Eight-channel reconfigurable microring filters with tunable frequency, extinction ratio and bandwidth

We demonstrate an eight-channel reconfigurable optical filter on a silicon chip consisting of cascaded microring resonators and integrated compact heaters. With an embedded Mach-Zehnder (MZ) arm coupling to a microring resonator, the important parameters of a filter such as center frequency, extinction ratio and bandwidth can be controlled simultaneously for purposes of filtering, routing and spectral shaping, thus making our method potentially useful in dense wavelength division multiplexing (DWDM) and radio frequency arbitrary waveform generation (RFAWG). Multichannel filter response was successfully tuned to match the International Telecommunication Unit (ITU) grid with 50, 100 and 200GHz in channel spacing. Programmable channel selectivity was demonstrated by heating the MZ arm, and continuous adjustment of through-port extinction ratio from 0dB to 27dB was achieved. Meanwhile, the 3dB bandwidth in the drop port changed from 0.11nm to 0.15nm due to the heating. The device had an ultra-compact footprint (1200\mu mx100\mu m) excluding the metal leads and contact pads, making it suitable for large scale integration.