Oscillator Model Analysis for Slow Light in Bright-Dark-Dark Waveguide Systems

The tunable wideband slow-light based on plasmonic analogue of electromagnetically induced transparency (EIT) in bright-dark-dark mode waveguide systems is investigated in this letter. A three-oscillator model is established to characterize optical responses and slow-light effects in the waveguide systems. The main dependent factors of slow-light effects based on plasmonic analogue of EIT, namely, the cavity-cavity separation and media environment of resonators, are numerically and theoretically discussed in this letter. We find that both the group index and the bandwidth of the slow light in the bright-dark-dark waveguide structures show better performance than those in the normal bright-dark ones. These results suggest that the contradiction between the large group index and the wideband slow light in the bright-dark mode waveguide system can be weakened. At the same time, tunable wideband slow-light effects are also achieved. Our researches may have an application in optical slow-light devices.