最新刊期
卷 39 ， 期 5 ， 2018
- 摘要：Photoluminescence(PL) properties of Mn doped CsPbCl3 (Mn:CsPbCl3) perovskite quantum dots(QDs) with various Mn/Pb molar ratios were studied. Two emission bands peaked at around 400 nm and 600 nm, respectively, were observed in Mn:CsPbCl3 QDs at room temperature. The PL intensity of Mn ion emission in the Mn:CsPbCl3 QDs was significantly enhanced with respect to the band edge exciton emission as Mn/Pb molar ratio increased from 0.5:1 to 5:1. Both the exciton absorption and emission bands in the doped QDs shifted to the blue, which was consistent with the reduction of the QD size. The red shift of Mn2+ emission band with increasing the molar ratio was considered to result from the formation of Mn2+-Mn2+ pairs in the doped QDs due to high concentration Mn doping. Further, the PL quantum efficiency of Mn:CsPbCl3 QDs as a function of Mn/Pb molar ratio was studied in detail. It is found that the PL quantum yield of Mn2+ gradually increases with the increasing of Mn/Pb molar ratio. The maximum PL quantum yield reaches 62% as Mn/Pb molar ratio is 2:1. The PL quantum yield drops continually with the increasing of Mn/Pb molar ratio to 5:1. The reduction of PL quantum yield at high concentration Mn doping is related to Mn doping concentration-induced PL quenching due to the formation of Mn2+-Mn2+ pairs. The temperature-dependence of PL spectra in Mn:CsPbCl3 QDs demonstrates that Mn2+ emission band shifts to the blue and the emission width is broadened, while PL intensity increases, which is in contrast to Ⅱ-Ⅵ semiconductor QDs.关键词：perovskite;doped quantum dots;photoluminescence;quantum yield318|163|10更新时间：2020-08-12
- 摘要：KHo0.04Tm0.06Yb0.9(WO4)2 laser crystal was grown by the top seeded solution growth (TSSG) method. The absorption and fluorescent spectra of the crystal were measured, and the spectral parameters were calculated, too. The experimental results show that there is a broader absorption band at the range of 890-1 000 nm with a full width at half maximum (FWHM) of 90 nm. The absorption cross section of main emission peak at 1 000 nm is 16.92×10-20 cm2. Meanwhile, Tm3+ ions in the crystal have a wider absorption band at 1 690-1 812 nm with a FWHM of 118 nm. Therefore, the energy transfer of Yb→Ho, Yb→Tm, Tm→Ho can be easily achieved. The spectral strength parameters of the crystal were calculated based on the Judd-Ofelt theory. According to the energy level diagram of Tm3+, Ho3+ and Yb3+ ions, three kinds of energy transfer modes at 1 750-2 200 nm emission were discussed. The stimulated emission cross section of main emission peak at 2 030 nm is 3.47×10-20 cm2, which indicates that the crystal can be used as an excellent laser gain medium at the range of 2 μm.关键词：laser crystal;absorption spectrum;fluorescent spectrum;spectral parameter calculation114|177|0更新时间：2020-08-12
- 摘要：A simple fluorescent probe HM based on acylhydrazone structure was synthesized for recognition of zinc ion (Zn2+). The recognition process of Zn2+ was studied by ESI-MS, fluorescence spectroscopy and UV-Vis spectroscopy. UV-Vis titration test shows that the addition of Zn2+ into HM aqueous solution caused gradually drop of the absorption peak at 386 nm. At the same time, a new absorption peak at 420 nm appeared and the intensity gradually increased until equilibrium. A sharp isosbestic point at 396 nm was obtained. Florescence spectroscopy indicates that the fluorescent probe HM exhibites high selectivity for detection of Zn2+. The fluorescence intensity was increased by 2.5 times at excited wavelength of 510 nm. The lowest detection limit of HM for Zn2+ is up to 1.0×10-5 mol/L and the fluorescence quantum yield is 0.02. The recognition process is presumed to be caused by PET (photoinduced electron transfer) process combining with CHEF (Chelation enhanced fluorescence) mechanism. The Job's plot and ESI-MS results demonstrate a 1:1 stoichiometric host-guest complex for probe molecular HM and Zn2+, with the association constant being calculated as K=4.05×106L·mol-1.关键词：zinc ion;fluorescence probe;acylhydrazone;recognition104|288|3更新时间：2020-08-12
