We demonstrate a broadband grating couplers which can be fabricated on SOI by MPW process. By using chirped grating coupler, broad-bandwidth of 78 nm with 1 dB insertion and 130 nm with 3 dB insertion are achieved.
A multi-layer polarization rotator is proposed and demonstrated based on inverse design. Simulation results show that the device successfully rotates the polarization state of the input light from TE to TM with a coupling length of only 2.8 um, and the insertion loss and extinction ratio are 3.29 dB and 25 dB respectively at the wavelength of 1550 nm. Besides, the device has a fairly-wide operating bandwidth of 64 nm from 1506 nm to 1570 nm.