Search

Flexible regulation of bandgap of perovskite nanocrystals (PNCs) is fundamentally critical for desirable optoelectronic functions and applications. Here, regulating chemical composition and emission wavelength of PNCs in glass by a simple heat‐treatment process are reported, which is established to rely on the thermal‐trigger phase separation and ion exchange. The first principle calculations are overall performed to reveal the mechanism of bandgap engineering and optimization of emission performance. The PNCs exhibit excellent stability against thermal, ultraviolet irradiation, and organic molecules. The bandgap of PNCs in the heat‐treated glass can also be re‐modulated by ultrafast laser irradiation. Ultrafast laser direct writing of multi‐color patterns and holographic dynamic displays are achieved, which hold great potential in the application of encryption‐decryption and emissive devices. [ABSTRACT FROM AUTHOR]

Wavelength conversion based on hybrid inorganic–organic sensitized triplet–triplet annihilation upconversion (TTA‐UC) is promising for applications such as photovoltaics, light‐emitting‐diodes, photocatalysis, additive manufacturing, and bioimaging. The efficiency of TTA‐UC depends on the population of triplet excitons involved in triplet energy transfer (TET), the driving force in TET, and the coupling strength between the donor and acceptor. Consequently, achieving highly efficient TTA‐UC necessitates the precise control of the electronic states of inorganic donors. However, conventional covalently bonded nanocrystals (NCs) face significant challenges in this regard. Herein, a novel strategy to exert control over electronic states is proposed, thereby enhancing TET and TTA‐UC by incorporating ionic‐bonded CsPbBr3 and lanthanide Ce3+ ions into composite NCs. These composite‐NCs exhibit high photoluminescence quantum yield, extended single‐exciton lifetime, quantum confinement, and uplifted energy levels. This engineering strategy of electronic states engendered a comprehensive impact, augmenting the population of triplet excitons participating in the TET process, enhancing coupling strength and the driving force, ultimately leading to an unconventional, dopant concentration‐dependent nonlinear enhancement of UC efficiency. This work not only advances fundamental understanding of hybrid TTA‐UC but also opens a door for the creation of other ionic‐bonded composite NCs with tunable functionalities, promising innovations for next‐generation optoelectronic applications. [ABSTRACT FROM AUTHOR]

Chemical engineering in lead halide perovskite nanocrystals (PNCs) has garnered significant attention for tailoring optoelectronic properties, such as bandgap, quantum yield (QY), and stability. Here, pure blue emissive PNCs in glass by using ultrafast laser are reported. The emission wavelength is tuned in the range from 461 to 520 nm by engineering the chemical composition in the B‐site Cd/Pb mix‐cation system. The photoluminescence (PL) QY of CsCdxPb1−xBr3 PNCs reaches 13.4% for the pure blue emission at 467 nm, which is twice that of CsPbBryCl3−y PNCs. The pure blue emissive PNCs exhibit remarkable stability when exposed to ultraviolet (UV) radiation, heat, and ethanol solvents. The ultrafast laser print patterns can be encrypted and decrypted for information, which shows great potential for crucial information security applications. These results imply that B‐site engineering for lead halide PNCs embedded in glass is effective to tailor the PL spectra and increase the PL QY. The pure blue emissive PNCs hold great potential in the applications of blue and full‐color emissive devices. [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]

