Gain-assisted time delay of plasmons in coupled metal ring resonator waveguides.

Coupled metal ring resonator waveguides filled with optical active materials are proposed to achieve the slow light and tunable time delay. The tunable group index and time delay are realized by the dispersion of the active materials and its interplay with that of the geometric structure of the waveguides. Our results from the transfer matrix analysis and finite-difference time-domain numerical simulation show that the anomalous dispersion of the active materials can help to amplify the group index determined by the waveguide geometry. Based upon this structure, a variable-bit-rate optical time-division-multiplexing system is numerically demonstrated.