Metasurface‐Enhanced Photodetection in Lithium Niobate

Abstract Lithium niobate on insulators (LNOI) is a versatile platform for integrated photonics, yet the development of photodetectors is hindered by LN's wide bandgap and the lack of a PN‐junction, which is essential for conventional photodetection mechanisms. Existing methods, such as exploiting transitions between the conduction band and defect levels within the LN bandgap under an external electric field, are limited by weak light‐matter interactions, reducing their efficiency. In this work, a metasurface‐enhanced LN photodetector is demonstrated, in which structural resonance amplifies local electric fields and significantly boosts photocurrent generation. By tuning the resonance of the metasurface to match the 532 nm excitation wavelength, a 26‐fold enhancement in photocurrent is achieved compared to unstructured LN films. This work presents a novel approach for improving LN‐based photodetectors, enabling the development of integrated photonic systems that combine nonlinear optics, electro‐optic modulation, and efficient photodetection on a single LN platform.