Experimental demonstration of a low-loss low-reflectivity TM-pass polarizer based on tilted subwavelength metamaterials

The silicon-on-insulator platform exhibits strong birefringence, often requiring single-polarization operation to ensure the optimal performance of integrated photonic systems. On-chip polarizers that suppress unwanted polarization states are key in this scenario. Achieving efficient TE-mode suppression with low-loss TM transmission is particularly challenging on the standard 220 nm silicon platform because of the stronger confinement of the TE mode compared to the TM mode. In this work, we experimentally demonstrate a TM-pass polarizer fabricated on a standard 220 nm silicon platform with a single etch step. By leveraging subwavelength metamaterials, we engineer a Bragg grating that reflects the fundamental TE mode into the first-order TE mode, which is radiated away, while allowing the TM mode to pass with minimal loss. The device achieves a measured extinction ratio exceeding 20 dB and insertion losses below 1 dB across a bandwidth of 170 nm, with a total footprint of 17.84 µm by 1.1 µm. We furthermore demonstrate, for the first time, to our knowledge, in Bragg–based polarizers, measured back-reflections for TE polarization below −18.9dB.