Sinusoidal and rectangular Bragg grating filters: Design, fabrication, and comparative analysis

In this paper, we compare the characteristics of several waveguide Bragg gratings (WBGs) with sinusoidal and rectangular corrugated sidewalls in high confinement integrated optics. Our measurements confirm the performance of both the rectangular and sinusoidal grating as band-rejection filters for TE-polarized signals in the telecom C-band. These measurements demonstrate record high extinction ratios of 35 and 28.91 dB for sinusoidal and rectangular WBGs with a rejection bandwidth as narrow as 4.42 and 6.165 nm. The simulation results and measurements show that the filter bandwidth and coupling coefficient can be changed by altering the corrugation width (ΔW), allowing us to control the filter’s quality factor precisely. The bandwidth of rectangular WBGs drops for ΔW>80 nm, constraining the design of devices requiring broadband WBGs. In contrast, the bandwidth of sinusoidal WBG continues to increase for ΔW>80 nm, providing a wider bandwidth for designers. These findings demonstrate the potential for effective integration of new photonic functionalities into low-footprint electro-optical waveguide tools for sensing, communicating, and computing applications.