Low-loss ridge waveguides in thin film lithium niobate-on-insulator (LNOI) fabricated by reactive ion etching

We report on the fabrication of waveguides in 300 nm-thick Y-cut lithium niobate on silicon through optimized reactive ion etching, yielding sidewall roughness of 22.9 nm and propagation losses of 8.62 dB/cm at 1550 nm.