Novel Slow-Light Reflector Composed of a Fiber Ring Resonator and Low-Reflectivity Fiber Bragg Grating

Slow-light components are attractive for many practical applications, such as narrow linewidth lasers and optical delay line. Characteristics of a novel slow-light reflector, which is composed of a fiber resonator and an extremely low reflectivity fiber Bragg grating (LRFBG), are proposed and analyzed theoretically and experimentally. Due to the light recirculating propagation in the fiber resonator by using a low split ratio coupler, the LRFBG inserted ring provides not only high reflectivity, but also an enlarged group delay, which shows a good slow-light property. In our research, the effective reflectance up to unity can be obtained when the FBG reflectivity and coupler split ratio reach to the critical values for lossless cases. Double peak resonant effects are also observed when the reflectivity of FBG is larger than the critical value. A supernarrow-linewidth fiber laser using the proposed slow-light reflector as its output cavity mirror is built experimentally to verify the analyzed results. It is believed that the proposed slow-light component will have some good applications due to the merits of compactness and low cost.