On-chip dual-band waveguide Bragg filter with identical subnanometer-bandwidth stopbands near 1310 and 1950 nm wavelengths

We propose the realization of an on-chip dual identical narrowband Bragg filter at similar to 1310 and similar to 1950 nm wavelengths simultaneously based on the silicon-on-insulator (SOI) platform. By taking advantage of subwavelength corrugation behavior at large wavelengths and the difference in the mode areas of the involved modes at the two widely separated wavelengths, undesired diffraction losses are circumvented while achieving Bragg resonances at the two wavelengths simultaneously. A double-corrugation Bragg grating rib waveguide filter is proposed, with two sets of gratings, the inner one close to the rib operating near 1310 nm wavelength, with the outer grating being designed to achieve a transmission dip around 1950 nm. Introducing a proper lateral misalignment to the set of inner grating indents, a dual identical narrowband Bragg filter with similar to 0.47 nm 3 dB bandwidth at similar to 1310 nm and similar to 1950 nm is achieved. The proposed design strategy based on the SOI platform relies on a single-etching fabrication process and presents potential applications in situations where equal-bandwidth filtering is needed in on-chip communications and sensing. (C) 2021 Optical Society of America