Silicon photonic polarization beam splitter assisted by polarization-Selective metamaterials with 600 nm bandwidth

Abstract

Silicon photonic polarization beam splitter (PBS) is a crucial component for on-chip polarization management. PBSs typically function based on wavelength-dependent mechanisms such as evanescent coupling and modal interference. As a result, constructing a PBS with a broad bandwidth, low insertion loss, and high extinction ratio remains a significant challenge. This paper presents a novel method for achieving a PBS that is almost independent of the wavelength, which involves engineering the modal birefringence of subwavelength grating waveguides and utilizing reciprocal mode transitions. An input taper is embedded in polarization-selective metamaterials (PSMs), which are made up of two sets of subwavelength gratings arranged in different directions. As the width of the input taper decreases, the waveguide mode is no longer supported and transits into a single-mode-like (SML) component guided in the SWG waveguide. By exploiting the principle that a mode will preferentially evolve into the mode with the closest effective refractive index, polarization beam splitting is achieved during the transition of waveguide modes into SML components guided in SWGs with different arrangement directions. Results show that the proposed PBS achieves a high extinction ratio of more than 23 dB throughout a bandwidth of 600 nm (1.2–1.8 μm) for both polarizations. For TE/TM polarization, the bandwidth to achieve an insertion loss of lower than 0.41/1 dB is as large as 600 nm (1.2–1.8 μm)/530 nm (1.23–1.76 μm). As far as we know, this is the PBS with the most superior broadband performance proposed till now.