Broadband polarization splitter-rotator on a thin-film lithium niobate with conversion-enhanced adiabatic tapers

In this work, we propose and experimentally demonstrate a broadband polarization splitter-rotator (PSR) on the lithium niobate on insulator (LNOI). With multiple sequentially connected adiabatic tapers for waveguide mode conversion and directional coupling, the PSR shows a 160-nm bandwidth covering the C and L bands, an insertion loss of less than 2 dB, and an extinction ratio of more than 11 dB. Benefiting from the conversion-enhanced adiabatic tapers, the broadband device has a short length of 405 mu m. Further optimization is performed to reduce the device length to 271 mu m and comparable performances are achieved, demonstrating the feasibility of higher device compactness. The proposed design and principle can contribute to high-performance polarization management for integrated lithium niobate photonics. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement