Fully tunable optical filter based on a thin-film lithium niobate microring resonator

A fully tunable optical filter on a thin-film lithium niobate platform with a footprint of 2.5 mm × 1.2 mm is demonstrated, in which the extinction ratio, resonant wavelength, and stopband width can be independently and simultaneously adjusted via three integrated electro-optic phase shifters. The device achieves an extinction-ratio tuning range from approximately 0 dB to 31 dB. At maximum extinction ratio, the stopband width can be varied between 8.8 GHz and 9.6 GHz. Moreover, the stopband center wavelength can be shifted linearly with a tuning efficiency of 1.95(8) pm/V. This work provides a compact, electro-optically reconfigurable filter architecture with independent multi-parameter control for on-chip photonic systems.