Rare earth (RE) ions‐doped luminescent nanocrystals (NCs) with numerous unique advantages have attracted tremendous interest for the wide applications from science to engineering, yet suffering from the shortcoming of thermal quenching coming from surface organic ligands. We propose utilizing a facile acid‐base reaction to remove surface organic ligands introduced choosing carboxylic acids as stabilizing agent and weaken thermal quenching. The results showed that the acid‐base reaction displayed an outstanding cleaning effect. After acid‐treatment, most surface organic ligands were removed, and there was no influence on crystal structure and morphology of as‐prepared β‐NaYF4:Er3+ NCs. Meanwhile, with no surface organic ligands capping, β‐NaYF4:Er3+ NCs preferred brighter emission after thermal treatment, including up‐conversion (UC), near‐infrared (NIR), and mid‐infrared (MIR) emission. When calcined the acid‐treated β‐NaYF4:Er3+ NCs in different atmosphere, such as oxygen and reducing atmosphere (15%H2 + 85%N2), an unexpected enhancement of all emission bands in Er3+ was determined under phase transformation temperature, especially in oxygen atmosphere. Furthermore, all the fluorescence lifetimes of Er3+ also exhibited obvious extension. Our results supposed that the β‐NaYF4:Er3+ NCs have promising applications in safety ink, and the acid‐treatment by diluted hydrochloric acid is a general approach to remove deleterious organic ligands on NC surface further to weaken thermal quenching. [ABSTRACT FROM AUTHOR]

Monolithic luminescent glass‐ceramic is highly desirable for solid‐state lighting as it is stable and robust, while in practical light‐emitting devices only a thin luminescent layer is used for more efficient excitation and light extraction. In this paper, Mn2+‐doped glass and glass‐ceramic with the composition of 60SiO2‐8Na2O–20ZnO–12Ga2O3 were fabricated by the conventional melt‐quenching technique. We observe that the crystallization of α‐Zn2SiO4 nanocrystals takes place on the glass surface with controllable thickness after heat treatment. The glass samples show typical red emission peaking at λ = 620 nm that can be ascribed to the spin‐forbidden 4T1g(G) → 6A1g(S) transition of Mn2+ (d5) located in the octahedral coordination site of the glass host. After surface crystallization this red emission is retained and a new green emission at 528 nm is observed through the control of the crystallization temperature and duration, thus offering tunable emission characteristics promising for the lighting application. This change in the visible emission is interpreted in terms of the change of coordination state of Mn2+ from octahedral in a glass matrix to tetrahedral in the surface precipitated α‐Zn2SiO4 crystals. [ABSTRACT FROM AUTHOR]

In this paper, we report on spectroscopic studies of Cr3+/Ni2+ codoped transparent glass ceramics containing β-Ga2O3 nanocrystals. Energy transfer between Cr3+ and Ni2+ in the Cr3+/Ni2+ codoped glass ceramics has been investigated by steady state emission spectra, time-resolved emission spectra, and excitation spectra. The nonradiative energy transfer has been confirmed from the decrease in the Cr3+ fluorescence lifetime after Ni2+ codoping. The energy transfer efficiency is estimated and the energy transfer mechanism is discussed. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report upconversion (UC) luminescence enhancement in LaBGeO5:Yb3+, Er3+ glass‐ceramics (GCs), surface crystallized glass‐ceramics (SCGCs) and ceramics compared with the as‐melt glass fabricated by the conventional melt‐quenching technique. Based on structural investigations, we find that the nucleation and crystallization of trigonal stillwellite LaBGeO5:Yb3+, Er3+ nanocrystals occur first at the glass surface before the following volume crystallization. The local site symmetry around rare earth (RE) ions which was evaluated using the Eu3+ ions as a probe together with Judd‐Ofelt theory calculations exhibits a clear increase with the devitrification of the glass. Consequently, complete crystallization of the glass leads to largest enhancement in the UC emissions of the LaBGeO5:Yb3+, Er3+ ceramics. We ascribe the enhancement of UC luminescence in the LaBGeO5:Yb3+, Er3+ GCs, SCGCs, and ceramics to the structural ordering and the improvement of site symmetry surrounding RE ions that minimizes the rate of nonradiative relaxation process. [ABSTRACT FROM AUTHOR]

Cooperative upconversion luminescence (CUCL) occurs in spectral regions in which single ions do not have energy levels. However, all results reported so far are concentrated on luminescence properties from Yb3+ ions-doped various hosts. Here, we report the observation of nonlinear negative transmittance (NNT) at continuous-wavelength (CW) 980-nm laser diodes (LDs) pumping in silicate oxyfluoride glass ceramics (GCs)-containing CaF2:Yb3+ nanocrystals. The unique optical nonlinearity is analyzed based on energy-level transitions, dynamic evolution, rate equation, and power transmission equation, which can be explained as the cooperative optical absorption for the intense CUCL of Yb3+ ions. The NNT in the CaF2:Yb3+ nanocrystals-embedded GCs can be tailored with the power of a CW 980-nm LDs, which possesses potential for the development of future optical limiters and switches. [ABSTRACT FROM AUTHOR]

