Synchronous and Controllable Realization of Lorentzian, Fano, and Electromagnetically Induced Transparency Lineshapes in an All-Fiber System

We demonstrate an all-fiber approach to synchronous and controllable excitation of Lorentzian, Fano, and electromagnetically induced transparency (EIT) lineshapes. A microfiber knot resonator (MKR) is embedded into one arm of a fiber-based Mach-Zehnder interferometer (MZI), in which the discrete comb-like resonance of MKR can interfere with the continuous interference spectrum of MZI to simultaneously excite the three distinct resonance lineshapes. In the system, the controllable loop diameter of MKR and optical path difference of MZI offer high flexibility and adjustability to Fano lineshape characteristics including asymmetry, spectral range and free spectral range between adjacent resonances. Furthermore, when a slight temperature modulation less than 1 °C is applied to the system, the Fano resonance can undergo a complete periodic change, causing lineshapes to convert sequentially for each profile, and the spectral information is transformed into the amplified color barcode to clearly describe the small temperature variation. The Fano resonance generation system exhibits significant promise in enhancing fiber-based devices and extending the applications of Fano resonance in optical switch and high-sensitive sensing.