Abstract
We propose and experimentally demonstrate an ultra-compact and highly efficient polarization splitter and rotator based on a silicon bent directional coupler structure. The TM-to-TE cross-polarization coupling occurs between the two parallel bent waveguides, if the phase matching condition is satisfied. Efficient polarization splitting and rotating are simultaneously achieved. The device is fabricated by a single step of exposure and etching. The measured peak TM-to-TE polarization conversion efficiency reaches 96.9%. The TM-to-TE conversion loss is lower than 1 dB in the wavelength range of 1544 nm–1585 nm, and the insertion loss for the TE polarization is lower than 0.3 dB in the wavelength regime of 1530 nm–1600 nm. The cross talk values are lower than −20 and −18 dB for the TE- and TM-polarizations over a wavelength range of 70 nm, respectively. The coupling length of the polarization splitter and rotator is 8.77μm. To the best of our knowledge, our device achieves the shortest coupling length.
Highlights
Silicon photonics on a silicon-on-insulator (SOI) platform has attracted much attention in the past decades[1,2] due to the advantages of compact footprint, low power consumption, and compatibility with the complementary metal-oxide-semiconductor (CMOS) process
Many types of siliconwaveguide polarization beam splitters (PBSs) and PSRs have been reported based on various structures, including directional coupler,[9,10] multimode interference (MMI),[11] hybrid plasmonic waveguide,[12] grating,[13] photonic crystal,[14] and so on
The TM-to-TE cross-polarization coupling occurs between two parallel silicon bent waveguides
Summary
Silicon photonics on a silicon-on-insulator (SOI) platform has attracted much attention in the past decades[1,2] due to the advantages of compact footprint, low power consumption, and compatibility with the complementary metal-oxide-semiconductor (CMOS) process. In order to realize a fabricationerror tolerant PSR, a tapered directional coupler was applied.[15] Similar high polarization conversion efficiencies were obtained in the device with a coupling length of 140 μm.
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