We present a multifunctional microwave photonic chip on an x-cut thin-film lithium niobate (TFLN) platform that monolithically integrates an ultrabroadband electro-optic phase modulator and a thermally tunable phase-shifted Bragg grating (PSBG). The PSBG provides a single narrowband defect mode without a free spectral range limitation, enabling high-selectivity and continuously tunable on-chip microwave photonic filtering. The phase modulator exhibits a 3-dB electro-optic bandwidth exceeding 67 GHz with a VπL of 2.95 V cm, while the optimized PSBG provides a linewidth of ∼6 pm and an extinction ratio above 20–30 dB under stable thermo-optic tuning. Using this integrated architecture, we demonstrate a tunable integrated microwave photonic filter with continuous frequency tuning from 1 to 65 GHz and a measured RF bandwidth of ∼890 MHz. We further realize an on-chip optoelectronic oscillator by forming a hybrid optoelectronic feedback loop, achieving a side-mode suppression ratio of 41 dB and a short-term frequency drift of 22.8 kHz. This work establishes a versatile and scalable approach to integrated microwave photonic signal processing, enabling broadband tunability, narrowband filtering, and low-noise microwave generation on a single TFLN chip.
Zhang et al. (2026) studied this question.