Ultracompact, high extinction ratio polarization beam splitter-rotator based on hybrid plasmonic-dielectric directional coupling.

A polarization beam splitter-rotator based on asymmetric directional coupling is proposed. An ultrashort cross-polarization coupling length of 7.7 μm is achieved by manipulating the optical field distribution via the plasmonic effect, which is the shortest one reported so far, to the best of our knowledge. At the wavelength of 1.55 μm, the extinction ratios are as high as 50.9 dB and 28.2 dB for fundamental transverse magnetic (TM) and transverse electric (TE) polarizations, respectively, and the corresponding insertion losses are 1.545 dB and 0.037 dB. In addition, the TM-to-TE polarization conversion efficiency is higher than 95% within a bandwidth of 70 nm.