Spectral_Engineering_with_CMOS_compatible_SOI_Photonic_Molecules

Photonic systems based on microring resonators have a fundamental constrain given by the strict relationship among free spectral range (FSR), total quality factor (QT) and resonator size, intrinsically making filter spacing, photonic lifetime and footprint interdependent. Here we break this paradigm employing CMOS compatible Silicon-on-Insulator (SOI) photonic molecules based on coupled multiple ring resonators. The resonance wavelengths and their respective linewidths are controlled by the hybridization of the quasi-orthogonal photonic states. We demonstrate photonic molecules with doublet and triplet resonances with spectral spliting only achievable with single rings orders of magnitude larger in foot print. Besides, these splitting are potentially controllable based on the coupling (bonds) between resonators. Finally, the spatial distribution of the hybrid states allows up to sevenfold QT enhancement.