Scalable Bandwidth-Tunable Micro-Ring Filter Based on Multi-Channel-Spectrum Combination

We propose and experimentally demonstrate a scalable bandwidth-tunable bandpass filter on silicon. Its spectrum is combined by that of four channels and each channel is formed by two cascaded micro-ring resonators (MRRs). By tuning the center wavelength spacing of the eight MRRs and the phase shifts of four channels, a wide bandwidth tuning range from 37.5 GHz to 227.5 GHz can be achieved with a shape factor between 0.2 and 0.73 and an in-band ripple less than 1 dB. By comparing with the performance of three-channel and two-channel structures, we can draw the conclusion that inducing more channels can effectively improve the bandwidth tunability. The filter also has a wide free spectral range (about 1.2 THz) and small footprint (0.12 mm
²
).