Lithium niobate on insulator (LNOI) has emerged as an ideal platform for photonic integration due to its superior electro-optic properties, strong nonlinearities, and low optical loss. This work presents an LNOI-based TE-pass polarizer with subwavelength gratings that overcomes the critical limitations of conventional polarizers—high insertion loss (IL) and narrow bandwidth. The device consists of the input straight waveguide, the metawaveguide, and the subwavelength gratings. By designing the metawaveguide width to match the effective refractive indices, the input TM mode is converted into a TE mode and subsequently leaks laterally through the side subwavelength gratings. Simulation results indicate a polarization extinction ratio (PER) of 32 dB with an IL below 0.46 dB, maintaining a PER $>20\mathrm{dB}$ across a 24 nm range. Experimentally, the device achieves a 28.6 dB PER and maintains a PER $>15\mathrm{dB}$ over a 71 nm bandwidth. Notably, a cascaded configuration of three identical devices maintains an ultracompact footprint ($<660\mu \mathrm{m}$ length). This breakthrough performance establishes our design as an optimal solution for polarization management in high-density photonic integration.

Close

PrevNext

View figure in article

• Integrated optics
• Nanophotonics
• Waveguides