Photothermal-Induced In Situ Crystallization of Perovskite Nanocrystals and the Application on Micro–Nano Defect Detection

Abstract Micro–nano defects on the optical elements are critical factors limiting the maximum light intensity tolerance and system reliability. Developing an accurate and efficient method for defect detection remains a significant technical challenge. Notably, under laser irradiation, defects of varying magnitudes exhibit different photothermal absorption effects, triggering localized photothermal heating. This photothermal effect facilitates the in situ growth of perovskite nanocrystals (NCs) at the defect sites, which could work as fluorescent labeling of defects. Inspired by this phenomenon, we propose a photothermal-induced in situ crystallization method of perovskite NCs. First, the interaction between light and optical materials generates a photothermal effect. Because micro–nano defects have stronger photothermal absorption capabilities, the thermal energy would preferentially accumulate at the defect sites. Once the temperature exceeds a threshold, selective crystallization of perovskite NCs occurs specifically at the defect locations, thereby enabling the fluorescent labeling of defects. This process enables the conversion of optical information from light absorption to fluorescence emission, thus completing the fluorescent labeling and optical imaging of the defects. Optical elements with a surface roughness of 17.48 nm were used to validate the proposed detection method. We also show examples of recognizable nanofabricated features with depths and widths of 100 and 200 nm, respectively. Furthermore, this method exhibits chemical contaminant sensitivity up to 0.039 ppm. The photothermally induced method establishes an optical information conversion mechanism based on light–matter interaction. It shows great potential for quality assessment of optical components.