Ultrashort polarization rotator based on cross-symmetry waveguide

•Novel cross-symmetric structure is put forward.•The conversion length of the presented PR is as short as 3.3 μm.•The extinction ratio is 27.7 dB (TE–TM) and 35.9 dB(TM–TE).•The insertion loss is as low as 0.28 dB.

An ultrashort polarization rotator (PR) based on cross-symmetry waveguide is proposed and discussed. At the operating wavelength of 1.55μm, the presented PR has a small conversion length of 3.3μm. The polarization conversion efficiency (PCE) is 99.8%99.8% (TE–TM) and 99.97%99.97% (TM–TE). The PR can achieve rather high conversion efficiency (>97%>97%) over a broad bandwidth (1450−1700nm). The cross-symmetry structure can significantly improve the extinction ratio. The extinction ratio is 27.7dB (TE–TM) and 35.9dB (TM–TE) with the insertion loss of 0.28dB. The fabrication tolerances for the waveguide for both transverse and horizontal directions are also studied.