Silicon nitride waveguide polarization rotator and polarization beam splitter for chip-scale atomic systems

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Gallacher, Kevin and Griffin, Paul F. and Riis, Erling and Sorel, Marc and Paul, Douglas J. (2022) Silicon nitride waveguide polarization rotator and polarization beam splitter for chip-scale atomic systems. APL Photonics, 7 (4). 046101. ISSN 2378-0967 (https://doi.org/10.1063/5.0077738)

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Abstract

The design, fabrication, and characterization of a silicon nitride waveguide polarization rotator and polarization beam splitter that operate with a polarization extinction ratio (PER) of ∼30 dB at the rubidium atomic transition of 780 nm wavelength are demonstrated. These polarization devices are fabricated on the same chip using a self-aligned process for integration of the rib and ridge waveguide structures. The polarization rotator is based on the mode evolution approach using adiabatic tapers and demonstrates a PER of ≥20 dB over a 100 nm bandwidth (730-830 nm wavelengths) with an insertion loss (IL) ≤1 dB. The polarization beam splitter is based on a cascaded tapered asymmetric directional coupler with phase matching between the fundamental and higher order TM modes, whereas the TE mode is separated by the through port. This provides a PER ≥ 20 dB with IL ≤ 1 dB over a 50 nm bandwidth for the cross port and a PER ≥ 15 dB with an IL ≤ 1 dB over an 18 nm bandwidth for the through port. These polarization control waveguide devices will enable photonic integrated circuits for saturated absorption spectroscopy of atomic vapors for laser stabilization on-chip.

ORCID iDs

Gallacher, Kevin, Griffin, Paul F. ORCID logoORCID: https://orcid.org/0000-0002-0134-7554, Riis, Erling ORCID logoORCID: https://orcid.org/0000-0002-3225-5302, Sorel, Marc and Paul, Douglas J.;
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