Bandwidth-tunable, FSR-free, microring-based, SOI filter with integrated contra-directional couplers

A silicon-on-insulator (SOI), bandwidth (BW)-tunable, free-spectral-range (FSR)-free, microring resonator (MRR)-based filter is experimentally demonstrated. The device achieves an FSR-free response at its through and drop ports by using a grating-assisted coupler in one coupling region of the MRR and achieves a non-adjacent channel isolation, (nA ), for 400 GHz WDM, greater than 26.7 dB. A thermally tunable Mach-Zehnder Interferometer-based coupling scheme is also utilized to compensate for fabrication variations and enable the BW tunability of the filter. The BW of the filter can be continuously tuned from 25 to 60 GHz while maintaining an nA greater than 26.7 dB.