All‐Optical Switches Based on Erbium‐Doped Thin‐Film Lithium Niobate Waveguides

All‐optical switches are essential building blocks for next‐generation photonic integrated systems. However, achieving a high extinction ratio (ER) in on‐chip integrated devices remains challenging. This study presents a high‐performance all‐optical switch leveraging an erbium‐doped lithium niobate on insulator (Er:LNOI) waveguide. By employing a 1480 nm pump to modulate the absorption and gain states of the waveguide, efficient signal switching across the telecommunication band is realized. The fabricated Er:LNOI device achieves a peak ER of 38 dB within the communication band. This work not only demonstrates a practical solution for high‐performance on‐chip all‐optical control, but also extends the utility of rare‐earth‐doped lithium niobate platforms toward high‐contrast switching systems, paving the way for next‐generation multifunctional photonic integration.