Thin-film lithium niobate-based detector: recent advances and perspectives

Thin-film lithium niobate (TFLN) has emerged as a powerful platform for integrated photonics, offering outstanding electro-optic, nonlinear optical, and ferroelectric properties. These unique material characteristics have opened new opportunities for developing high-performance photodetectors with broad spectral response, high sensitivity, and compact integration. This review provides a comprehensive overview of recent progress in TFLN-based detectors, focusing on the underlying physical mechanisms and diverse device architectures. We first discuss the spontaneous polarization, bulk photovoltaic effect, and pyroelectric effect and frequency up-conversion in lithium niobate, which enable unconventional light-to-electricity conversion without external bias. Then, we introduce heterogeneously integrated photodetectors that combine TFLN with III-V semiconductors, silicon, and two-dimensional materials, under both free-space illumination and waveguide coupling configurations. We further highlight advances in integrating single-photon detectors on TFLN platforms, a key step toward scalable quantum photonic systems. In addition, we discuss the direct modification strategies such as ferroelectric domain engineering, doping, and ion implantation modification to enhance the photodetection performance of TFLN devices. Finally, we summarize the existing challenges and present perspectives on the future development of multifunctional, low-power, and quantum-compatible photodetectors based on the TFLN platform.