High Extinction Ratio Polarization Beam Splitter Realized by Separately Coupling

A novel compact polarization beam splitter (PBS) based on a triple-waveguide directional coupler is presented. Among these three waveguides, the middle one is regarded as an input where the contrast of effective refractive index between fundamental modes is enhanced with dielectric-loaded waveguide. Confined into the waveguides with coupling lengths of
$8.3~\mu \text{m}$
(TM) and
$9.9~\mu $
m (TE) on both sides, the two fundamental modes are separately coupled. In virtue of the separated coupling structure, a high polarization extinction ratio (PER) of 45.6 dB together with a low insertion loss (< 0.3 dB) for TE mode, and meanwhile a moderate PER of 20.0 dB with an insertion loss of (< 0.1 dB) for TM mode are achieved at around
$1.55~\mu \text{m}$
. Furthermore, the operation bandwidth of this PBS, during which the PER is higher than 40 dB, is up to 80 nm for TE mode.