Abstract
A polarization splitter and rotator (PSR) based on a tapered directional coupler with relaxed fabrication tolerance is proposed and demonstrated on the silicon-on-insulator platform. The device is simply constructed by parallel-coupling a narrow silicon waveguide with a linearly tapered wider waveguide. Compared to previously reported PSRs based on a normal directional coupler, which suffer from stringent requirements on the accuracy of the narrow waveguide width, the introduced tapered structure of the wide waveguide can be used to compensate the fabrication errors of the narrow waveguide. In addition, only a single step of exposure and etching is needed for the fabrication of the device. Similar high conversion efficiencies are experimentally demonstrated for a narrow waveguide width deviation of 14 nm with large tolerance to the coupler length.
Highlights
Microphotonic circuits built on the silicon-on-insulator (SOI) platform are very promising thanks to their complementary metal oxide semiconductor (CMOS) compatible fabrication processing
Compared to previously reported polarization splitter and rotator (PSR) based on a normal directional coupler, which suffer from stringent requirements on the accuracy of the narrow waveguide width, the introduced tapered structure of the wide waveguide can be used to compensate the fabrication errors of the narrow waveguide
The device is relatively insensitive to fabrication errors of the wide waveguide of the directional coupler (DC), the phase matching condition could still be destroyed by fabrication errors of the narrow waveguide [13]
Summary
Microphotonic circuits built on the silicon-on-insulator (SOI) platform are very promising thanks to their complementary metal oxide semiconductor (CMOS) compatible fabrication processing Their high refractive indices enable bending radii of SOI wires down to a few micrometers with negligible bending loss, leading to extremely compact optical circuits [1]. The device is relatively insensitive to fabrication errors of the wide waveguide of the DC, the phase matching condition could still be destroyed by fabrication errors of the narrow waveguide [13] Another similar PSR has been proposed relying on mode conversion from the TM0 to the TE1 mode by an adiabatic taper and from TE1 to TE0 mode by an asymmetrical DC [16]. The sensitivity to the length of the DC is efficiently relaxed
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