Improving upconversion luminescence efficiency of lanthanide-doped nanocrystals is always a hot topic for scientists because of its very important application in photonics, photovoltaics, biological imaging, security printing, and therapeutics. Two-color laser field has shown to be a well-established strategy to further improve the upconversion luminescence efficiency. Here, we first propose a two-color laser field combining the 850 and 980 nm lasers to improve the green and red upconversion luminescence efficiency in Er-doped NaYF nanocrystals. In this work, an important advantage for our strategy is that the population is directly pumped to the radiation energy level of the upconversion luminescence by a cooperation excitation process, but not the spontaneous decay from other higher energy levels, and so the higher luminescence enhancement efficiency can be obtained. These studies also provide a clear physical picture for the physical control mechanism of the upconversion luminescence efficiency improvement, which can pave a way to properly design the laser fields in the future study of upconversion luminescence generation and control. [ABSTRACT FROM AUTHOR]

Glass-ceramic fibers containing Cr3+-doped ZnAl2O4 nanocrystals were fabricated by the melt-in-tube method and successive heat treatment. The obtained fibers were characterized by electro-probe micro-analyzer, X-ray diffraction, Raman spectrum and high-resolution transmission electron microscopy. In our process, fibers were precursor at the drawing temperature where the fiber core glass was melted while the clad was softened. No obvious element interdiffusion between the core and the clad section or crystallization was observed in precursor fiber. After heat treatment, ZnAl2O4 nanocrystals with diameters ranging from 1.0 to 6.3 nm were precipitated in the fiber core. In comparison to precursor fiber, the glass-ceramic fiber exhibits broadband emission from Cr3+ when excited at 532 nm, making Cr3+-doped glass-ceramic fiber a promising material for broadband tunable fiber laser. Furthermore, the melt-in-tube method demonstrated here may open a new gate toward the fabrication of novel glass-ceramic fibers. [ABSTRACT FROM AUTHOR]

The construction of semiconductor nanocrystal (SNC)-based composites is of fundamental importance for various applications, including telecommunication, lasers, photovoltaics, and spintronics. The major challenges are the intentional insertion of dopants into SNCs for expanding their intrinsic functionalities and the scalable incorporation of activated SNCs into host free of hydroxyl and organic species for stabilizing and integrating their performances. An in situ approach is presented to couple the SNC doping and loading processes through self-limiting nanocrystallization of glassy phase, enabling one-step construction of fully transparent Ga2O3 SNC-glass nanocomposites. It is shown that the intentional introduction of various cation/anion impurities (e.g., F−, In3+, and Ni2+) or their combinations into Ga2O3 SNCs can be realized by taking advantage of the viscous glass matrix to enhance the desorption barrier of impurity on the SNC surface and strengthen its tendency to incorporate into the SNC lattice. The composite can be rationally activated to show wavelength-tunable and broadband luminescence covering the spectral ranges of near ultraviolet, visible, and near-infrared wavebands. The approach is predicted to be general to other SNC materials for functional modulations and will be promising for scalable fabrication of novel SNC-based composites. [ABSTRACT FROM AUTHOR]

We report on the synthesis of nanocrystalline zirconia in liquid using femtosecond laser ablation. Nanocrystalline cubic zirconia has been prepared by femtosecond laser ablation of zirconium in ammonia, while nanocrystalline tetragonal and monoclinic zirconia was synthesized in water. The physical and chemical mechanisms of the formation of nanocrystalline metastable zirconia are discussed. The intrinsic properties of femtosecond laser ablation in liquid and OH may be responsible for the synthesis of cubic zirconia. It is suggested that the femtosecond laser pulse can create higher temperature and pressure conditions at a localized area in the liquid than the nanosecond laser pulse and the cooling is also faster in the femtosecond laser ablation process, which determined the difference between the products synthesized with femtosecond and nanosecond-pulsed laser ablation. [ABSTRACT FROM AUTHOR]

