Coupled Waveguide Polarization Splitter With Slightly Different Core Widths

A coupler-type transverse electric/transverse magnetic (TE/TM) polarization splitter, in which a metal-loaded core is slightly widened, is analyzed using the three-dimensional beam-propagation method. Before analyzing the splitter with the slightly different core widths, the performance of a splitter with two identical cores is evaluated. The use of the two identical cores results in a high crosstalk and a low extinction ratio due to the phase mismatch between the waveguides with and without the metal for the TE mode. Therefore, the core width in the metal-loaded waveguide is slightly widened so as to restore the phase-matching condition. In contrast to the conventional splitter with the two identical cores, the present splitter is found to offer a low crosstalk of less than -30 dB and a high extinction ratio of more than 30 dB with a coupling efficiency of more than 97% at a wavelength of 1.55 mum. In addition, the wideband operation is demonstrated over a wavelength range of 1.50 to 1.61 mum.