Add–drop filter with complex waveguide Bragg grating and multimode interferometer operating on arbitrarily spaced channels

Abstract

We present a silicon nitride/silicon dioxide add-drop filter operating on arbitrarily spaced channels using multimode interferometers (MMIs) and complex waveguide Bragg gratings (CWBGs). The add-drop filter shows a rejection ratio of >40 dB on all five channels, with a line width of 1.2 nm and an on-chip loss of <1 dB. By designing the CWBG with the Layer Peeling/Layer Adding algorithm, this MMI-CWBG add-drop filter platform has the capability for ultrabroadband add-drop operation on arbitrarily spaced channels.