Programmable Optical Filter in Thin-Film Lithium Niobate with Simultaneous Tunability of Extinction Ratio and Wavelength

On-chip optical filters are of key importance to many modern applications such as optical interconnections and wavelength division multiplexing systems. In all these scenarios, simultaneous tunability of the extinction ratio and working wavelength is particularly essential for the optical filters to construct the optical networks but remains a scientific challenge. Here, we demonstrate a novel optical filter on the thin-film lithium niobate platform, where both the extinction ratio and working wavelength can be simultaneously and independently tuned by adjusting two loaded electro-optic modulators. The device demonstrates the tunability of the extinction ratio from 0 to over 25 dB at a fixed working wavelength. On the other hand, the filter, with a footprint of 1.2 mm × 0.65 mm, also shows over 100 pm linewidth with a resonant wavelength tunability of 12.5 pm/V at the critical coupling condition.