Sub-micron scale polarization beam splitter with high performances using dielectric materials

To satisfy the ever-increasing transmission demands of optical communications, a polarization division multiplexing (PDM) offers an efficient solution in manipulating optical signals for photonic integrated circuits (PICs). In between, a polarization beam splitter (PBS), which can separate transverse-electric (TE) and transverse-magnetic (TM) modes, is most important devices for PDM and allows the two polarization modes to be processed independently, doubling the traffic bandwidth. For assessing the performances of a PBS, some criteria include device dimension, polarization extinction ratio (PER), insertion loss (IL), and operating bandwidth. Among these factors, the most essential one might minimize PBS dimensions while retaining satisfactory device performance. As a result, we report an ultrashort polarization beam splitter (PBS) based on Silicon (Si) waveguides in this work. Different from a conventional plasmonic waveguide,the present PBS using only dielectric materials avoids the high ohmic loss. The proposed PBS are composed of two jointed Si waveguides. The transverse-electric (TE) and transverse-magnetic (TM) modes are separated by a straight wide Si waveguide and a slanted narrow Si waveguide, respectively, without relying on an additional coupling region. As a result, this design considerably reduces the length of the PBS to the submicron scale of 600nm (the shortest PBS with dielectrics reported to date is about 2 µm) while offering polarization extinction ratios (PERs) of ∼22 dB for the two modes and insertion losses (ILs) of ∼ 0.4 dB (∼ 0.8 dB) for the TE (TM) mode. The operating band is over a broad band of 200nm (from ⋋ = 1450nm to 1650 nm) while the two modes have PERs of greater than 20 dB. The reported design is beneficial for offering a high density integrated photonic circuits.