Lanthanide-Doped Transparent Glass-Ceramics: Enabling Compact Laser Sources through Nanostructure Engineering

Lanthanide-doped transparent glass-ceramics (GCs) have emerged as versatile gain media by combining the spectroscopic advantages of crystalline hosts with the processing flexibility of amorphous glasses. Through controlled precipitation of nanoscale crystals, GCs provide tailored local environments for lanthanide ions while maintaining optical transparency and glass-based fabrication advantages, providing opportunities for compact and wavelength-tailored laser sources. This Spotlight on Applications reviews recent advances in lanthanide-doped transparent GCs for application-oriented laser technologies, with particular emphasis on whispering-gallery-mode microcavity lasers and fiber lasers. By correlating fabrication strategies, microstructural evolution, and optical performance, we highlight how nanocrystal engineering regulates optical gain and enables laser operation across visible, near-infrared, and ∼2 μm spectral regions. The roles of crystal size control, crystal-glass interface engineering, and dopant redistribution in balancing spectroscopic enhancement and optical losses are further discussed. Remaining challenges in predictive crystallization control, low-loss device fabrication, and scalable integration are summarized, together with future opportunities for developing compact, wavelength-diverse, and multifunctional photonic laser platforms.