investigating the characteristics of a double circular ring resonators slow light device based on the plasmonics-induced transparency coupled with metal-dielectric-metal waveguide system

We have numerically investigated an analog of electromagnetically induced transparency (eit) in a metal-dielectric-metal (mdm) waveguide bend. the geometry consists of two asymmetrical stubs extending parallel to an arm of a straight mdm waveguide bend. finite-difference time-domain simulations show that a transparent window is located at 1550 nm, which is the phenomenon of plasmonic-induced transparency (pit). signal wavelength is assumed to be 820 nm. the velocity of the plasmonic mode can be largely slowed down while propagating along the mdm bends. multiple-peak plasmon-induced transparency can be realized by cascading multiple cavities with different lengths and suitable cavity-cavity separations. large group index up to 73 can be obtained at the pit window. our proposed configuration thus be applied to storing and stopping light in plasmonic waveguide bends. in addition, the relationship between the transmission characteristics and the geometric parameters including the radius of the nano-ring, the coupling distance, and the deviation length between the stub and the nano-ring is studied in a step further. the velocity of the plasmonic mode can be largely slowed down while propagating along the mdm bends. for indirect coupling, formation of transparency window is determined by resonance detuning, but, evolution of transparency is mainly attributed to the change of the coupling distance. theoretical results provide a guideline for control of light in highly integrated optical circuits. the characteristics of our plasmonic system indicate a significant potential application in integrated optical circuits such as optical storage, ultrafast plasmonic switch, highly performance filter, and slow light devices.