Based on the germanium-on-insulator (GeOI) platform, we numerically demonstrate a photonic polarization rotator (PR) operating in the 2 $\mathrm{\mu }$m waveband. Utilizing the partial-height etching to break the symmetry of germanium waveguide cross section, the proposed PR realizes a 90° polarization rotation between the fundamental transverse electric (TE) and magnetic (TM) modes. The device footprint occupies only 0.4 $\mathrm{\mu }$m $\times 0.4\mathrm{\mu }$m $\times 3\mathrm{\mu }$m. This PR shows a low insertion loss of 0.096 dB, a remarkably high polarization conversion efficiency (PCE) of 98.9%, and an extremely high extinction ratio of 33.45 dB at the wavelength of 2005 nm The PCE keeps above 95.4% within the waveband between 1.9 $\mathrm{\mu }$m and 2.1 $\mathrm{\mu }$m. Furthermore, a reasonable robustness is demonstrated.

基于绝缘体上锗 (GeOI) 平台，我们通过数值演示了在 2 $\mathrm{\mu }$m 波段。利用局部高度蚀刻来打破锗波导截面的对称性，所提出的 PR 实现了基本横向电 (TE) 和磁 (TM) 模式之间的 90° 偏振旋转。器件占地面积仅占 0.4$\mathrm{\mu }$米 $\times 0.4\mathrm{\mu }$米 $\times 3\mathrm{\mu }$米。该 PR 显示出 0.096 dB 的低插入损耗、98.9% 的显着高偏振转换效率 (PCE) 以及 2005 nm 波长下 33.45 dB 的极高消光比。 PCE 在 1.9 之间的波段内保持在 95.4% 以上$\mathrm{\mu }$米和2.1 $\mathrm{\mu }$米。此外，还证明了合理的稳健性。