Abstract
Polarization handling is a key requirement for the next generation of photonic integrated circuits (PICs). Integrated polarization beam splitters (PBS) are central elements for polarization management, but their use in PICs is hindered by poor fabrication tolerances. In this work we present a fully passive, highly fabrication tolerant polarization beam splitter, based on an asymmetrical Mach-Zehnder interferometer (MZI) with a Si/SiO(2) Periodic Layer Structure (PLS) on top of one of its arms. By engineering the birefringence of the PLS we are able to design the MZI arms so that sensitivities to the most critical fabrication errors are greatly reduced. Our PBS design tolerates waveguide width variations of 400nm maintaining a polarization extinction ratio better than 13dB in the complete C-Band.
Highlights
Polarization management in photonic integrated circuits (PICs) is becoming of increasing importance, both to provide polarization transparency [1], and to enable polarization multiplexing in coherent communication systems [2]
polarization beam splitters (PBS) based on directional couplers (DC) and Mach-Zehnder interferometers (MZI) are often the preferred solution as they provide the smallest footprints among the different alternatives
In this work we propose a fully passive MZI based PBS with a periodic layer structure (PLS) on top of one of the MZI arms
Summary
Polarization management in photonic integrated circuits (PICs) is becoming of increasing importance, both to provide polarization transparency [1], and to enable polarization multiplexing in coherent communication systems [2]. The PBSs designs presented to date lack, to the best of our knowledge, the robustness required for satisfactory fabrication yields This sensitivity to fabrication errors affects other polarization handling devices, such as polarization rotators [8, 9]. The most fabrication tolerant, fully passive PBS so far was proposed in [5] It is based on a tapered DC and exhibits a total width tolerance of 100nm. The PLS allows us to design the waveguide birefringence without using metals, so that polarization dependent losses are negligible This approach overcomes the main limitation of asymmetric MZI based PBSs, namely the high sensitivity to width errors in the width of the MZI arms [10, 11]. The device exhibits width tolerances up to 400nm for a polarization extinction ratio of 13dB in the C-Band, thereby providing a four-fold improvement over state-of-the-art passive PBSs
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