Arbitrary on-chip optical filter using complex waveguide Bragg gratings

We demonstrate a Complex Waveguide Bragg Grating (CWBG) which can be designed to generate an arbitrary transmission spectrum. A comprehensive design method, based on the Layer Peeling/Adding algorithm, is developed to realize the grating on a silica-on-silicon platform. The CWBG has a simple one-layer waveguide structure for ease of fabrication. A spectral precision better than +/- 0.1 nm and a suppression ratio between 15 dB and 33 dB are achieved for a transmission spectrum consisting of 20 randomly distributed spectral notches with a 3 dB width of 0.3-0.4 nm. Among the CWBG's various potential applications, we highlight its use for eliminating OH emission lines from the Earth's atmosphere for ground-based astronomical observations. (C) 2016 AIP Publishing LLC.