Previous experimental results, using techniques associated with transmission electron microscopy (TEM), suggested that rare-earth dopants prefer the precipitated fluoride nanocrystals to the glass matrix. By contrast, this work shows that contradicting results can be obtained under different experimental conditions. In the silicate glass containing LaF3 nanocrystals, the Eu dopants distribute indistinguishably in the precipitated LaF3 and the silicate glass matrix. However, electron beam exposure during the measurement can relocate Eu, leading to the false conclusion that apparently Eu prefers the precipitated LaF3 nanoparticles to the glass matrix. Fortunately, the artefact can be avoided by shortening the exposure time. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A facile strategy based on the reaction of urea and boric acid is developed for the synthesis of toxicity-free BCNO nanocrystals containing carbon impurities and which exhibit efficient multi-color fluorescence under both single-photon and two-photon excitation. [ABSTRACT FROM AUTHOR]

We report on the conversion of near-ultraviolet radiation of 250–350 nm into near-infrared emission of 970–1100 nm in Yb3+-doped transparent glass ceramics containing Ba2TiSi2O8 nanocrystals due to the energy transfer from the silicon–oxygen-related defects to Yb3+ ions. Efficient Yb3+ emission (2F5/2→2F7/2) was detected under the excitation of defects absorption at 314 nm. The occurrence of energy transfer is proven by both steady state and time-resolved emission spectra, respectively, at 15 K. The Yb2O3 concentration dependent energy transfer efficiency has also been evaluated, and the maximum value is 65% for 8 mol % Yb2O3 doped glass ceramic. These materials are promising for the enhancement of photovoltaic conversion efficiency of silicon solar cells via spectra modification. [ABSTRACT FROM AUTHOR]

Spectral properties of Yb3+/Ni2+ codoped transparent silicate glass ceramics containing LiGa5O8 nanocrystals were investigated. The near-infrared emission intensity of Ni2+ was largely increased with Yb3+ codoping due to Yb3+→Ni2+ energy transfer. The qualitative calculation of the energy transfer constant Cs-a and rate Ps-a showed that the Yb3+→Ni2+ energy transfer was much greater than in the opposite direction. Yb3+/Ni2+ codoped glass ceramics with 0.75 mol % Yb2O3 exhibited a near-infrared emission with full width at half maximum of 290 nm and fluorescent lifetime of 920 μs. The glass ceramics are promising for broadband optical amplification. [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]

Multi-component silicate glass is an ideal matrix for fabricating glass-ceramics because of its excellent physical-chemical stability and high optical transmittance. In this paper, a series of Cr3+ doped multi-component silicate glasses were designed for the preparation of glass-ceramics that crystalizes mullite-type Cr3+:Al 4 B 2 O 9 nanocrystals. When excited at 450 nm, the obtained GCs exhibit a broadband NIR luminescence band covering a spectral region from 650 to 1200 nm. Two different crystallographic sites of Cr3+ in Al 4 B 2 O 9 nanocrystal are considered to account for the observed broadband luminescence. Due to the controllable size and uniformly dispersion of precipitated nanoparticles, this boroaluminosilicate glass-ceramic could find potential applications as monolithic near-infrared light sources in solid-state light emitting devices. [ABSTRACT FROM AUTHOR]

