A fabrication-tolerant mid-infrared silicon polarization splitter and rotator (PSR) based on a partially etched grating-assisted coupler is proposed. The design of the partially etched structure allows to use different cladding layers, such as SiO2, to make the device compatible with the metal back-end of line process. Moreover, by using the grating-assisted coupler, the device is no longer limited by the precise requirement of the coupling length and strength as those in its counterparts based

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... on directional couplers. The simulation results show that the PSR can work over a wide spectral range of 50 nm around the mid-infrared wavelength of 2.5 µm with the typical TE-to-TM polarization conversion efficiency of 96.83%, conversion loss of -0.97 dB and polarization crosstalk of -21.48 dB. The TM-to-TM through insertion loss is around -0.76 dB. The effects of the fabrication errors are analyzed. The numerical simulation results demonstrate that the device has a good fabrication tolerance larger than 45 nm. Index Terms-Silicon on insulator (SOI), polarization splitter and rotator, grating-assisted coupler, mid-infrared