- 标题
- 摘要
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- 实验方案
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Realization of sharp visible WGM lasing from Sm<sup>3+</sup>:ZnO micro-spheres fabricated by laser ablation technique
摘要： In this paper, the whispering gallery mode lasing from Sm3+ doped ZnO micro-spheres operating in the visible wavelength range 550-750 nm is studied. Highly smooth and crystalline Sm3+:ZnO micro-spheres of various diameters were synthesized by simple laser ablation of sintered target in air. The dopant concentration has been restricted within the solid solubility limit of 1 mol%. The Sm3+ ion substitution in ZnO matrix results in the formation of inter-band levels by the characteristic 4f level of Sm3+ in the forbidden gap of ZnO. Thus, when the micro-spheres are excited with 488 nm, four major visible emissions associated with Sm3+ f ? f transitions namely, transitions from 4G5/2 to its low-lying multiplets of 6HJ (J = 5/2, 7/2, 9/2 and 11/2), are obtained. These emissions are coupled to the WGMs of the Sm3+:ZnO micro-cavity resulting in sharp resonances in the visible region. Interestingly, the resonances are found to be lasing above lower pumping powers. The Q-factor obtained is of the order of 103 for spheres of size ranging 1.8-10.2 μm. The best Q-factor obtained is 3744 for 561.61 nm peak (FWHM 0.15 nm) from 8 μm sphere. These results would ?nd a place in visible range lasing and sensor applications.
关键词： Q-factor.,visible renge,cavity resonator,WGM resonances,lasing,Microsphere
更新于2025-09-11 14:15:04
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Optimal Sphere-Sensor Ratio for Microsphere-Enhanced Photodetector Sensors in Cameras/Telescopes with and without Central Obscuration
摘要： A microsphere lens on top of a photodetector sensor increases its sensitivity and reduces its Noise-to-Signal Ratio (NSR), as shown in our previous work. This paper discusses a methodology to determine the optimal sphere-sensor ratio, in terms of increased current sensitivity, for microsphere-lens-enhanced photodetectors, using computational analysis including a modeling, with an experimentally derived photo-detector sensor responsivity and simulation setup that emulates conditions generally found within cameras and telescopes. In particular, we study and analyze the effect that several variables have on such ratios. We focus on variables such as microsphere material type, photodetector type, light source temperature, and in the case of reflective telescopes, central obscurations from a secondary mirror. Results of the effect of microsphere-sensor misalignment on such ratios are also presented. As we show in this paper, since the optimized ratio is dependent on a given wavenumber considered, therefore the proposed methodology uses an integral optimization over a given spectral band to derive the optimized ratio over that band. Some of our findings show, for the first time, that the optimal ratio is virtually independent of a given central obscuration. Finally, we demonstrate here the flexibility of the proposed methodology in showing performances of microsphere-enhanced photodetector sensors.
关键词： central obscuration,computational analysis,current sensitivity,photodetector sensor,optimal sphere-sensor ratio,microsphere lens
更新于2025-09-11 14:15:04
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Preparation of high-porosity Al2O3 ceramic foams via selective laser sintering of Al2O3 poly-hollow microspheres
摘要： In this paper, high-porosity Al2O3 ceramic foams called Al2O3 PHM ceramics were fabricated through selective laser sintering (SLS) via Al2O3 poly-hollow microspheres (Al2O3 PHMs). SLS parameters were optimized by an orthogonal experiment as laser power = 6 W, scanning speed = 1800 mm/s, and scanning space = 0.15 mm. The effect of sintering temperature on microstructure, shrinkage, porosity, phase composition, mechanical properties and pore size distribution of Al2O3 PHM ceramics were investigated. When sintering temperature increased, Al2O3 PHM ceramics contained only Al2O3 phase and were gradually densified. With the raise of sintering temperature, the porosity of Al2O3 PHM ceramics decreased gradually from 77.09% to 72.41%, but shrinkage in H direction and compressive strength of Al2O3 PHM ceramics increased from 6.63% and 0.18 MPa to 13.10% and 0.72 MPa, respectively. Sintering temperature had little effect on pore size distribution of Al2O3 PHM ceramics, which only declined from 24.2 to 21.4 μm with the increase of sintering temperature from 1600 to 1650 °C. This method can not only directly prepare ceramic foams with complex shapes, but also control properties of ceramic foams. It provides a simple preparation method for many kinds of ceramic foams with complex structure and high porosity by using PHMs with different composition.
关键词： Selective laser sintering,Porosity,Poly-hollow microsphere,Ceramic foams,Mechanical properties
更新于2025-09-11 14:15:04
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Controllable preparation and high properties of fluorescence and surface enhanced raman spectra encoded poly(glycidyl methacrylate) microsphere
摘要： Novel fluorescence and SERS encoded microspheres based on poly(glycidyl methacrylate) (PGMA) microspheres were developed by a controllable approach. The microspheres were encoded by four fluorescence dyes and three surface enhanced Raman spectra (SERS) probes. Multiple dyes could be simultaneously incorporated into the PGMA microspheres for encoding and the intensity of the fluorescence can be tuned by adjusting the feeding ratio. The PGMA microspheres were coated by silver nanoparticles and encoded by single and multiple SERS reporters. The fluorescence and SERS joint encoded PGMA microspheres were fabricated. All the fluorescence encoding signals can be excited at 488 nm. The fluorescent and SERS signals of dual-mode microspheres could be obtained from two optical channels and non-overlapping of emission spectra was observed in these encoded microspheres, which greatly increased the encoding capacity. The as prepared fluorescence and SERS encoded microspheres possess stable and distinct spectral encoding signals, large encoding capacity.