- 摘要：Perovskite quantum dots(PeQDs) are showing commercial promise for achieving wide color gamut in LCD displays for their tunable spectrum, high efficiency and much narrower FWHM emission spectrum than that of phosphors. We report a method to produce white light emitting LEDs (wLEDs) used for wide color gamut backlight using green light emitting CsPb(Br0.75I0.25)3 (CPBI) inorganic PeQDs and red light emitting K2SiF6:Mn4+ (KSF) phosphor powder as color conversion materials. CPBI PeQDs with emission peak wavelength of 526 nm and FWHM of 27 nm were successfully synthesized. The color points of the blue LED, the CsPb(Br0.75I0.25)3 PeQDs and the KSF powder in the CIE 1931 color space yield a wide color gamut covering 107% of the NTSC standard. PeQDs, KSF and PeQDs-KSF conversion films were fabricated by screen printing and UV curing processes. Three kinds of wLEDs with different package structure were produced using blue LED chip and conversion films. Lighting properties of these devices were discussed and the sample with KSF film on the surface showed the optimum lumen efficiency of 102 lm/W and color temperature of 7 100 K.关键词：perovskite quantum dots;CsPb(Br0.75I0.25)3;KSF;wide color gamut169|326|9更新时间：2020-08-12
- 摘要：Using 2-(phenylsulfonyl) acetophenone derivatives as the ancillary ligands, and 2-phenylpyridine derivatives as the main ligands, six iridium complexes (1:(dfppy)2Ir(PSAP), 2:(tfmppy)2Ir(PSAP), 3:(ftfmppy)2Ir(PSAP), 4:(dfppy)2Ir(TSAP), 5:(tfmppy)2Ir(TSAP), 6:(ftfmppy)2Ir(TSAP)) were synthesized, respectively. The complexes show phosphorescence emission maxima from 450 nm to 502 nm in CH2Cl2 solution with the quantum efficiencies from 13.2% to 51.1%, respectively. All the complexes exhibit emissions peaked from 482 nm to 503 nm in solid state, respectively. By using these complexes solid powder as emitters, the light emitting diodes with the blue GaN material as substrate were prepared. The CIE color coordinates are in blue-green and yellow-green regions for the LED based on all the complexes. The maximum light emitting efficiency value for (ftfmppy)2Ir(TSAP) based LED is 5.6 lm·W-1, and the color of (dfppy)2Ir(PSAP) based LED (0.316, 0.431) is almost near-white.关键词：2-(phenylsulfonyl) acetophenone;iridium complexes;phosphorescent materials;photoluminescence123|166|1更新时间：2020-08-12
- 摘要：Ca0.8Zn0.2TiO3:0.2%Pr3+,Si4+ and Ca0.8Zn0.2TiO3:0.2%Pr3+,Si4+,Lu3+ phosphors were synthesized by high temperature solid-state method. Crystalline phase, microstructure and luminescence properties of phosphors were characterized with X-ray diffractometer (XRD), electron paramagnetic resonance spectrometer (EPR), microscopic Raman spectrometer and photoluminescence spectrometer, respectively. The results show that phosphor prepared using β-Si3N4 as Si source has the optimal luminescence properties. Phosphors with the addition of ZnO were confirmed to be constituted of CaTiO3, Zn2TiO4 and Ca2Zn4Ti16O38, and CaTiO3 is major phase. EPR spectra confirm that the presence of Pr4+ and[Pr4+Ti3+O3]+ clusters remarkably increase with the Lu3+ addition. Increasing local symmetry of TiO6 clusters with the addition of Si4+ and Lu3+ is verified by EPR and Raman spectra, which is beneficial for the energy transfer of luminescent center Pr3+. The obtained phosphor exhibited the intense red emission centered at 612 nm (originated from 1D2→3H4 transition of Pr3+) with an ideal chromaticity coordinate located at (x=0.670, y=0.330) under 336 nm excitation. Red emission excited by 370 nm remarkably increases with the addition of Si4+ and Lu3+. The synthetic Ca0.8Zn0.2TiO3:0.2%Pr3+,3.2%Si4+ phosphor has the longest average lifetime.关键词：Ca0.8Zn0.2TiO3:Pr3+;β-Si3N4;Lu3+ doped;red long persistence137|131|2更新时间：2020-08-12
- 摘要：In order to realize the experimental measurement and error analysis of flash radiant temperature induced by high-velocity impact, loading system of two-stage light gas gun and measurement system of flash radiant temperature were set up. Polycarbonate projectiles were accelerated to 6 km/s, 3.9 km/s to impact 2A12 aluminum plate vertically, and instantaneous optical pyrometer was utilized to acquire flash signals, at the same time flash radiant intensities and temperatures were calculated by the ratio method under the different impact conditions. Theoretical values of flash radiant intensities were calculated with different wavelengths and temperatures based on Plank radiant law, thus the error analysis could be obtained by comparing the theoretical values with the experimental ones; the flash radiant temperatures and its average temperature were calculated by selecting corresponding flash radiant intensities of different wavelengths according to the methods of two-color and four-color temperature measurement, and the influence of wavelength's selection to flash radiant temperature was analyzed by calculating the standard deviation. The results show that the flash radiant intensities of