ABSTRACT Transparent glass composites with high crystallinity (HC‐TGC) exhibit significant potential for applications in nonlinear optics, solid‐state laser systems, and optical information processing technologies. However, achieving HC‐TGC is often hindered by the substantial refractive index mismatch between functional crystals and the glass matrix. To address this challenge, we propose an in situ refractive index buffering strategy. Using LiTaO 3 as a prototype TGC, we controlled the precipitation of a secondary LiAlSi 2 O 6 crystalline phase, which was found to markedly enhance optical transparency. Both the theoretical and experimental analyses reveal that this secondary phase acts as a “refractive index buffer”, effectively reducing the refractive index contrast (Δn) between the LiTaO 3 nanocrystals and the surrounding glass matrix, thereby minimizing light scattering. As a result, we successfully obtained LiTaO 3 TGC with high crystallinity (>85 wt.%) and excellent optical transparency (>70% at 1.5 mm). The composite demonstrates a robust second‐harmonic generation (SHG) response, as well as a unique transverse second‐harmonic generation (TSHG) effect. Furthermore, utilizing this HC‐TGC, we developed a TSHG optical setup and demonstrated its application in monitoring ultrashort optical pulses. This work introduces a generalizable design strategy for creating highly transparent, functional HC‐TGCs, paving the way for advancements in integrated nonlinear photonics.
Tan et al. (2026) studied this question.