Thin-film lithium niobate based microwave photonic filter with up to 110 GHz tuning range

Integrated microwave photonic filters (MPFs) are essential components for enabling broadband radio frequency signal processing. However, owing to the deficiency of large-bandwidth electro-optic (EO) modulation devices, traditional integrated MPFs based on III-V or silicon photonic platforms face significant challenges in achieving ultra-wideband operation, particularly when extending to the V/E bands and sub-terahertz range. In this paper, we address this limitation and experimentally demonstrated an integrated MPF with ultra-wideband tunability exceeding 110 GHz and high filtering resolution at the sub-GHz level, based on a monolithic thin-film lithium niobate (TFLN) platform. The TFLN MPF chip comprises a large-bandwidth phase modulator and a low-loss microring resonator (MRR) with an intrinsic Q of 2.62 × 10⁶, achieving bandpass filtering responses based on phase-modulation to intensity modulation (PM-IM) conversion mechanism. By precisely controlling the wavelength deviation between the laser carrier and microring resonance, this MPF achieves continuous tuning of the center frequency from near DC to 110 GHz, while maintaining narrow filtering bandwidth (<350 MHz) across the entire tuning range. Compared to state-of-the-art integrated solutions, the proposed TFLN MPF improves the filtering tunable range by nearly two times and extends the operating frequency of MPF beyond 110 GHz for the first time. Our work establishes a foundation for future millimeter-wave and sub-terahertz applications, ranging from 6G ultra-high-speed wireless communication to high-resolution radar.