Biosensors working in the second near-infrared (NIR-II) spectral region have recently gained great attention owning to their deep tissue bioimaging and high spatiotemporal resolution. However, there is still a challenge to develop efficient nanothermometers based on NIR-II luminescence. Herein, we present a pioneering advancement in the field of nanothermometry by synthesizing a novel nanothermometer, a composite of fluoride nanocrystals and quantum dots. This NaYF 4 :1Nd-Ag 2 S QDs@SiO 2 nanocomposite demonstrates exceptional functionality, being excited by a single light irradiation at 808 nm for NIR-II luminescence imaging. Notably, the composite emits at two distinct wavelengths-1064 nm and 1125 nm, attributable to Nd3+ and Ag 2 S QDs, respectively. This unique emission profile enables deeper tissue penetration, mitigating overheating risks compared to conventional excitation sources at 980 nm. Furthermore, the nanomaterials exhibit remarkable temperature-sensing capabilities, with maximum sensitivities of 0.81%K−1 (S R) at 333 K. These superior sensitivities outperform many existing temperature sensors relying on thermally coupled Stark sublevels. The SiO 2 matrix not only encapsulates and protects the fluoride nanocrystals and quantum dots but also shields them from aqueous environments, ensuring outstanding luminescence stability. Our findings highlight the potential of this nanothermometer as a highly efficient temperature sensor with promising applications in cutting-edge bioapplications. This development introduces a new frontier in temperature sensing and bioimaging, showcasing its potential for transformative contributions to the field. [Display omitted] • Successful synthesis of a novel nanothermometer based on a composite comprising fluoride nanocrystals and quantum dots. • The emission intensity of Nd3+ and Ag 2 S QDs serves as a temperature sensing mechanism (0.81%K−1 (S R) at 333 K). • A versatile platform allows the integration of two different luminescent nanomaterials to meet customized requirements. • The SiO 2 matrix shields NCs and Ag 2 S QDs from water environments, ensuring excellent luminescence stability. [ABSTRACT FROM AUTHOR]

Material composition engineering and device fabrication of perovskite nanocrystals (PNCs) in solution can introduce organic contamination and entail several synthetic, processing, and stabilization steps. We report three-dimensional (3D) direct lithography of PNCs with tunable composition and bandgap in glass. The halide ion distribution was controlled at the nanoscale with ultrafast laser–induced liquid nanophase separation. The PNCs exhibit notable stability against ultraviolet irradiation, organic solution, and high temperatures (up to 250°C). Printed 3D structures in glass were used for optical storage, micro–light emitting diodes, and holographic displays. The proposed mechanisms of both PNC formation and composition tunability were verified. [ABSTRACT FROM AUTHOR]

Abstract: We fabricated lead nanocrystals inside a specially designed borosilicate glass by two parallel approaches, thermal stimulation and femtosecond laser irradiation. Thermal treatment can precipitate lead nanocrystals inside whole glass, while femtosecond laser irradiation can induce lead nanocrystals within selective area of glass. The fabricated nanocomposite exhibits large third-order optical nonlinearity and ultrafast response time, which is suitable for fabrication of ultrafast optical switches. Furthermore, the femtosecond laser induced refractive index difference between lead crystalline and glass is about 0.13, which is enough to fabricate optical devices such as photonic crystals. [Copyright &y& Elsevier]

Abstract: We report on three-dimensional precipitation of Au nanoparticles in gold ions-doped silicate glasses by a femtosecond laser irradiation and further annealing. Experimental results show that PbO addition plays the double roles of inhibiting hole-trapped centers generation and promoting formation and growth of gold nanoparticles. Additionally, glass containing PbO shows an increased non-linear absorption after femtosecond laser irradiation and annealing. The observed phenomena are significant for applications such as fabrications of three-dimensional multi-colored images inside transparent materials and three-dimensional optical memory, and integrated micro-optical switches. [Copyright &y& Elsevier]

Nanocrystals with combined properties of magnetic and fluorescence are considered as “multifunctional materials” or “smart materials” which have promising biological applications including dual-modal imaging, biological research, targeted drug delivery, clinical diagnostics and therapeutics. Utilizing a green hydrothermal method, magnetic nanocrystals Ni-doped ZnAl 2 O 4 with broadband emission at ∼1200 nm have been developed as a new type of multifunctional material. The obtained ultrasmall nanocrystals in sub-10 nm range are more easily for body clearance and less toxicity in theory. Ni ions are demonstrated distribute homogeneously in +2 valance state, which provides ferromagnetism in the diamagnetic matrix of ZnAl 2 O 4 . Under the excitation of 670 nm, the whole broad emission band centered at 1200 nm fully covers the second near-infrared window (1.1–1.4 μm). These ultrasmall Ni-doped ZnAl 2 O 4 nanocrystals with magnetic-fluorescent multifunctionality open a door to more efficient and safer biological probes. [ABSTRACT FROM AUTHOR]

