两种模场半宽的定义在计算角向偏移损耗中的误差比较

Comparison of Errors Resulted from Calculating Tilt Loss by Two Mode-Field-Half-Width Definitions

本文提出了任意折射率分布单模平面光波导模场半宽的近场二阶矩定义ω_(BMS),导出了角向偏移损耗的准确式、近场二阶矩定义下的近似式及其误差估计式。对阶跃对称单模平面光波导的计算表明:在常用工作参数范围内,当归一化角向偏移量较小时,用ω_(BMS)算得的角向偏移损耗比用高斯最小二乘拟合模场半宽算得的结果更准,而且用误差估计式来估算用W_(BMS)计算角向偏移损耗的误差是合适的。

In this paper, the near-field-second-moment-definition (NFSMD) wkms of mode-field-half-width (MFHW) for single-mode planar waveguide with arbitrary index profile is proposed, and various formulas for tilt loss calculation between two identical planar optical waveguides are presented, including 'accurate' values, approximate values based on NFSMD wkms, and its error estimation. Nummerical data for symmetric step-index planar optical waveguides shows that under small normalized tilt angular and usually working parameters, the tilt loss calculated from wkms is more accurate compared with that from the Gaussian least-mean-square fit MFHW, and error estimation formula can be used to estimate the error of tilt loss approximate values based on wkms..