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Perovskite CsPbX3 (X = Cl, Br, I) nanocrystals with advantages of high quantum yield, narrow emission peaks, and tunable fluorescence are considered as the next generation of light‐emitting sources. However, fluorescence degradation due to the poor stability of perovskite nanocrystals in moisture, high temperature, and illumination remains one of the greatest challenges in their further development. In this work, a fully dense coating strategy is proposed to improve the overall stability of perovskite nanocrystals, especially under high‐density laser irradiation. A mesoporous silica SiO2 layer is introduced to construct a stable coating for isolating the perovskite from external environment. To eliminate the pores of the CsPbX3@SiO2, an inorganic glass is also employed via solution‐combustion technique to generate a fully compact encapsulation for further stability promotion. The as‐prepared nanocrystal‐in‐glass composite exhibits efficient and stable fluorescence performance in luminous efficiency, chromaticity, and long‐term reliability in the conditions of thermal shock, humidity, and blue laser irradiation. With the integration of red/green/blue emitting nanocrystals, the color gamut of the white laser lighting source covers 134% of the National Television Standards Committee standard, providing exciting opportunity for high performance laser‐driven white light generation. [ABSTRACT FROM AUTHOR]

Rational design and fabrication of multicolor fluorescent sources represent one of the significant challenges in the development of high‐performance solid‐state lighting, tunable coherent lasing, and full‐color display technologies. However, generation of simultaneous multicolor emission, especially white light generation with a wide color gamut is usually beyond the ability of a single material. Heterogeneous structures made by combinations of red, green, and blue emission building blocks are bulky, inefficient, complicated, and costly. Here reported is a bottom‐up strategy to generate simultaneous multicolor emission with continuous tunability in a single monolithic material based on the "nanocrystals‐in‐glass composite" (NGC) architecture. In this approach, a self‐sustained low‐temperature solution combustion process enables homogeneous solvent dispersion and eventually stable immobilization of multiple nanocrystals in transparent matrix. With transparency of up to 80%, further demonstrated is drawing of fiber from the melt of these combustion‐processed NGC materials. The optical spectra of the as‐drawn glass fiber can be precisely tuned and clustering is effectively suppressed. Moreover, the NGC materials exhibit remarkable anti‐thermal quenching behavior at temperatures of up to 200 °C. The bottom‐up strategy for NGC provides a versatile platform for the fabrication of high‐performance multifunctional fiber‐based devices for advanced applications in lasers, illumination, displaying, and biophotonics. [ABSTRACT FROM AUTHOR]

Applications of trivalent rare earth (RE3+)‐doped light sources in solid‐state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+‐doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration‐mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a "nanocrystals‐in‐glass composite" (NGC) structure. This bottom‐up strategy endows the obtained RE3+‐doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near‐infrared emission from 1300 to 1600 nm, which covers nearly the whole low‐loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high‐performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region. A tunable broadband emission is demonstrated by assembly of ordered rare‐earth‐doped emitters with sequential energy gradient. Migration‐mediated energy quenching has been successfully suppressed by nanoscopic heterogeneous structures constructed in transparent nanocrystals‐in‐glass composites. This assembly strategy highlights the possibility to fabricate multifunctional materials by linking different building units with photonic, magnetic, and electronic properties in a transparent framework. [ABSTRACT FROM AUTHOR]

The pursuit of high‐resolution and advanced anti‐forgery technology has stimulated a growing demand for anti‐counterfeiting and encryption strategies with real‐time response and high security. Polarized patterns taking the advantage of high security, rapid response, simple operation, and great selectivity enable real‐time and non‐invasive detection by monitoring in different polarization directions. Here, a new strategy to design and fabricate the polarized CsPbBr3 quantum dot (QD) line arrays by femtosecond (fs) laser writing in a transparent glass matrix is proposed. The obtained line array structures endow isotropic CsPbBr3 QDs with macroscopic polarized emission with a polarization degree up to 0.189. Through programable design, the authors have created 2D and 3D polarized luminescent patterns made up of vertical and horizontal lines inside the glass for polarization‐sensitive optical anti‐counterfeiting patterns. The CsPbBr3 QD line arrays used in anti‐counterfeiting can be well maintained in the water environment. The successful demonstration of the laser writing CsPbBr3 QD polarization structures in glass highlights the versatility of anti‐counterfeiting and encryption. [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]