Optical Modulation of Near-Infrared-Emitting KNN-xNd Transparent Photochromic Ceramics

Transparent photochromic ceramics have attracted significant interest in optical data storage, smart windows, and anti-counterfeiting applications because of their ability to reversibly modulate transparency and color under light stimulation. Near-infrared (NIR) light processing has high practical value in security information protection and communication due to its intrinsic concealment and anti-interference properties. However, optical transparency, photochromic efficiency, and emission tunability are often difficult to optimize simultaneously. This trade-off makes it challenging to integrate these properties into a single material platform. In this study, a series of Nd 3+ -doped K 0.5 Na 0.5 NbO 3 transparent ferroelectric ceramics was fabricated via solid-state synthesis. These ceramics exhibit high transparency and intense NIR emission centered at approximately 1055 nm. Upon ultraviolet (UV) exposure, both optical transmittance and luminescence intensity decrease significantly, yet fully recover after thermal treatment at 150°C, indicating excellent reversibility and repeatability. XPS reveals that oxygen and cation vacancies generate F and V color centers that trap photocarriers and contribute to the observed bidirectional optical modulation. This work demonstrates a promising material system capable of dynamically tuning NIR fluorescence and transparency, offering strong potential for multifunctional optoelectronic devices such as optical switches, secure displays, and rewritable data storage technologies.