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Tunable Chromaticity and High Color Rendering Index of WLEDs with CaAlSiN <sub/>3</sub> :Eu <sup>2+</sup> and YAG:Ce <sup>3+</sup> Dual Phosphora??ina??silicaa??glass
摘要： Phosphors-in-glass (PiG), which serves as a potential bi-replacement of both phosphors and organic encapsulants in high-power white light-emitting diodes (WLEDs), has captured much attention due to its high thermal stability and excellent luminescent properties. However, due to the high temperature-sensitivity and the chemical reactions between phosphors with glass matrix, a variety of phosphors, especially red phosphors could be hardly dispersed into the glass without thermal quenching and decomposition, which greatly limits the improvement of color rendering index and chromaticity tunability of the WLEDs. In this study, adopting the mesoporous silica (FDU-12) and commercial phosphors as raw materials, the phosphors-in-silica-glasses (PiSGs) embedded with red phosphor CaAlSiN3:Eu2+ and yellow phosphor YAG:Ce3+ have been successfully prepared at low sintering temperature (950 ?C) and short preparation time (10 min) using spark plasma sintering. Owing to the well preservation of the originally emissive properties of the embedded phosphors, the warm WLEDs with tunable chromaticity and exhibited a superior performance with LE of 133 lm/W, CCT of 3970 K and CRI of 81 were fabricated by encapsulating the as-prepared PiSGs on the blue chips. Moreover, the PiSG composite exhibits a high thermal conductivity up to 1.6 W/m·K.
关键词： white light-emitting diodes,phosphor in silica glass,tunable chromaticity,mesoporous silica
更新于2025-09-23 15:21:01
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Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica
摘要： A novel nanocomposite luminescent material was prepared by taking advantage of the versatile wet impregnation method for the dispersion of CdTe quantum dots (QDs) into mesoporous silica host matrix and thus providing great interaction between oxygen and QDs, with potential application in an optical oxygen sensor. The optical/spectroscopic properties of the QDs suspended in aqueous media and incorporated in mesoporous silica were evaluated as a function of aging time, temperature variation and oxygen concentration. Luminescence quenching studies were carried out for both QDs suspended in solution and loaded into the silica matrix, in the presence of varying O2 concentration. By Stern-Volmer plot analysis, obtained at different temperatures, it was possible to verify the existence of two types of emission quenching mechanisms for CdTe QDs. After aging for 120 days at room temperature, the QDs in colloidal suspension displayed a small red-shifted emission, which was interpreted as a decreased bandgap energy owing to the increase in the nanocrystal size. In contrast, the emission spectrum of CdTe QDs loaded into the mesoporous SiO2 matrix remained unchanged after aging for the same time at ambient temperature. The presented results will contribute to the discernment of oxygen quenching mechanisms and chemical stability of optical sensors based on CdTe QDs.
关键词： oxygen sensors,mesoporous silica,Quantum Dots,CdTe,wet impregnation,fluorescence quenching
更新于2025-09-23 15:21:01
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Self-focusing of UV radiation in 1 mm scale plasma in a deep ablative crater produced by 100 ns, 1 GW KrF laser pulse in the context of ICF
摘要： Experiments at the GARPUN KrF laser facility and 2D simulations using the NUTCY code were performed to study the irradiation of metal and polymethyl methacrylate (PMMA) targets by 100 ns UV pulses at intensities up to 5 3 1012 W cm?2. In both targets, a deep crater of length 1 mm was produced owing to the 2D geometry of the supersonic propagation of the ablation front in condensed matter that was pushed sideways by a conical shock wave. Small-scale ?lamentation of the laser beam caused by thermal self-focusing of radiation in the crater-con?ned plasma was evidenced by the presence of a microcrater relief on the bottom of the main crater. In translucent PMMA, with a penetration depth for UV light of several hundred micrometers, a long narrow channel of length 1 mm and diameter 30 μm was observed emerging from the crater vertex. Similar channels with a length-to-diameter aspect ratio of ～1000 were produced by a repeated-pulse KrF laser in PMMA and fused silica glass at an intensity of ～109 W cm?2. This channel formation is attributed to the effects of radiation self-focusing in the plasma and Kerr self-focusing in a partially transparent target material after shallow-angle re?ection by the crater wall. Experimental modeling of the initial stage of inertial con?nement fusion-scale direct-drive KrF laser interaction with subcritical coronal plasmas from spherical and cone-type targets using crater-con?ned plasmas seems to be feasible with increased laser intensity above 1014 W cm?2.
