Two-photon absorption flexible photodetector responsive to femtosecond laser

Integrated on-chip femtosecond (fs) laser optoelectronic system, with photodetector as a critical component for light-electrical signal conversion, is a long-sought-after goal for a wide range of frontier applications. However, the high laser peak intensity and complicated nanophotonic waveguide structure of on-chip fs laser are beyond the detectability and integrability of conventional photodetectors. Therefore, flexible photodetector with the response on intense fs laser is in urgent needs. Herein, we demonstrate the first (to our knowledge) two-photon absorption (TPA) flexible photodetector based on the strong TPA nonlinearity of layered hybrid perovskite (IA)₂(MA)₂Pb₃Br₁₀, exhibiting efficient sub-bandgap response on the infrared fs laser at 700-1000 nm. High saturation intensity up to ∼3.8 MW/cm² is achieved. The device also shows superior current stability even after bending for 1000 cycles. This work may pave the new way for the application of flexible optoelectronics specialized in integrated fs-laser detection.