Polarization independent Bragg gratings using tilted subwavelength grating waveguide Bragg gratings

We propose and experimentally demonstrate a polarization independent subwavelength grating (SWG) waveguide Bragg grating (WBG) by using an SWG waveguide with tilted segments. By optimizing the tilting angle and other geometry parameters, such as the width and the length of the loading segments used to create the BG, we can obtain a zero birefringence tilted SWG waveguide and consequently, a polarization independent SWG WBG. In our simulations, the optimal tilting angle is similar to 58 degrees, whereas the optimal angle obtained in fabrication is similar to 46 degrees. This deviation is mainly due to fabrication errors, e.g., on the sidewall angle of the silicon segments. For the optimal tilting angle of 46 degrees, the characterized Bragg wavelengths of the TE and TM modes are both similar to 1517 nm. We believe that the proposed device can have applications in optical communications and interconnections.