Combination of Surface Plasmon Polaritons and Subwavelength Grating for Polarization Beam Splitting

A polarization beam splitter (PBS) based on the plasmonic subwavelength grating (PSWG) is proposed and investigated. The PBS is composed by a directional coupler with a PSWG as the coupling region, which offers additional freedom for index tailoring. The mode properties are strongly modified by the unique structure of the PSWG resulting in selective coupling with the two polarization states in the neighbor waveguides. The calculations show that the insertion loss of PBS is less than 1 dB, and the extinction ratios of transverse electric and transverse magnetic polarizations are as high as 27 dB and 30 dB respectively with nearly 4-μm coupling region length. In addition, the fabrication tolerance of the device is investigated in detail.