以有机聚合物非对称脊波导为研究对象，采用半矢量有限差分光束传输法(FD-BPM)，系统地分析了不同脊高、脊宽和芯层平板短侧宽度条件下非对称脊形波导的基模截止和单模条件。得出：在芯层高度一定的情况下，基模截止区域和单模区域均随脊高或脊宽的缩小而增大，单模区域随脊形波导芯层平板短侧宽度s的减小而减小；其尺寸以选择芯层厚度h≥1.5 μm，脊高(H-h)≤0.4 μm，脊宽4 μm≤w≤8 μm，芯层平板短侧宽度s=2 μm较佳。研究表明，非对称脊波导单模条件区域仍能满足实际应用要求。

The fundamental mode cut-off and single-mode conditions of asymmetric ridge waveguide under different ridge heights, ridge widths and the short side widths of core plate are systematically studied in semi-vector finite-difference beam propagation method (FD-BPM) with organic polymer asymmetric ridge waveguide as the object. The result shows that both fundamental mode cut-off area and single-mode area increase with reduction of ridge height and ridge width while single-mode area decreases with reduction of short side width of core plate at a certain core height. The structure is optimized as core height h≥1.5 μm, ridge height (H-h)≤0.4 μm, ridge width 4 μm≤w≤8 μm, short side width s=2 μm. The research shows that the single-mode area of asymmetric ridge waveguide meets requirements of practical application.