Polarization Beam Splitter With Different Core Widths and Its Application to Dual-Polarization Optical Hybrid

We investigated the core-width dependence of the birefringence of silica-based waveguides with different relative refractive index differences (Δ), namely a 0.75%-Δ GeO₂-doped waveguide and a 5%-Δ Ta₂O₅-doped waveguide. We revealed that the birefringence of the 0.75%-Δ GeO₂-doped waveguide is almost the same as the stress-induced birefringence and that the 5%-Δ Ta₂O₅-doped waveguide has a large geometrical birefringence. By utilizing the core-width dependence of the birefringence, we have successfully demonstrated a 0.75%-Δ polarization beam splitter (PBS) with an operating wavelength range of more than 150 nm and a dual-polarization optical hybrid including a compact 5%-Δ PBS with a polarization extinction ratio of more than 20 dB over the C-band.