Upconversion luminescence of lanthanide ion doped nanocrystals under ultrashort laser pulse excitation can find significant applications in areas like super-resolution nonlinear microscopic imaging and attracts increasing attention. Though major excitation mechanisms, such as excited state absorption (ESA), energy transfer upconversion (ETU) and multi-photon absorption (MPA), have been analyzed and discussed intensively, quantitative differentiation of their respective contributions with convincing experimental proof has seldom been reported however. Here we report experimental demonstration of a simple but effective way to quantitatively identify simultaneous MPA from other mechanisms like ESA and ETU involved in the Er3+ doped NaYF 4 nanocrystals in aluminosilicate glass ceramics under femtosecond laser field excitation. Comparative studies using laser pulses of the same spectral bandwidth but different time duration or repetition rate are performed and convincing experimental evidences for their respective contribution weights are obtained. The dependence of the MPA excitation efficiency on the spectral bandwidth of the femtosecond laser pulse is also explored for maximizing the upconversion luminescence yield. And predictions from a theoretical model agree well with experimental observations. • Demonstrating an effective way to identify multi-photon absorption (MPA) from other mechanisms, like ESA or ETU. • The MPA is found to play a dominant role in exciting the green upconversion emission. • The MPA excitation efficiency can be maximized by optimizing the spectral bandwidth of the femtosecond laser. [ABSTRACT FROM AUTHOR]

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]

Abstract: Transparent glasses imbedded with functional nanocrystals have attracted considerable interest and been studied widely in the past several decades, due to their applications in optical devices, such as optical amplifiers, nonlinear optical devices, optical storage, 3D displays, etc. Femtosecond (fs) laser irradiation induced crystallization of glass has been proved to be a powerful tool to realize the space-selective precipitation of various nanocrystals inside glasses. In this review, we highlight our recent research achievements on the fs laser induced precipitation of nanocrystals inside glasses, including nonlinear optical crystal, upconversion luminescence crystal, high refractive index crystal, and metal nanoparticles. These studies not only help to understand the interaction process between fs laser and glassy materials, but also have potential applications in the fabrication of micro-optical devices. [Copyright &y& Elsevier]

Highlights: [•] Mono-dispersed ZnS: Mn nanocrystals were synthesized by a hydrothermal route. [•] Photoluminescence of nanocrystals were studied by steady and transient state spectra. [•] A novel energy transfer mechanism of ZnS: Mn nanocrystals was proposed. [ABSTRACT FROM AUTHOR]

Abstract: We report on the precipitation of Si nanocrystals inside a borosilicate glass by using an 800nm, 250kHz femtosecond laser irradiation, which was confirmed with X-ray diffraction, Raman spectra and transmission electron microscopy analyses. Refractive index profile reveals that the refractive index of the Si nanocrystals precipitated region increased up to 8.7% in comparison with that of the unirradiated area, leading to a large diffraction efficiency of the fabricated dot structure. Furthermore, the third-order optical nonlinearity of the Si nanocrystals precipitated glass is greatly enhanced based on the Z-scan measurement. These results may find applications for the fabrication diffractive optical devices and optical switches. [Copyright &y& Elsevier]

Abstract: With the irradiation by femtosecond (fs) laser with high repetition rate, GeS2 micro/nano-crystalline formation and microstructural modification occurred in pseudo-binary GeS2–In2S3 glass, while almost no similar change was observed in GeS2 glass. The addition of In2S3 is beneficial for the precipitation of GeS2 micro/nano-crystals. It is expected that functional micro/nano-crystals can be controllably prepared in chalcogenide glasses by fs laser irradiation through glass composition design. [Copyright &y& Elsevier]