experimental measurement are lower than the ones of theoretical value, and the selection of wavelength has a great influence on the calculating results of flash radiant temperature from the method of two-color temperature measurement, meanwhile, the bigger interval of wavelength is, the smaller the calculating error becomes (the minimum error is 68.25 K in experiment No.1 and 30.67 K in experiment No.2); the flash radiant temperature calculated by the method of four-color temperature measurement is close to the average temperature (the error is 72.88 K in experiment No.1 and 63.66 K in experiment No.2), therefore, the bigger interval of wavelength and multiple wavelengths should be adopted in order to reduce error during calculating flash radiant temperature.关键词：high-velocity impact;flash radiant intensity;flash radiant temperature;instantaneous optical pyrometer;error analysis118|217|2更新时间：2020-08-12
- 摘要：A new-type transmission-mode NEA GaAs photocathode with the exponential built-in electric field was designed. The two important features of the new-type GaAs photocathode, the time response and the quantum yield, were theoretically studied by numerical methods. The simulation results show that the response time and the quantum yield of the new-type photocathode gradually increase with the widths of absorption layer when the widths are 0.2-1.5 μm. Especially, when the width is 1.1 μm, the time responses are 10 ps, and the quantum yield is 12.5%-20%. So far, compare with previous GaAs photocathodes with other doping modes, this one has the shortest response time in the same condition of the spectral responses. Meanwhile, the two functions of the average decay time and optimal factor of the built-in electric field are obtained under different widths of absorption layers, the former is related to time responses, and under the latter condition the shortest response times are obtained. The above results provide the theoretical and data basis for the design to optimize new-type GaAs photocathodes with ultrafast response.关键词：GaAs photocathode;exponential built-in electric field;optimal factor;time response109|148|0更新时间：2020-08-12
- 摘要：Multiple exciton generation(MEG) is a process whereby multiple electron-hole pairs or excitons are produced upon absorption of a single photon in semiconductor quantum dots(QDs). This effect represents a promising route to increase solar conversion efficiencies in single-junction photovoltaic cells. MEG in Si BC8 QDs is based on impact ionization and statistical Fermi. The power conversion efficiency for Si QDs solar cells was calculated under AM1.5G solar spectrum with the cell temperature at 300 K. For the incident wavelength of 280-580 nm, the power conversion efficiency can be improved by MEG effect for d>5.0 nm Si QDs. For Si BC8 QDs with d=6.3-6.4 nm, the maximum energy conversion efficiency is 51.6%.关键词：multiple exciton generation;quantum dots;photovoltaics126|349|1更新时间：2020-08-12
- 摘要：The effect of V-shaped pit hole current distributionin GaN based green LED was experimentally and theoretically investigated. First, three LED samples were prepared by experiment, which V-shaped pit area ratio was different. Then, a numerical model was established to match the external quantum efficiency(EQE) and the voltage of the theoretical calculation with the trend of the experimental test, thus the credibility of the numerical model was established. Calculation results show that the V-shaped pit changes the distribution of hole current, the hole current density increases significantly in the V-shaped pit, and reduces significantly at the platform. Further, the analysis shows that the hole current ratio in the V-shaped pit shows a near linear increase with the V-shaped pit area ratio(slope is 2.06) when the V-shaped pit area ratio is in the range of 0-10%, while the V-shaped pit hole injection has not yet dominated the whole hole injection process.关键词：V-shaped pits;GaN;green LED;hole current distribution119|252|0更新时间：2020-08-12
