Achievement of Large Normalized Delay Bandwidth Product by Exciting Electromagnetic-Induced Transparency in Plasmonic Waveguide

In this paper, we have generated an effect of electromagnetic-induced transparency (EIT)-like transmission in a pair of resonators coupled to a metal-insulator-metal waveguide. Resonators are separated by the metallic nanoslit. By controlling single parameter (i.e., the width of the metallic slit), the device is made to exhibit EIT-like transmission. EIT is the result of destructive interference between two resonating modes, which leads to an asymmetrical-shaped resonance called Fano resonance. EIT is generally accompanied with sharp dispersion that reduces the velocity of light near the resonance. The slow-light characteristics of the device are also investigated. An ultra large value of group index (ng= 117.06) and a large value of normalized delay bandwidth product (NDBP = 0.88) is obtained over an ultra large bandwidth (Δf = 1.39 THz). Furthermore, it is theoretically predicted that asymmetry parameter (q) of Fano resonance experiences a sign reversal when resonances are swept each other in the tuning process. This reversible Fano resonance and slow-light nature of proposed device open up the avenues for designing on-chip optical buffers, switches, modulators, and so on.