Metal-insulator-metal plasmonic waveguide for low-distortion slow light at telecom frequencies

We propose metal-insulator-metal (MIM) plasmonic waveguide, in which metal is aluminum-doped zinc oxide (AZO) and insulator is air. The real part of relative dielectric constant is negative that is similar to the metal. Therefore, we call the AZO as metal. Owing to cutoff frequency of TM₀ model for the MIM waveguide being slightly larger than 193.5?THz, the MIM waveguide shows obviously slow light effect around the commonly used telecom frequency. Exploiting the dispersion relationship of MIM waveguide, we analyze the effect of core layer width for the MIM waveguide on slow group velocity, second-, and third-order dispersion. The core layer width of MIM waveguide is determined to simultaneously realize obviously slow light effect and the lower distortion for the pulse with width 200?fs, which is confirmed by simulation used the finite-difference time-domain method. The MIM waveguide potentially applied in optical delay lines is easily fabricated.