- 摘要：NaYF4:Er3+,Yb3+nanocrystals were synthesized and the morphology of nanocrystals was characterized. The nanocrystals were doped into SU-8 as the core material of the optical waveguide amplifier by physical doping method. The size of the waveguide amplifier was optimized. Polymer optical waveguide amplifiers were fabricated on a silica substrate by spin coating, photolithography and ICP etching. In the experiment, the optical waveguide amplifier was prepared by two methods:light bleaching and wet etching. The amplification characteristics of the devices prepared by the two methods are tested. The amplifier prepared using the wet etching method achieves a relative gain of 2.7 dB at 1 550 nm when the pump power is 241 mW and the signal light power is 0.1 mW. The amplifier prepared using the photobleaching method obtains a relative gain of 4.5 dB at 1 550 nm for 235 mW pump power and 0.1 mW signal power. Based on the above test results, the effects of the two processes on the device performance were analyzed.关键词：optical waveguide amplifier;NaYF4:Er3+;Yb3+nanocrystals;polymer137|267|0更新时间：2020-08-12
- 摘要：The highly sensitive Hall device made of InAs/AlSb quantum-well structures pseudomorphically grown on the GaAs substrate by molecular beam epitaxy has been developed. The advanced InAs/AlSb Hall device includes double δ-doped layers, which significantly elevate the sheet electron density. Moreover, electron mobility is increased from 15 000 cm2·V-1·s-1 to 16 000 cm2·V-1·s-1 at room temperature, compared with that of an unintentionally doped AlSb/InAs Hall device. AFM measurement results show a smooth surface morphology and high crystalline quality of the samples. The quantum Hall device can be operated in the temperature ranging from 77 K to 300 K. Hall measurements show different scattering mechanism on electron mobility at temperature range. The advanced highly-sensitive InAs/AlSb heterostructure two-dimensional electron gases(2DEG) Hall device including double δ-doped layers is promising in near future.关键词：Hall device;quantum well;double δ-doping;molecular beam epitaxy116|123|0更新时间：2020-08-12
- 摘要：According to the theoretical model of typical optical materials damaged by ultraviolet excimer laser, a numerical simulation was performed to calculate temperature and thermal stress fields using finite element method. The damage effects of excimer laser on transparent optical material (fused silica) and non transparent optical material (K9 glass) were investigated, and the validity of the theoretical model was confirmed by the experimental results. The simulation results indicate that the laser parameters exhibit a great effect on damage effect and damage threshold. It is worth noting that the melting damage threshold is lower than the stress damage threshold when the repetition rate increases to more than 45 Hz. The thermal damage of excimer laser to the strongly adsorbed impurities on the surface of fused silica is also analyzed. The theoretical analysis is in agreement with the same initial damage morphology of fused silica surface.关键词：laser damage;ultraviolet excimer laser;typical optical material126|182|2更新时间：2020-08-12
- 摘要：Using the illumination formula of single LED wick and the symmetry of large LED rectangular array illumination distribution, a physical model for the illumination uniformity of large LED rectangular arrays was established. The illumination uniformity of large LED rectangular array was derived. This formula is used to study the illumination uniformity of large LED rectangular arrays with the target distance and the ratio of length to width and the m values. The illumination uniformity doesn't linearly decrease with the increasing of the target distance, doesn't linearly increase with the increasing of the ratio of length to width, and linearly increases with the increasing of m value. These rules provide theoretical basis for improving the uniformity of large LED rectangular arrays, the research direction and calculation method are provided for the illumination uniformity design of large LED rectangular array. It makes up for the lack of the uniformity of LED array illumination.关键词：LED;rectangular array;spot radius;uniformity95|297|2更新时间：2020-08-12
- 摘要：Gases can provide many interesting features as media for laser based application. However, the experiments in free space are intrinsically awkward because of the unavoidable diffraction and self-focusing effects at high laser power, which can lead the light to spread out and its intensity to fall as it propagates. We demonstrate a new type of porous core photonic crystal fiber for confining and guiding light in low-refractive-index and subwavelength air holes in the core. The broadband, single mode and low loss guiding properties of the fibers are studied. The propagation mechanism in low-refractive-index and subwavelength-diameter holes is analyzed by electromagnetic theory of optical waveguide transmission and evanescent wave coupling. Tightly confined light in holes, combined with long interaction