Design and Performance Study of a Compact SOI Polarization Rotator at 1.55 μm

We numerically design a compact silicon (Si) based polarization rotator (PR) by exploiting power coupling through phase matching between the TM mode of a Si strip waveguide (WG) and TE mode of a Si-air vertical slot WG. In such structures, the coupling occurs due to horizontal structural asymmetries and extremely high modal hybridness due to high refractive index contrast of Si-on-insulator (SOI) structure. Design parameters of the coupler have been optimized to achieve a compact PR of ~135 μm length at the telecommunication wavelength of 1.55 μm. Maximum power coupling efficiency Cm, which is studied by examining the transmittance of light, is achieved as high as 80% for both polarization conversions. Fabrication tolerances and the band width of operation of the designed PR have also been studied.