Design study of ultra-compact sub-wavelength grating polarization rotators in integrated photonics systems

The miniaturization of integrated photonics systems poses higher demands on polarization manipulation devices. An ultracompact sub-wavelength grating polarization rotator is designed using a dual-step structure and multi-segment subwavelength grating layout. Through three-dimensional FDTD numerical simulation and experimental verification, the device achieves a polarization conversion efficiency of 99.8% and an extinction ratio of 48.8 dB at a working wavelength of 1550 nm, with an insertion loss of 0.48 dB and a working bandwidth of 70 nm. The device exhibits good fabrication tolerance, maintaining stable performance within a fabrication error range of ±20 nm for waveguide width and ±15 nm for grating period.