lengths, provides new conditions for the interaction between light and matter, and enable a variety of applications including gas sensing, nonlinear light management, highly integrated photonics technology, atomic manipulation, etc. Because the holes of core can guide light, the mode field distribution is affected directly by changing the size of the air holes, and the high birefringence property can be obtained. By careful designing of structure parameters of the fibers, high birefringence of B=4×10-2, high birefringence in 5 μm-diameter core, characteristics of large-mode-area, single-polarization and single-mode are obtained. These fibers have wide application prospect in fiber polarizer, filter, optical switch and fiber sensing fields. New methods are provided for the light field regulation.关键词：fiber optics;photonic crystal fiber;hollow core;birefringence;confinement loss112|265|1更新时间：2020-08-12
- 摘要：In order to establish a method to examine copy paper in different brand, model by image processing techniques of video fluorescence spectroscopy (VFS) and inspect and identify copy paper in forensic science, 20 kinds of copy paper in different brands and models were collected, the video spectral comparator (VSC6000) was used to analyze these papers to obtain the fluorescence image of the samples. Combining with the image processing technology, the morphology and the intensity of the fluorescence were analysised visually and quantitatively. According to the morphological features in the VFS obtained by UV-365 nm and powerful light source (400-570 nm) of the samples, the papers can be identified preliminarily. The visual analysis of the samples can be realized by drawing the contour map of video fluorescence image, and the fluorescence image brightness value L can be used to quantify the samples. The results prove that the image processing techniques of VFS can discriminate the copy paper precisely and effectively, which can be used to examine the document material, provide a practical method for the differentiation, comparison, identification in forensic science.关键词：video fluorescence spectroscopy(VFS);image processing;copy paper;forensic science;document examination116|187|0更新时间：2020-08-12
- 摘要：To establish the influencing rules of different light sources on traditional paintings and to determine the minimum damage light source of different types of traditional paintings, we utilized a white light emitting diode(WLED) as experimental light source, a metal halide lamp(MHL), and a tungsten halogen lamp(THL) as contrast light sources to illuminate Chinese paintings, periodically measuring CIELAB color data. First, we calculated the color difference based on the data and plotted color difference against exposure. Then, we plotted fitting curves of color difference against exposure for four pigments, and obtained the relative influence coefficient of different light sources on four organic pigments via analyzing the regression equation. According to the experiment results, for fine brushwork light color paintings, the ratio of the average effect is KMHL:KTHL:KWLED=1.00:0.92:0.84; for small green light color paintings, the ratio of the average effect is KMHL:KTHL:KWLED=2.05:1.71:1.65; for ink light color paintings, the ratio of the average effect is KMHL:KTHL:KWLED=1.17:0.94:0.91. According to the above results, for the three types of Chinese traditional light color paintings, the illumination damage from RYGB-type WLED is less than metal halide lamp and tungsten halogen lamp. The RYGB-type WLED is the light source resulting in the least damage to the painting colors.关键词：Chinese traditional painting;WLED;color decay;illumination protection120|203|1更新时间：2020-08-12
- 摘要：To provide high quality, more safe and intelligent lighting source, the linear dimming mixed lighting system and its dimming and color modulation method were established based on the cold and warm white LEDs. The mixed lighting source set the light color and intensity using color temperature and lightness, which was more accord with humanized requirements. In the procedure of system intelligent light distribution optimization, the color temperature was converted to chromaticity coordinate on the CIE u'v' diagram and the lightness was converted to luminance, which made the optimizing computation more precise. The system adopted linear dimming method to avoid safety risk induced by flicker, and the adopted optimization algorithm solved the big color shift problem of linear dimming. The experiment results show that the chromaticity stability of the mixed lighting system can keep within 1-step CIE u'v' circle, which means with specific chromaticity setting, there is no perceivable chromatic aberration. The theoretical research and experiment results show that the mixed lighting system is simple, practicable and with high practical value.关键词：white LED;mixed lighting;linear dimming;chromatic aberration;CIE u'v' circle124|281|3更新时间：2020-08-12
