Modeling of Loss-Induced Superluminal and Negative Group Velocity in Two-Port Ring-Resonator Circuits

The group velocity vgof light in two-port ring- resonator (TPRR) circuits with loss is theoretically studied. We point out four possible operation regimes, i.e., "slow" light with positive vg, "slow" light with negative vg, "fast" light with negative vg, and "fast" light with positive vg, where "slow" means |vg|g| > c, with c denoting the velocity of light in vacuum. The temporal behavior of pulses passing through the TPRR for the four operation regimes and the potential of "slow" light TPRR either with positive or negative vgfor sensing applications are also discussed.