Doubly resonant distributed feedback cavity with controllable wide wavelength separation

A double corrugation quarterly wavelength shifted (QWS) distributed feedback (DFB) Bragg grating cavity which includes two sets of Bragg gratings located at different positions away from a waveguide center is proposed. It can support two wavelength-far-separated resonances, for instance 735 nm and 1310 nm as an illustrative example of the proposed flexible approach applied to a silicon nitride rib waveguide. Based on the proposed design principle, the two sets of Bragg distributed corrugations operate nearly independently, diffraction losses being minimized by design principle even though these two resonances are widely separated. The proposed approach of a double corrugation cavity that relies on a single-etching fabrication process, fits with the need of situations where two simultaneous widely spaced resonances are required, with potential for applications to on-chip amplification, lasing, second harmonic generation, and nonlinear optical process in hybrid integrated waveguides.