从三层平板波导麦克斯韦方程的模场解出发,根据光斑尺寸的定义,讨论了波导模式,波导尺寸、折射率差、工作波长以及波导非对称性对光斑尺寸的影响,给出了最小光斑的波导条件。分析和模拟结果表明,对称三层平板波导TE模的最小光斑尺寸(MMSS)与波导芯/包层介电系数差的平方根成反比,TM模最小光斑尺寸则依赖于波导芯层和包层介电系数的具体大小,相同波导结构条件下TM模的等效光斑尺寸较TE模更大,二者皆与工作波长成正比;非对称波导中光斑分布是非对称的,其光斑尺寸介于分别以两个包层为包层的对应对称三层平板波导之间,其最小光斑尺寸随对称因子的增大先减小后增大。 Based on the field solutions of the Maxwell equation of the three-layer slab waveguide, the effects of the waveguide mode, the waveguide size, the refractive index difference, the working wavelength and the waveguide asymmetry on the spot size are discussed according to the definition of the spot size. Waveguide conditions. The analysis and simulation results show that the minimum spot size (MMSS) of the TE mode of the symmetric three-layer slab waveguide is inversely proportional to the square root of the difference of the dielectric coefficient between the waveguide core and the cladding. The minimum spot size of the TM mode depends on the waveguide core layer and the cladding layer The specific size of the electric coefficient, the equivalent waveguide spot size of the TM mode is larger than that of the TE mode under the same waveguide structure, both of which are directly proportional to the working wavelength; the spot distribution in the asymmetric waveguide is asymmetric and the spot size is between Between the two cladding layers, corresponding to the symmetrical three-layer slab waveguide, the minimum spot size first decreases and then increases with the increase of the symmetry factor.