High Coupling-Efficiency Ridge-Waveguide Gratings on Single Crystal Thin-Film Lithium Niobate (TFLN)

The uniform ridge-waveguide grating couplers in TFLN are fabricated. All the structures in the device are monolithically patterned by electron-beam lithography. Single coupler exhibits an ultra-high coupling efficiency of -6.5 dB at 1546 nm.