Defect Engineering of Nanocrystal-In-Glass Composites for Ultrashort Optical Pulse Monitoring

The rational control of intrinsic defects in materials can significantly enhance their scientific and technological potentials, but it remains a long-standing challenge in nanocrystal-in-glass composites (NGCs). Herein, a defect engineering strategy mediated by the mixed alkali effect is proposed and experimentally demonstrated for NGCs. Interestingly, the hybridization of large alkali ions can effectively increase the barrier of Li + migration and reduce the Li-related defects in LiNbO 3 NGC. As a result, a novel LiNbO 3 NGC with greatly reduced Li-related defects, high crystallinity of over 60%, and excellent optical transmission are successfully fabricated. This unique NGC configuration facilitates efficient transverse second harmonic generation (TSHG) in a broad wavelength region. Based on the above effects, a standard TSHG device is fabricated and implemented to monitor ultrashort optical pulses with duration in the order of ≈10 −13 s over a broad wavelength region, down to 780 nm. The proposed strategy not only provides a new idea for defect engineering in materials science but also has great significance for boosting the practical applications of NGCs in ultrashort optical pulse monitoring.