Integrated Optical Filters Based On Micro-resonators And Reconfigurable Delay Lines

Silicon-based optical filters are important photonic components in optical communication network.Optical filters play an important role in channel selection of the optical communication network and high speed transmission.Silicon microring are widely used to tunable filter.This paper puts forward a new type of microring structure,which can improve the optical filter's performance.In addition,we also puts forward filter based on a reconfigurable delay line.The filter has flexibility and larger bandwidth tunable range.Firstly,we present the theoretical analysis and experimental demonstration of adiabatic microring resonators.The resonators are halfway between microdisk and microring preserving the good properties of both the microdisk(high Q-factor)and the microring(internal mode rejection).Device modeling based on the coupled-mode theory suggests that both the internal and external decay rates should be low in order to obtain high-Q and high extinction ratio resonances.The internal decay is modal-order-dependent and significantly affected by the adiabatic tapering rate of the ring waveguide.The external delay is determined by the modal effective index difference between the bus and ring waveguides at the coupling point under a fixed gap.Upon optimization of the resonator system,two resonance modes in the measured device are measured with one possessing a high Q-factor.Secondly,a reconfigurable optical filter based on a multi-stage delay line is proposed.There are two types of filtering configurations to achieve a tunable bandwidth.One is based on a single delay interference.FSR and bandwidth are tunable via changing the delay time.The other is based on cascaded delay interferences.By changing the coupling ratio of the MZI switches and the number of interference,a tunable bandwidth can be obtained with a constant FSR.The delay interferometer is modeled by using the transfer matrix method.Experimental results of the 2-order and 3-order filters show that the stopband width can be tunable by 1/3 FSR.