对于傍轴光束,提出了介质平面波导衍射场的近场模场半宽度、远场发散角半宽度和光束传输因子M2等光束参量之间满足简单的关系式,三个光束参量均可直接由波导模式场分布精确计算,或由可实际精确测量的远场衍射频谱分布精确计算。M2因子的计算公式可表述为以二阶矩和微分算子定义的近场模场半宽度的比值,或以二阶矩和微分算子定义的远场发散角半宽度的比值。最后推导出介质平面波导TE0模衍射场光束参量的解析函数和光束参量的范围。

Based on the condition of paraxial approximation, the simple relational expression among the beam parameters, such as the mode field half width, far field divergence half angle and beam propagation factor M2, in the diffracted field of dielectric planar waveguide TE 0 mode is presented. The beam parameters can be calculated accurately by the mode field distribution of the waveguide, or by the diffraction frequency spectrum distribution in far field which is measurable exactly in the experiment. The calculational formulas of M2 factor are described by the ratio of mode field half widths defined by second moment and differential operator in near field, or the the ratio of far field divergence half angles defined by second moment and differential operator. Finally, the analytic function and scope of the beam parameters in the diffracted field of the dielectric planar waveguide TE 0 mode are demonstrated.