Simultaneous Enhancement of Bandwidth and Group Index of Slow Light via Metamaterial Induced Transparency With Double Bright Resonators

We propose a design strategy to alleviate the tradeoff between the wide frequency band and large group index of metamaterial induced slow light. It is realized with a structure consisting of double bright resonators and a single dark resonator in each unit cell. Such a structure enables the slow light with enhanced bandwidth and increased group index simultaneously than the conventional scheme with only one bright resonator. The origin is attributed to the stronger bright-dark coupling and steeper dispersion in the double bright structure. The slow light characteristics are analytically demonstrated with the coupled oscillator model and verified by the full-wave simulations. The presented design rule may offer an avenue to realize broadband slow light devices.