The parallel propagating plane waves can excite both the even and odd defect modes.However, the perpendicularly propagating plane waves can excite only the even mode.

• 当平面波平行于缺陷模耦合方向入射时,可以同时激发奇模和偶模,当入射平面波垂直于耦合方向时,仅产生偶模;