中文摘要：

绝缘体-金属-绝缘体波导支持两种表面等离激元模式，即反对称模和对称模．反对称模的传播长度大，容易被激发．同时其模式尺度大，限制了器件的集成密度．对称模的模式尺度远小于反对称模，却难以被激发．为了应用对称模，提出了模式转换的理念．转换器根据变换光学被设计成均匀的各向异性介质．转换效率可接近80％．

英文摘要：

An insulator-metal-insulator waveguide can support two types of plasmonic waves, namely the anti-symmetric bound （ab） mode and the symmetric bound （sb） mode. The ab mode possesses large propagation length and can be easily launched. However, it also has large mode size, limiting the integration density of plas- monic devices. The sb mode＇ modal size is much smaller than the ab mode; however it is difficult to excite. In or- der to utilizing the sb mode, a concept of mode conversion from the ab mode to the sb mode is proposed. The con- verter is designed to be homogeneous and anisotropic with the assistance of transformation optics. Conversion efficiency of as high as -80% can be realized.