An electrically controlled tunable photonic crystal filter based on thin-film lithium niobate

In this paper, we present an electrically controlled tunable narrowband filter based on a thin-film lithium niobate two-dimensional (2D) photonic crystal. The filter incorporates a photonic crystal microcavity structure within the straight waveguide, enabling electronic tuning of the transmitted wavelength through added electrode structures. The optimized microcavity filter design achieves a balance between high transmission rate and quality factor, with a transmission center wavelength of 1 551.6 nm, peak transmission rate of 96.1%, and quality factor of 5 054. Moreover, the filter can shift the central wavelength of the transmission spectrum by applying voltage to the electrodes, with a tuning sensitivity of 13.8 pm/V. The proposed tunable filter adopts a simple-to-fabricate air-hole structure and boasts a compact size (length: 11.57 µm, width: 5.27 µm, area: 60.97 µm²), making it highly suitable for large-scale integration. These features make the filter promising for broad applications in the fields of photonic integration and optical communication.