关键词： fused silica glass,UV radiation,PMMA,KrF laser,plasma,ICF,self-focusing
更新于2025-09-23 15:21:01
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Application of laser backscattering imaging for the physico-chemical characterisation of antimicrobial silica particles functionalised with plant essential oils
摘要： The capacity of orthogonal imaging applied to laser-backscattering for characterising antimicrobial particles based on immobilised essential oils was tested. Different particles were synthesised using various particle and oils. Samples were characterised physico-chemically and by an imaging technique. The technique recorded the generated patterns because of the laser-particles interaction during the sedimentation process. The series of images were transformed into an orthogonal image. Data extraction varied depending on the fragmentation degree of image length. After the multivariate analysis, the physico-chemical results showed variability due to particle size. That variability diminished the effect of oils for large sizes. The imaging data collected these properties, which could be used to recognise both particle size and oil type. Thus the prediction of the properties was successful. The position in the physico-chemical space of variance was also predicted. Hence this technique could complement a low-cost method to evaluate the properties of functionalised particles with oils.
关键词： Essential oils,Silica particles,Laser backscattering,Orthogonal imaging,Physico-chemical characterisation
更新于2025-09-23 15:21:01
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Highly Efficient and Stable CsPbBr3 Perovskite Quantum Dots by Encapsulating in Dual-Shell Hollow Silica Spheres for WLEDs
摘要： Poor stability of CsPbX3 (X = Cl, Br or I) perovskite quantum dots (QDs) has greatly hindered their practical photoelectric applications, and how to improve it still remains a critical challenge. Herein, we encapsulated the CsPbBr3 QDs into a dual-shell hollow silica (SiO2) spheres via a simple successive ionic layer adsorption and reaction (SILAR) method. The hierarchical dual-shell structures permit CsPbBr3 QDs to be anchored on the interior of the SiO2 spheres while keeping the outside surface undisturbed, which can protect CsPbBr3 QDs from direct exposure to the atmosphere. Due to the comprehensive protection of dual-shell hollow SiO2 spheres, the CsPbBr3/SiO2 nanospheres exhibit markedly enhanced stability against light and heat, with residual PL intensity of 89% after continuous exposure of 72 h to UV light and 65% at 100?C heat treatment, respectively. In addition, an optimal PLQY of 89% is obtained with suppressed nonradiative recombination. Finally, the fabricated white light-emitting diodes (LEDs) device by employing CsPbBr3/SiO2 green phosphors could achieve a wide color gamut covering up to 136% of the NTSC standard. This work provides a novel SiO2-based encapsulation approach to solve the intrinsic instability issues of CsPbBr3 QDs, which has a profound impact on their practical applications.
关键词： photoluminescence quantum yield,CsPbBr3 quantum dots,dual-shell hollow silica spheres,stability,white light-emitting diodes
更新于2025-09-23 15:21:01
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Polymer-Silica Hybrid On-Chip Amplifier with Vertical Pumping Method
摘要： This article demonstrates a multilayer polymer-silica hybrid on-chip amplifier combining mode division multiplexing method. The multilayer amplifier consists of a pumping silica waveguide and an amplifying polymer waveguide. The pumping waveguide possesses the stability and the high damage threshold. The amplifying waveguide takes the advantages of the high compatibility and the high doping rate. The vertical pump of mode division multiplexing method can introduce the pumping light into the amplifying waveguide at any desired position of the chip. By the isolation method between signal and pumping light, the pumping light can be coupled into the amplifying waveguide, while the signal light cannot be coupled into the pumping waveguide. The parameters of doping rates, waveguide lengths, overlap factors, coupling parameters are calculated to optimize the gain characteristics of the amplifier. The amplifier with three position-optimized pumping light was designed achieving a maximum gain of 33.89 dB/cm with a waveguide length of 6 cm, a signal power of 0.1 mW and a pumping power of 300 mW. This polymer-silica hybrid amplifier is promising for the on-chip loss compensation of the 3D photonic integrated circuits and all optical transistors.
