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Transparent nanocrystal-in-glass composite (NGC) comprising functional nanocrystals in transparent inorganic glass creates a new bridging from nano/microscale structure to multifunctional macroscale devices with advanced optical properties. In this review, we outline the key scientific advances in the development of transparent NGC, from the perspectives of fundamental design principles, new synthetic strategies and their substantial progress in advanced optical applications. To generate desired transparent NGC materials, we start with the design principles to describe the transformation process from nano/micro to macro, providing an in-depth insight into the structure-property relationship and the underlying problem in particle binding and network reconstruction in the composite materials. Emerging techniques based on the "top-down" or "bottom-up" strategies have advanced the ability to fabricate nanocomposites with controllable composition, phases, fraction, morphology, spatial distribution, and orientation. We also provide an overview of recent advances in optical applications, including solid-state lighting, high-performance lasers, optical data storage, and fluorescence sensing. The remaining scientific challenges, for example, the important trade-off between functional performance and chemical compatibility when bridging the nanocrystals to transparent NGC and their devices, are also highlighted. Addressing these questions will provide a clear pathway to design and manufacture multifunctional inorganic materials based on these NGC materials. [ABSTRACT FROM AUTHOR]

Transparent glass ceramics (GCs) consisting of an homogeneous glass phase and a well‐dispersed crystal phase are considered as ideal optical gain materials potentially applied in optoelectronic devices due to the combination of facile processability of glass and the intense crystal field of nanocrystals. Here, a heat‐induced nanocrystal‐in‐glass method is employed to integrate the active ions Tm3+ into Bi2Te4O11 nanocrystals with an intense crystal field to realize an enhanced microlaser output. This strategy endows the efficient tellurate GC microcavity laser operating at ≈2 µm. Compared with the laser properties of as‐prepared glass microcavities, the pump threshold (260 µW) is as low as less than a quarter and the slope efficiency (0.0296%) is 5.5 times higher. Furthermore, by carefully engineering the heat treatment temperature and duration, the crystal size and distribution can be precisely controlled. Thus, the Rayleigh scattering loss that is detrimental to quality (Q) factor is effectively suppressed and the GC microcavities with high Q factors up to 105 are successfully obtained. This work provides useful insight on the development of optical functional materials and expands the practical applications of GC microcavities in various optoelectronic fields. [ABSTRACT FROM AUTHOR]

Nanocrystallized glass ceramics (NGCs) are important optical materials, but few studies have focused on their laser actions. Here, by precipitation of NaYF4 nanocrystals enriched with Er3+ ions in an oxide glass matrix, great enhancement of the luminescence properties for the NGC microspheres is realized. By carefully matching the refractive index of the glass matrix with that of the NaYF4 nanocrystals and controlling the size and distribution of the precipitated nanocrystals, the absorption and Rayleigh scattering losses that are harmful to quality (Q) factors are efficiently suppressed. As a result, the NGC microsphere cavities present ultrahigh Q factors up to 106 (@ 1610 nm), which is slightly lower than that of the microsphere cavities made by precursor glass. Moreover, single mode whispering gallery modes (WGMs) lasing from the NGC microsphere cavities for the first time is successfully realized. Compared with the microsphere cavity based on glass, the NGC microsphere cavity exhibits large enhancement of the pumping efficiency by more than 7 times and a decrease in the threshold by more than 2.5 times. The results demonstrated here suggest a novel method for improving the laser output performances of microcavities, which may have potential applications in areas of photonics and optical communication. [ABSTRACT FROM AUTHOR]