Abstract: Tm3+–Yb3+ co-doped transparent oxyfluoride glass ceramics were prepared through thermal treatment of the as-prepared glasses. The precipitation of nanocrystals and the incorporation of Tm3+ and Yb3+ into the nanocrystals were confirmed by X-ray diffraction and absorption spectra. Based on the Judd–Ofelt theory, the J–O parameters Ω λ (λ =2, 4, 6), spontaneous radiative transition rates, radiative lifetimes and fluorescence branching ratios of Tm3+ in both as-prepared glasses and glass ceramics were calculated. Intense mid-IR emission and upconversion luminescence in the Tm3+ and Yb3+ co-doped glass ceramics were observed under 980nm excitation. Especially, compared with that of the as-prepared glasses, mid-IR luminescence intensity of Tm3+ in the glass ceramics was greatly enhanced. Desirable spectroscopic characteristics suggest that these oxyfluoride glass ceramics may be promising mid-IR laser active medium. [ABSTRACT FROM AUTHOR]

Abstract: Photoluminescence properties of Sm3+, Dy3+, and Tm3+-doped transparent oxyfluoride silicate glass ceramics containing CaF2 nanocrystals were reported. Emission bands of 4G5/2 → 6H5/2 (562nm), 4G5/2 → 6H7/2 (598nm), 4G5/2 → 6H9/2 (645nm) and 4G5/2 → 6H11/2 (706nm) for the Sm3+: glass and glass ceramic, with an excitation at 6H5/2 → 4F7/2 (402nm) have been recorded. Of them, 4G5/2 → 6H7/2 (598nm) has shown a bright orange emission. With regard to the Dy3+: glass, a bright fluorescent yellow emission at 575nm (4F9/2 → 6H13/2) and blue emission at 481nm (4F9/2 → 6H15/2) have been observed, apart from 662nm (4F9/2 → 6H11/2) emission transition with an excitation at 386nm (6H15/2 → 4I13/2 + 4F7/2) wavelength. Emission bands of 1G4 → 3F4 (650nm) and 1G4 → 3H5 (795nm) transitions for the Tm3+: glass and glass ceramic, with an excitation at 3H6 → 1G4 (467nm) have been observed. Of them, 1G4 → 3F4 (650nm) has shown bright red emission. Decay lifetime measurements were also carried out for all the observed Sm3+, Dy3+, and Tm3+-doped glass and glass ceramic emission bands. [Copyright &y& Elsevier]

Abstract: We report on highly efficient broadband near-infrared photoluminescence (PL) in Ni2+-doped glass ceramics (GCs) films fabricated by annealing Si/Ni2+-doped glass superlattices (SNGS). Over two orders of magnitude enhancement of PL can be achieved in comparison with that from the annealed glass film. The PL lifetime of the annealed SNGS is several milliseconds, which is much longer than those of bulk GCs. The strong PL enhancement results from the formation of high-quality cordierite nanocrystals because the Si layers act as Si source for the crystal growth. This technique can be extended to fabricate other types of high-quality GCs films. [Copyright &y& Elsevier]

Abstract: We obtain Au and Ag nanoparticles precipitated in glasses by irradiation of focused femtosecond pulses, and investigate the nonlinear absorptions of the glasses by using Z-scan technique with ns pulses at 532nm. We observe the saturable absorption behavior for Au nanoparticles precipitated glasses and the reverse saturable ones for Ag ones. We also obtain, by fitting to the experimental results in the light of the local field effect near and away from the surface plasmon resonance, and 5.9×10−8 esu for the imaginary parts of the third-order susceptibilities for Au and Ag nanoparticles, respectively. The nonlinear response of Au nanoparticles in the glass samples arises mainly from the hot-electron contribution and the saturation of the interband transitions near the surface plasmon resonance, whereas that of Ag nanoparticles in the glass samples from the interband transitions. These show that the obtained glasses can be used as optoelectronic devices suiting for different demands. [Copyright &y& Elsevier]