关键词： vertical pumping method,on-chip amplifier,polymer-silica hybrid,mode division multiplexing,3D photonic integrated circuits
更新于2025-09-23 15:21:01
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Morphology study and threshold measurement of laser induced damage of nano-porous antireflective silica thin films in nano- and femtosecond pulse regimes
摘要： Laser induced damage threshold (LIDT) of nano-porous antire?ective silica thin ?lms is measured using 10 ns laser pulses at k = 532 nm. The thin ?lms are prepared by dip-coating of BK7 substrates and then drying them by three different heating methods, to see how their LIDT and transmission are affected. Furthermore, using SEM imaging, the morphology of the laser induced damages is inspected and compared to those of similar samples, previously irradiated by femtosecond laser pulses at k = 800 nm. The images evidently show that in the regions damaged by nanosecond pulses, the silica nanoparticles are melted and fused to each other, while in the samples irradiated by femtosecond pulses, the silica nanoparticles are sputtered and dispersed around, in the damaged area. The SEM images clearly demonstrate the different damage mechanisms involved in the nanosecond and femtosecond regimes of interaction.
关键词： Optical thin ?lms,Silica thin ?lms,Nano-porous thin ?lms,Laser damage
更新于2025-09-23 15:21:01
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Dielectric and electro-optic studies of a ferroelectric liquid crystal dispersed with different sizes of silica nanoparticles
摘要： The impact of the size of silica nanoparticles (SNPs) on the properties of ferroelectric liquid crystals (KCFLC 10R) has been investigated by electro-optical and dielectric techniques. We have found that the doping of silica nanoparticles in the host ferroelectric liquid crystal strongly affects the various properties of doped systems. Doping of silica nanoparticles shows a small decrease in spontaneous polarisation and faster switching time. An improvement in permittivity and conductivity with the temperature at a constant frequency was also noticed after dispersion. This dependence is stronger for large size particles (,40 nm) and weaker for small size particles (~12 nm). The Goldstone mode (GM) shifts towards the higher relaxation frequency. These results would be useful to manufacture better optical and electronic devices for display, switching and beam steering applications.
关键词： relaxation frequency,Ferroelectric liquid crystals,spontaneous polarisation,silica nanoparticles,goldstone mode,electro-optical,switching time
更新于2025-09-23 15:21:01
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Bare Silica Opals for Real-Time Humidity Sensing
摘要： The photonic properties of 3D colloidal crystals made of St?ber silica spheres are shown to significantly depend on the relative humidity of the environment. The photonic bandgap of bare artificial opals formed by hydrophilic silica markedly varies in humid air along the entire range of water vapor concentration without the need for infiltration of functionalization. The optical changes are highly sensitive to humidity variation (especially in low-humidity range) and very fast response times of 60 ms, mainly ascribed to the absence of intermediate processes, the favorable bandgap characteristics (high intensity and sharp edges) and the high air accessibility to the open opal voids. Contrary to common approaches for photonic crystal sensors—seeking visual detection via large spectral shifts but having important shortcomings,—it is demonstrated that the well-defined photonic bandgap of bare silica opals allows, even for moderate shifts, outstanding sensing performance by proper monitoring with inexpensive equipment (no spectroscopic detection is needed). As a result, the rapid and reproducible photonic response enables accurate, real-time retrieval of the ambient humidity. The economical, one-step fabrication, and the efficient performance make silica artificial opals suitable for a new type of precise, low-cost, and real-time humidity sensors.
关键词： water vapor adsorption/desorption,real-time sensing,humidity sensors,artificial silica opals,photonic colloidal crystals
更新于2025-09-23 15:21:01
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Confined whispering-gallery mode in silica double-toroid microcavities for optical sensing and trapping
摘要： We propose and theoretically study a silica double-toroid microcavity to confine the whispering-gallery mode (WGM) in an ultra-small space, which consists of two toroid-to-toroid coupled cavities separated by a nanoscale gap region with low refractive index, such as the air gap. Benefitting from the strong field localization of the “slot” effect, power enhancement of symmetric WGMs in the gap results in the ultra-small mode volume of 4.8 μm3, which is quite smaller than the conventional toroidal microcavity with mode volume of about hundreds of cubic micrometers. The confined modes hold the potential advantages over conventional photonic devices, especially in the applications of the sensing and optical trapping. In the application of refractometer, a high refractive index sensitivity of up to 468 nm per refractive index unit (nm/RIU) can be obtained in the 1000 nm wavelength band. In the optical trapping application, the double-toroid microcavity enables a significant field enhancement in the confined WGM, and the gradient force could reach as high as 22 pN/W for a single nanoparticle with the radius of 5 nm. As the potential advantages, this study of silica double-toroid microcavity provides a good reference for realizing the high-efficient photonic applications such as optical sensing and trapping.
关键词： optical sensing,refractometer,silica double-toroid microcavity,gradient force,optical trapping,whispering-gallery mode
更新于2025-09-23 15:21:01