Subwavelength engineering and asymmetry: two efficient tools for sub-nanometer-bandwidth silicon Bragg filters

• Published in: Optics letters Vol. 43; no. 14; p. 3208
• Main Authors: Oser, Dorian, Pérez-Galacho, Diego, Alonso-Ramos, Carlos, Le Roux, Xavier, Tanzilli, Sébastien, Vivien, Laurent, Labonté, Laurent, Cassan, Éric
• Format: Journal Article
• Language: English
• Published: United States 15.07.2018
• ISSN: 1539-4794
• DOI: 10.1364/OL.43.003208

Bragg filters stand as key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we show that the combination of single-side corrugation asymmetry and subwavelength engineering provides a narrowband response with large corrugations, overcoming minimum feature size constraints of conventional Si Bragg filters. We comprehensively study the impact of the corrugation asymmetry in conventional and subwavelength single-etched SOI Bragg filters, showing their potential for bandwidth reduction. Finally, we experimentally demonstrate novel subwavelength geometry based on shifted corrugation teeth, achieving null-to-null bandwidths and rejections of 0.8 nm and 40 dB for the symmetric configuration and 0.6 nm and 15 dB for the asymmetric case.