis method is proposed to determine the 3D angles and the order parameter of molecular orientation using polarization-dependent infrared (IR) spectroscopy. Conventional polarization-based imaging approaches provide only 2D-projected orientational information of single vibrational modes. The newly proposed method concurrently analyses polarization angle-dependent absorptance of two non-parallel transition dipole moments. The relative phase angle and the maximum-to-minimum ratios observed from the two polarization profiles are used to calculate the 3D angles of the mean molecular orientation and the order parameter of the orientational distribution. Usage of those relative observables as intermediate input parameters makes the analysis results robust against variations in concentration, thickness, absorption peak, and absorption cross-section, which can occur in typical imaging conditions. This analysis is based on a single-step, non-iterative calculation that does not require any analytical model function of an orientational distribution function. This concurrent polarization analysis method is demonstrated using two simulation data examples, followed by associated error propagation analysis and discussion on the effect of absorption strength. Application of this robust spectral analysis method to polarization IR microscopy will provide a full molecular orientation image without tilting that tomographies require.
提出了一种非断层分析方法，用于利用偏振相关红外（IR）光谱确定分子取向的三维角度和序参量。传统的基于偏振的成像方法仅提供单一振动模式的二维投影取向信息。新提出的方法同时分析两个非平行跃迁偶极矩的偏振角相关吸收率。从两个偏振分布中观察到的相对相位角和最大与最小比率用于计算平均分子取向的三维角度和取向分布的序参量。将这些相对可观测量用作中间输入参数，使得分析结果对于典型成像条件下可能出现的浓度、厚度、吸收峰和吸收截面的变化具有鲁棒性。该分析基于单步、非迭代计算，不需要取向分布函数的任何解析模型函数。使用两个模拟数据示例演示了这种并发偏振分析方法，随后进行了相关的误差传播分析以及关于吸收强度影响的讨论。将这种鲁棒的光谱分析方法应用于偏振红外显微镜将提供无需断层扫描所需倾斜的完整分子取向图像。
