Integrated Tunable High‐Q Fabry‐Pérot Cavity

ABSTRACT Fabry‐Pérot cavities are widely utilized in optical communication systems and laser technologies. Monolithically integrated reflectivity‐tunable Fabry‐Pérot cavities still face significant challenges, particularly in achieving low‐loss transmission and high tuning efficiency mechanisms. In this work, we demonstrate an on‐chip reflectivity‐tunable Fabry‐Pérot cavity through integration of the Mach‐Zehnder interferometer and Sagnac loop mirror on thin‐film lithium niobate substrate. This F‐P cavity achieves the Q factor of 2.5 × 10 5 at 1553.26 nm along with the reflectivity modulation contrast of 17.5 dB. These results establish a critical foundation for on‐chip high‐ performance laser.