Design and analysis of a cascaded microring resonator-based thermo-optical tunable filter with ultralarge free spectrum range and low power consumption

Abstract

A thermo-optical tunable filter based on the Vernier effect of cascaded microring resonators, which can expand the free spectrum range (FSR) and the tuning range, has been designed and simulated. The FSR of the filter with a radius of 48 μm for the first stage and 50 μm for the second stage microring can be expanded to 75.6 nm, which is, at present, the largest FSR to our best knowledge. A tuning range covering all of the above mentioned FSR can be reached under 103.1 mW heating power, which is also the largest one for silicon-based thermo-optical tunable microring resonator filters. The response time, calculated by solving the two-dimensional heat conduction equation with finite element method, of the designed tunable filter with 48/50 μm radius rings is 3.5 μs for the rise edge and 0.8 μs for the fall edge, which is much quicker than most of the reported silicon microring-based thermo-optical tunable filters.