A compact polarization rotator (PR) with an asymmetric single dielectric loaded rib waveguide is proposed. The core of the waveguide is designed to have a specific rectangular configuration. The waveguide requires only a single asymmetrical dielectric loading on the core to complete the polarization conversion. The optical field is confined to the vicinity of the core center, which matches the optical field of the input/output waveguides. The transition loss of the PR is as low as 0.03-0.21 dB/facet without the taper or offset schemes. Such results can facilitate the fabrication of a PR with an operating length of 10 μm. In a comprehensively designed PR with a length of 7.92 μm, a -1 dB bandwidth for polarization conversion efficiency (PCE) is greater than 100 nm at the communicating wavelength of 1550 nm. The loading width and thickness with ±20 nm tolerance exhibit -0.87 and -0.49 dB changes in PCE, respectively.