Dionne J A, Sweatlock L A, Atwater H A. Plasmon slot waveguides: Towards chip-scale propagation with subwavelength-scale localization[J]. Phys. Rev. B, 2006, 73(3):035407-1-9.[2] Li G Q, Li X H, Yang H D, et al. Fabrication of colorful metals with femtosecond laser pulses[J]. Chin. Opt.(中国光学), 2011, 4(1):72-76 (in Chinese).[3] Lee T W, Gray S K. Subwavelength light bending by metal slit structures[J]. Opt. Exp., 2005, 13(24):9652-9659.[4] Zhao H, Guang X, Huang J. Novel optical directional coupler based on surface plasmon polaritons[J]. Phys. E, 2008, 40(10):3025-3029.[5] Gao H, Shi H, Wang C, et al. Surface plasmon polariton propagation and combination in Y-shaped metallic channels[J]. Opt. Exp., 2005, 13(26):10795-10800.[6] Han Z, Liu L, Forsberg E. Ultra-compact directional couplers and Mach-Zehnder interferometers employing surface plasmon polaritons[J]. Opt. Commun., 2006, 259(2):690-695.[7] Hossieni A, Massoud Y. A low-loss metal-insulator-metal plasmonic Bragg reflector[J]. Opt. Exp., 2006, 14(23):11318-11323.[8] Liu J, Chen B X, Yang H M. Ion-exchange single-mode stripe waveguide for excitation of surface plasma wave[J]. Opt. Precision Eng.(光学 精密工程), 2011, 19(10):2342-2348 (in Chinese).[9] Lin X S, Huang X G. Tooth-shaped plasmonic waveguide filters with nanometeric sizes[J]. Opt. Lett., 2008, 33(23):2874-2876.[10] Yuan W, Sang M H, Guo Q, et al. Research on narrow band filter of magnetic fluid based on optical waveguide with submillimeter scale[J]. Opt. Precision Eng.(光学 精密工程), 2011, 19(11):2618-2622 (in Chinese).[11] Zhai X, Wen S C, Xiang D, et al. A subwavelength plasmonic waveguide filter with a ring resonator[J]. J. Nanomater., 2013, Article ID 484207, 6 pages, http://dx.doi.org/10.1155/2013/484207.[12] Wang Q R, Li S H, Zheng S L, et al. SPP filters and selectors using nanoscale metal waveguide arrays with bends[J]. Opt. Commun., 2013, 309:282-285.[13] Zheng G G, Chen Y Y, Xu L H, et al. Metal-insulator-metal waveguide-based band-pass filter with circular ring resonator containing Kerr nonlinear medium[J]. Opt. Commun., 2013, 305:164-169.[14] Xiang D, Wang L L, Wang L, et al. Optical transmission through double-layer compound metallic gratings with subwavelength slits[J]. J. Mod. Opt., 2012, 59(15):1342-1348.[15] Gray S K, Kupka T. Propagation of light in metallic nanowire arrays: Finite-difference time-domain studies of silver cylinders[J]. Phys. Rev. B, 2003, 68(4):045415-1-11.[16] Xiang D, Wang L L, Li X F, et al. Transmission resonances of compound metallic gratings with two subwavelength slits in each period[J]. Opt. Exp., 2011, 19(3):2187-2192.