关键词： polymer microsphere,spectra encoding,polymer composites
更新于2025-09-10 09:29:36
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Synthesis of silica microspheres on silicon-modified carbon foams under ablation
摘要： Silica microspheres (SMs) were in situ synthesized in silicon-modified porous carbon foams (SCFs) by an economic and efficient technique – high temperature oxyacetylene torch ablation. The microstructure and formation mechanism of SMs were analyzed in detail. Results showed that the resultant SMs generally were several microns in diameter, and mainly distributed in the ablation center zone. The formation mechanism was governed by the vapor–liquid–solid principle during the process of ablation and cooling. The influence of the ablative flame on the physicochemical property of SCFs was the leading cause of the bizarre SMs.
关键词： ablation,Silica microsphere,carbon foam
更新于2025-09-09 09:28:46
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Photoactivity of Ag/TiO2 Microsphere by One-Step Hydrothermal Method
摘要： Ag/TiO2 microsphere photocatalyst was prepared via one step hydrothermal method and prepared catalyst was used for photodegradation of rhodamine B under visible light. The Ag/TiO2 catalyst was characterized through X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed Ag was uniformly distributed in the titanium matrix. The 6 % Ag doped TiO2 catalyst had the higher photoactivity than other proportion to degrade rhodamine B 86.6 % within 60 min under visible light. The Ag doped TiO2 also had the good activity under solar light cut off UV light.
关键词： Ag doped TiO2,Photodegradation,Hydrothermal method,Microsphere
更新于2025-09-09 09:28:46
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[IEEE NAECON 2018 - IEEE National Aerospace and Electronics Conference - Dayton, OH, USA (2018.7.23-2018.7.26)] NAECON 2018 - IEEE National Aerospace and Electronics Conference - The Art of the Impossible: Sorting Dielectric Microspheres by using Light
摘要： Use of resonant light forces opens up a unique approach to high-volume sorting of microspherical resonators with 1/Q accuracy, where Q is the resonance quality factor. Based on a two-dimensional model, it is shown that the sorting can be realized by allowing spherical particles to traverse a focused beam. Under resonance with the whispering gallery modes (WGM), the particles acquire significant velocity along the laser beam which should allow sorting dielectric microspheres with almost identical positions of their WGM resonances. This is an enabling technology for developing super-low-loss coupled-cavity structures and devices.
关键词： optical coupling,optical force,microsphere,whispering gallery mode,photonic molecule
更新于2025-09-09 09:28:46
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Pd/TiO2 @ Carbon Microspheres Derived from Chitin for Highly Efficient Photocatalytic Degradation of Volatile Organic Compounds
摘要： Facing the serious air pollution caused by the volatile organic compounds (VOCs), the highly efficient degradation and removal of VOCs have attracted great attentions. To develop efficient novel photocatalysts, Pd/TiO2 @ carbon nanofibrous microspheres were constructed by carbonizing the TiO2/chitin microspheres, followed by immobilizing Pd nanoparticles on the TiO2/carbon microspheres via a green pathway. The composite microspheres were composed of carbon nanofibers, on which TiO2 nanoparticles and ultra-small Pd nanoparticles with mean size of 1 nm were well immobilized and distributed, supported by transmission electron microscope and elemental mappings results. The Pd/TiO2 @ carbon microspheres were used for the gas phase photodegradation of VOCs. The results demonstrated that the conversion of toluene and benzene to CO2 and H2O reached 96.4% and 91.7%, respectively, which were higher than the reported values in the literatures. The combination of TiO2 and Pd nanoparticles played an important role on the enhancement of the catalytic activity. Moreover, the Pd/TiO2 @ carbon microspheres could be recycled and reused. This work provided a new strategy to eliminate VOCs, which was beneficial to a sustainable world.
关键词： catalyst TiO2 nanoparticles,Chitin microsphere,Pd nanoparticles,degradation of volatile organic compounds,carbon nanofibers
更新于2025-09-04 15:30:14
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Colorimetric Sensor Array for Monitoring CO and Ethylene
摘要： Developing miniaturized and inexpensive detectors remains an important and practical goal for field-deployable monitoring of toxic gases and other bioactive volatiles. CO (a common toxic pollutant) and ethylene (the phytohormone primarily responsible for fruit ripening) share the capability of strong back-π-bonding to low-oxidation-state metal ions, which has proved important in the development of metal-ion-based sensors for these gases. We report herein cumulative colorimetric sensor arrays based on Pd(II)-silica porous microsphere sensors and their application as an optoelectronic nose for rapid colorimetric quantification of airborne CO and ethylene. Quantitative analysis of two gases was obtained in the range of 0.5 to 50 ppm with detection limits at the sub-parts-per-million level (～0.4 ppm) after 2 min of exposure and ～0.2 ppm after 20 min (i.e., <0.5% of the permissible exposure limit for CO and <10% of the ethylene concentration needed for fruit ripening). We further validate that common potential interfering agents (e.g., changes in humidity or other similar air pollutants such as NOx, SO2, H2S, or acetylene) are not misidentified with CO or ethylene. Finally, the sensor is successfully used for the quantification of ethylene emitted from ripening bananas, demonstrating its potential applications in the monitoring of fruit ripening during storage.
关键词： Pd(II)-silica porous microsphere sensors,CO,ethylene,colorimetric sensor array,optoelectronic nose
更新于2025-09-04 15:30:14