TE/TM-pass polarizers based on the lithium niobate–silicon nitride
hybrid platform are numerically proposed for the first time, to the
best of our knowledge. By utilizing the lateral leakage of a shallowly
etched rib waveguide, 1-mm-long TE/TM-pass polarizers with high
extinction ratios of 28.72/24.03 dB are obtained. Because of the
anisotropy of the lithium niobate, the lateral leakage of TE/TM
polarization modes can occur along crystallographic
z
/
y
directions, respectively. Such
TE/TM-pass polarizers can be integrated in the same wafer.
We propose a novel optical 1×2 power splitter based on an asymmetric ladder-shaped multimode interference (MMI) coupler in silicon-on-insulator (SOI) which has an ultra-compact size of 3.3 µm×2.4 µm. A trapezoid with a small region is removed from the bottom left corner of the MMI coupler to achieve variable splitting ratio. The comparison with the asymmetric rectangular 1×2 splitter is numerically analyzed. By carefully optimizing the width of input taper, the proposed splitter shows a low phase deviation for the two output ports while keeping both of a low-loss performance and feasible splitting ratio. The simulated results show that the splitter can operate with an insertion loss less than 0.67 dB, a large range of splitting ratio from 50:50 to 11:89 and an ultra-low phase deviation less than 2.8° among the C band spectra.
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