Bragg Filters for Integrated Photonic Circuitry

We report the design, fabrication, and measurement of waveguide Bragg filters for use in integrated Raman- and fluorescence-based spectroscopy and sensing systems. A periodic effective index was produced by a series of silicon nitride (SiN) patches located adjacent to and on both sides of a straight SiN waveguide. A chirp was applied to the length and spacing of the patches to broaden the reflection bandwidth. The filters were simulated using an eigenmode expansion solver and manufactured at a photonic integrated circuit (PIC) foundry.