Design of a Mid-Infrared Bandpass Filter With Large Rejection Bandwidth for Silicon Photonics

In this paper, we propose and numerically investigate a novel concept for a mid-infrared bandpass filter based on a single stepwise linearly chirped Bragg grating, which can be used to create narrowband emitters in the mid-infrared region. We devised the filter on a silicon platform for a transmission wavelength of 4.26 μm, which can be used for carbon dioxide sensing. In order to comply with industrial design rules, we limited the resolution of the design grid to 1 nm, which made it necessary to repeat each individual grating pitch in order to optimize the performance. The devised filter features a transmission band of 100 nm, tailored to the absorption band of carbon dioxide, in combination with a spectrally broad rejection band.