High-efficiency Chirped Grating Couplers on Lithium Niobate on Insulator

Chirped grating couplers on lithium niobate on insulator (LNOI) with state-of-the-art theoretical (experimental) coupling efficiencies of 88.7%/coupler (72.0%/coupler) were realized on z-cut LNOI with an Au reflection layer.