Narrow-band Add-Drop Filters Based on Silicon Nitride Multimode Waveguide Bragg Grating

A high-performance silicon nitride based narrow-band multimode waveguide Bragg grating (NBMWBG) add-drop optical filter with high sidelobe suppression ratio (SLSR), low insertion loss and low temperature sensitivity is demonstrated. The complementary lateral-misalignment modulation apodization is introduced to improve the performance of the proposed NBMWBG. Multiple NBMWBGs are cascaded using multiple single-mode interconnected waveguides. The dual-stage and three-stage NBMWBGs are also fabricated and tested. The measured insertion losses, 3-dB bandwidths and SLSRs of single-stage, dual-stage and three-stage NBMWBGs are 0.5 dB, 1 dB and 1.2 dB, 2.3 nm, 2 nm and 1.8 nm, 27.2 dB, 45 dB and 63 dB, respectively. The proposed NBMWBG exhibits a low thermal tuning efficiency of 625 mW/nm. The high SLSR of the three-stage NBMWBG suggests its potential for application in photonic integrated circuits.