Compact wavelength- and bandwidth-tunable microring modulator.

Fabrication errors currently hold back the large-scale adoption of silicon micro-ring modulators (MRMs). The ability to correct their spectral features post-fabrication is required to enable their commercialization. Here, we report and demonstrate an MRM that uses a tunable two-point coupling scheme, which maintains the MRM's compact footprint (60 µm×45 µm) and allows one to tune the MRM's operating wavelength and adjust the optical bandwidth (and/or extinction ratio). This means that one can compensate for fabrication errors and thereby improve the yields. We confirm the modulator's operation by showing NRZ and PAM-4 modulation, up to 28 Gb/s and 19.9 Gb/s, respectively. Also, the proposed tunable MRM maintains the microring's free-spectral range (FSR), which proves its compatibility for configurable and high-bandwidth DWDM applications.