“…Metal-insulator-metal (MIM) structures can propagate SPPs at the subwavelength dimensions with light confinement properties [4]. So, these structures have been used in many applications such as Mach-Zehnder interferometers [5][6][7][8], Bragg reflectors [9,10], demultiplexers [11,12], sensors [13][14][15][16][17][18], modulators [19], filters [20,21], and optical switches [22,23]. Plasmonic filters based on the MIM waveguide structures provide effective solutions for comparatively high propagation loss due to large size [24].…”