An efficient and compact mid-infrared polarization splitter and rotator based on a bifurcated tapered-bent waveguide

We present predictive simulations for a novel mid-infrared (MIR) polarization splitter and rotator (PSR) design. It operates in the 3.1–3.6 m range, which is crucial for applications such as chemical and biological sensing, and environmental monitoring. This is the first report of a MIR PSR in this range on a SOI platform, enabling the generation of TE modes at both ports of the PSR. Our solution is particularly important since quantum cascade lasers are the optimal choice of source in the MIR, emitting linearly polarized light in the vertical direction that couples to transverse magnetic (TM) waveguide modes, necessitating conversion to transverse electric (TE) mode for compatibility with numerous on-chip devices optimized for TE mode. Our proposed PSR is designed to provide both TE modes at both ports of the bifurcated waveguide, showcasing outstanding performance characterized by low insertion loss, low TM to TE power conversion loss, and minimal crosstalk. It exhibits TE insertion loss and TM to TE power conversion loss of less than 0.5 dB over a 500 nm and 400 nm wavelength range, respectively, while maintaining crosstalk values below 20 dB over a broad wavelength range of 400 nm.