Vertically Coupled Silicon Nitride Microdisk Resonant Filters

Polarization-dependent vertically coupled microdisk resonant filters are experimentally demonstrated based on a multilayer silicon nitride platform. An improved planarization technique based on conventional chemical-mechanical polishing and dry-etching is adopted to flatten the gap film surface for a different core layer deposition after the first-layer photonic circuit is formed. The resonator can realize a high quality factor (> 10⁴) and large suppression value (>20 dB) for the transverse electric light, while the transverse magnetic wave has weak resonant coupling. Other vertically coupled multifunctional devices can be further expected based on the current integration method. A cascaded resonator filter with superior characteristics, such as a flat passband, a steep roll-off, and an enhanced suppression ratio is developed.