Abstract
We demonstrate a compact silicon polarization beam splitter (PBS) based on grating-assisted contradirectional couplers (GACCs). Over 30-dB extinction ratios and less than 1-dB insertion losses are achieved for both polarizations. The proposed PBS exhibits tolerance in width variation, and the polarization extinction ratios remain higher than 20 dB for both polarizations when the width variation is adjusted from + 10 to -10 nm. Benefiting from the enhanced coupling by the GACCs, the polarization extinction ratio can be kept higher than 15 dB and the insertion loss is lower than 2 dB for both polarizations when the coupling length varies from 30.96 to 13.76 μm.
Highlights
Silicon nanowire waveguides with high index-contrast between core and cladding generally have high birefringence values, which result in polarization mode dispersion and polarization dependent loss [1,2,3]
These results show that, as the coupling length varies from 30.96 μm to 13.76 μm, the Polarization extinction ratios (PERs) still remain higher than 15 dB and the insertion losses are lower than 2 dB for both polarizations, which demonstrates that the polarization beam splitter (PBS) are insensitive to coupling length variations
We have experimentally demonstrated a compact silicon PBS based on grating-assisted contradirectional couplers (GACCs)
Summary
Silicon nanowire waveguides with high index-contrast between core and cladding generally have high birefringence values, which result in polarization mode dispersion and polarization dependent loss [1,2,3]. The optical coupling between two waveguides in the DC-based PBS was periodically dependent on the coupling length and sensitive to fabrication variations. A compact PBS based on asymmetrical grating-assisted contradirectional couplers (GACCs) was theoretically proposed [24]. An advantage of such PBS is that it does not require stringent phase matching and coupling length conditions. We perform a detailed study of a high-extinction-ratio PBS in terms of design, fabrication, and tolerance to width and coupling length variations. To the best of our knowledge, our device achieves record high PERs with large tolerance in waveguide width and coupling length variations
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