Abstract

Filters with narrow bandwidth, high sidelobe suppression ratio (SLSR), and large free spectral range (FSR) play an important role in photonic circuits. In this work, we demonstrate a narrow-band silicon photonic filter using an adiabatic directional coupler (ADC)-assisted subwavelength multimode waveguide Bragg grating (SMWG). The complementary lateral misalignment modulation (CLMM) is applied to realize the apodization for suppressing sidelobes in the filtering spectrum. Two subwavelength corrugations with different widths are designed to achieve a narrow-band filtering spectrum and relieve the requirement of fabrication precision. Experiment results show that a 3-dB bandwidth of 0.51 nm and a SLSR of 16.6 dB are achieved on the CLMM apodized and ADC-assisted SMWG device. An unlimited FSR in the wavelength range of C band is demonstrated as well.