The high-precision patterning of metal halide perovskites (MHPs) is of paramount importance for their device application. Here, we demonstrate the femtosecond (fs)-laserassisted formation of three-dimensional MHP nanocrystal (NC) patterns with strong blue photoluminescence (PL) inside an oxide glass. Our strategy enables the crystallization and erasing of CsPb(Cl/Br) 3 NCs inside a glass localized around the laser focal area through a combination of fs laser irradiation and thermal treatment processes. These recoverable patterns exhibit a switchable PL associated with the laser-induced defect and the thermal healing of MHP NCs that are benefits from the soft ionic crystal structure and low formation energy of the MHPs. Due to the high stability offered by the protection of the oxide glass matrix, the laser printing of fine-structured MHP micropatterns can be repeated over multiple cycles with a high robustness compared with their colloidal process counterparts. Our results demonstrate a simple strategy for creating emissive patterns inside a stable and transparent solid matrix that could be promising for applications including information storage, three-dimensional displays, anticounterfeit labels, and information security protection.

nanorods) show strong polarized absorption and emission due to the dielectric confinement effect and intrinsic optical anisotropy of their asymmetric shapes. [5][6][7] CsPbBr 3 QD is a cubic crystalline phase with high symmetry at room temperature, resulting in almost no optical anisotropy in the single particle and colloidal solution. [8,9] However, many strategies, such as polymer stretching, electrospinning, nanoimprinting, and photolithography, have been utilized to align semiconductor QDs to generate and improve polarized absorption and emission of semiconductor QDs by implementing orientation arrangement. [10][11][12][13][14][15][16][17] By rotating coating CsPbBr 3 QDs on a silica substrate, the silica substrate induced charge redistribution in CsPbBr 3 QDs, resulting in anisotropic dipole transition distribution and overcoming the population averaging effect to produce polarized emission. [18] Furthermore, It is reported that patterned anti-counterfeiting applications can be achieved by directional recombination of CsPbX 3 (X = Cl, Br, I) nanowires in different directions. [17] Under different polarization excitation, the anti-counterfeiting pattern will present different patterns, because of the PL intensity difference under different polarized angles. Although the above methods can endow CsPbBr 3 QDs with polarization emission 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 CsPbBr 3 quantum dot (QD) line arrays by femtosecond (fs) laser writing in a transparent glass matrix is proposed. The obtained line array structures endow isotropic CsPbBr 3 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 CsPbBr 3 QD line arrays used in anti-counterfeiting can be well maintained in the water environment. The successful demonstration of the laser writing CsPbBr 3 QD polarization structures in glass highlights the versatility of anti-counterfeiting and encryption.

It is well recognized that a widely wavelength‐tunable mid‐infrared (MIR) fiber laser plays an important role in the development of compact and efficient coherent sources in the MIR range. Herein, the optimizing Er/Ho ratio for enhancement of broadband tunable MIR emission covering 2.6‐2.95 μm in the Er3+/Ho3+‐codoped transparent borosilicate glass‐ceramic (GC) fibers containing NaYF4 nanocrystals under 980 nm excitation was investigated. Specifically, the obtained GC fibers with controllable crystallization and well fsd‐maintained structures were prepared by the novel melt‐in‐tube approach. Owing to the effective energy transfer between Er3+ and Ho3+ after crystallization, the 2.7 μm MIR emission was obviously enhanced and the emission region showed a notable extension from 2.6‐2.82 μm to 2.6‐2.95 μm after the addition of Ho3+. Importantly, we conducted a theoretical simulation and calculation related to the MIR laser performance, signifying that the GC fiber may be a promising candidate for MIR fiber laser. Furthermore, the melt‐in‐tube approach will provide a versatile strategy for the preparation of diverse optical functional GC fibers.

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