- 摘要：The col-linear double pulse laser induced breakdown spectroscopy(Laser induced breakdown spectroscopy, LIBS) technology was used to detect fenthion in solution. The fenthion solution was enriched with graphite. The LIBS spectra of samples were obtained by double channel high-precision spectrometer. The carbon spectral line(C Ⅰ 247.856 nm) was used as internal standard to adjust spectral line of 210-260 nm. Then, the competitive adaptive reweighted sampling(Competitive adaptive reweighted sampling, CARS) was used to screen important variable wavelengths which related to fenthion. Finally, the least squares support vector machine(Least squares support vector machine, LSSVM) was used to establish the calibration model of fenthion, and the model was compared with the standard calibration model which established by the basic calibration method and the internal standard method. The results show that the col-linear double pulse LIBS technique can be used to detect the content of fenthion in solution. Optimum calibration model's fitting degree R2 of basic calibration method is 0.935 04. The prediction relative error(Prediction relative error, PRE) of prediction samples is 41.50%. While fitting degree R2 of internal standarad method is 0.993 61, and PRE of prediction samples is 14.91%. What's more, fitting degree R2 of internal standard and CARS-LSSVM method is 0.998 6, and PRE of prediction samples is 8.06%. Comparing the three types of calibration models, it can be found that the internal standard and CARS-LSSVM calibration model has the best performance. The calibration model which established by internal standard method is second. And the calibration model which established by the basic calibration method is the worst. It can be seen that the CARS method can effectively screen the important variables which related to fenthion. Internal standard method combined with CARS and LSSVM methods can improve calibration model's performance and improve the accuracy of predicting.关键词：laser induced breakdown spectroscopy;internal standard method;competitive adaptive reweighted sampling;least squares support vector machines;fenthion138|216|4更新时间：2020-08-12
- 摘要：An algorithm of nonlinearity noise led by LED nonlinearity was proposed. The signal-to-noise ratio and bit error rate of visible light communications system with OOK modulation could be obtained through the algorithm. The curve about the relation between LED bias point and bit error rate were plotted with Matlab simulation. The results were proved by visible light communication system image transmission experiment. The curve has great significance on the choice of proper LED model and bias point about VLC system experiment.关键词：visible light conmunication(VLC);white LED;OOK modulation;nonlinearity noise;bit error rate(BER)133|206|3更新时间：2020-08-12
- 摘要：A multichip LED device has complex interaction and mechanism due to thermal coupling effect. An estimation method for the thermal network model of the multichip LED device based on multichip thermal model was proposed in this paper. The predicted junction temperature in finite volume method was applied to the multichip LED device. The minimum, maximum and average deviations of junction temperature between the proposed model and the measurement are about 0.8%, 6.8% and 3.4%, respectively. The calculated results are in good agreement with the measurements. These results confirm that the multichip thermal model with finite volume method can provide accurate predictions for junction temperature. The work offers a new research and development tool for practicing LED designers to accurately predict the junction temperature of LED system.关键词：multichip light-emitting diodes device;thermal characteristics;thermal coupling effect;junction temperature;finite volume method115|215|2更新时间：2020-08-12
- Address：No.3888 Dong Nanhu Road, Changchun, Jilin, China Postal code：130033
- Tel：0431-86176862 Email：fgxbt@126.com
- Technical support is provided by Beijing Founder electronics co., LTD 吉ICP备11002662号-17
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0