High extinction ratio and an ultra-broadband polarization beam splitter in silicon integrated photonics by employing an all-dielectric metamaterial cladding

Abstract

In silicon and other photonic integrated circuit platforms many devices exhibit a large polarization dependency, therefore a polarization beam splitter (PBS) is an essential building block to split optical signal to transversal electric (TE) and transversal magnetic (TM) modes. In this paper we propose a concept of integrated silicon-based PBS exploiting unique properties of all dielectric metamaterial cladding to achieve a high extinction ratio (ER) and wide bandwidth (BW) polarization splitting characteristics. We start from a structure (PBS-1) based on a directional coupler with metamaterial cladding combined with a bent waveguide with metamaterial cladding at the outer side in the role of a TE polarizer at the Thru port of the device. To increase BW we propose the improved concept (PBS-2) - a metamaterial compact dual Mach-Zehnder Interferometer structure in combination with the TE polarizer. Numerical simulations reveal that an exceptionally high ER over 35 dB can be achieved in a BW of 263 nm with insertion loss (IL) below 1 dB in case of PBS-2. The designed device has a footprint of 82 µm. Measurement results reveal that an ER > 30 dB is achievable in a BW of at least 140 nm (limited by the laser tuning range).