Narrowband Tunable Optical Filter with An Arch-Like Configuration Using SOI Platform

We propose and demonstrate a low-loss optical bandpass filter with a narrow bandwidth and a steep roll-off, which is based on three feed-forward silicon microring resonators (MRRs). Using the scattering matrix method, we elaborate the simulation model and spectral response analysis of our proposed filter, thereby determining the geometric parameters of the proposed optical filter. Moreover, we compare its performance with different MRR-based filters composed of three ring cavities. Our proposed filter exhibits a different spectral line shape, lower insertion loss and a distinct roll-off feature for the same target 3dB bandwidth. As a proof of concept, we fabricate the proposed optical filter on a silicon-on-insulator (SOI) platform. The device exhibits a 3dB bandwidth of
$\sim 25$
GHz @1550nm and an on-chip loss of -2.5 dB. Additionally, at the transition band points -10 dB and -20 dB lower than the passband center, we observe a roll-off rate of
$\sim 45$
dB/nm. Compared with traditional high-order MRRs, our scheme has lower fabrication accuracy requirements and produces lower thermal crosstalk.