Silicon-based polarization-insensitive optical filter with dual-gratings

A silicon-based polarization-insensitive optical filter is proposed and demonstrated. For the present on-chip polarization-insensitive optical filter, there is a dual-polarization mode (de)multiplexer, a TE-type multimode waveguide grating (MWG) with triangular corrugations and a TM-type MWG with rectangular corrugations. Here the triangular corrugations are introduced to reduce the undesired reflection and suppress the Fabry-Parot resonance. Furthermore, lateral shift apodization is introduced for both two types of MWGs to suppress the side lobes. For the fabricated device, the measured 3 dB-bandwidth is as large as similar to 11 nm and the excess loss is similar to 1.5 dB for both polarizations, while the sidelobe suppression ratios are 23 dB and 17 dB for TE and TM polarizations, respectively. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement