Tunable Fano Resonances Based On Microring Resonators

With the exponential increase of the amount of the information in today's society,high speed,large capacity,low power communication scheme need to be urgently put forward.Due to its large capacity,high propagation speed,low-latency,low power consumption,high anti-interference and so on,optical communication network is the most advantageous solution.Optical switch,modulator and filter are the fundamental elements of information processing,exchange and transmission in the optical networks.Therefore,the development of high extinction ratio(ER)switch,filter and modulation is very necessary.Large size Mach-Zehnder switches are detrimental for integration.Compared with the common microring-resonator-based devices,the devices utilizing the asymmetric resonant property have high ER,sensitivity,low power consumption and can be large scale integrated.Research shows that the superposition of the continuous and discrete states can lead to asymmetric Fano resonance.The work will study the Fano resonance in the perspective of silicon photonics: utilizing optical cavities with different cavity length to generate asymmetric Fano resonance.The mutually coupled resonant cavities,namely microring resonator(s)(MRR)and racetrack-like resonator(RTR)formed by one or more semi-rings and a U-shape feedback coupled waveguide(FCW).Herein,the interference between the continuous and discrete states is implemented via couple of the two cavities.A continuous laser beam is input from a port of U-shape waveguide,and the laser will resonate in the two cavities when the laser wavelength is satisfied with the resonant condition of the two cavities.Thus,an asymmetric Fano resonance line-shape can be obtained from the other port of the U-shape waveguide.In addition,the Fano resonance can be periodically tuned via modulating the effective refractive index of the MRR or U-shape FCW based on thermo-optic or electro-optic effect.We experimentally demonstrate the ER of the proposed simple and compact device can achieve as high as 30.8dB,which has many potential applications in the field of optical switching/modulating,filtering,biochemical sensing,etc.