Tunable slow and fast light in double-Lorentzian active fiber Bragg gratings

We proposed a new approach to tunable slow and fast light using double-Lorentzian active fiber Bragg gratings (DL-AFBGs). Group delay in DL-AFBGs is theoretically analyzed using the coupled mode theory. Unique double-Lorentzian spectral resonance of the proposed DL-AFBGs significantly modifies the dispersion of injected light near the Bragg frequency, leading to structure-based tunable slow and fast light. The Bragg frequency varies with the pump power of the FBG. In this way, the group delay of the signal can be optical controlled. Furthermore, we describe a possible realization of group delay tuning from subluminal to superluminal pulse reflection in active double-Lorentzian Bragg gratings. Tunable group delay from 242 ps to −200 ps is theoretically demonstrated. It provides a very simple approach to getting both subluminal and superluminal reflection in one component, which we might find a good future in light matter interaction enhancement, high sensitivity sensor and so on.