Integrated Subwavelength Gratings on a Lithium Niobate on Insulator Platform for Mode and Polarization Manipulation

Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits, with fast-growing toolbox of components. This paper proposes, designs, and experimentally demonstrates compact subwavelength grating (SWG) waveguides an LNOI on-chip mode polarization manipulation. To overcome the limitation waveguide fabrication, SWGs are designed formed silicon nitride thin film deposited onto surface chip. As proof-of-concept devices, SWG-based spatial filters (including TE1-mode-pass filter TE2-mode-pass filter) TM-pass polarizer fabricated successfully same chip, device lengths only ≈50 μm. The measured insertion losses devices lower than 3.1 dB, high extinction ratio larger 30 at wavelength 1550 nm. proposed demonstrated can serve important building blocks in series handling photonics.