最新刊期
卷 36 ， 期 5 ， 2015
- 摘要：NaYF4:Yb3+,Tm3+/CdSe nanoheterostructures with NIR-to-NIR upconversion luminescence were synthesized by a two-step improved wet-chemical method. X-ray diffraction (XRD) characterization shows that the nanoheterostructures are composed of both pure hexagonal phase NaYF4:Yb3+,Tm3+ and wurtzite phase CdSe. Upconversion emission spectra under the excitation of 980 nm near-infrared laser show that 797 nm emission from Tm3+ ions has been enhanced greatly, while neither ultraviolet nor blue emissions of Tm3+ appear compared with that of pure NaYF4:Yb3+,Tm3+. It indicates that the energy transfer occurs between NaYF4:Yb3+,Tm3+ and CdSe. Under 980 nm excitation, the energy absorbed by Yb3+ ions transfers to Tm3+ ions, then transfers to CdSe partially, and finally the excited CdSe returns the energy back to the corresponding energy levels of Tm3+. These processes lead to the quenching of UV and blue emissions and the enhancement of 797 nm emission of Tm3+ ions in the NaYF4:Yb3+,Tm3+/CdSe nanoheterostructures. The excitation (980 nm) and emission (797 nm) are both located in the NIR spectral range (700-1 100 nm) that is referred as the "optical window" of biological tissues because of the minimum of light scattering and autofluorescence of tissue and a relatively large penetration depth. Therefore, the present NaYF4:Yb3+,Tm3+/CdSe nanoheterostructures could have potential applications in biology and biomedicine fields.关键词：NaYF4:Yb3+;Tm3+;CdSe;nanoheterostructures;upconversion luminescence;energy transfer129|78|2更新时间：2020-08-12
- 摘要：Two-dimensional electron gas (2DEG) with high-mobility was found in wurtzite ZnO/Zn1-xMgxO heterostructures which probably arises from the polarization discontinuity at the ZnO/Zn1-xMgxO interface. In this paper, we studied the polarization properties of Zn1-xMgxO alloy at different Mg composition using first-principles calculations with GGA+U method, and the polarization properties were calculated according to Berry-phase method. In addition, the polarization was divided into three parts:electronic polarization, iron polarization and piezoelectric polarization. The results indicate that the piezoelectric polarization is the most important part in these contributions.关键词：ZnO;MgZnO;spontaneous polarization;Berry-phase method105|159|1更新时间：2020-08-12
- 摘要：α-NaYF4:5%Eu3+ red phosphors were prepared by the solvothermal method. The crystal structure, morphology, luminescence properties and the chromaticity coordinates(CIE) were discussed under different annealing temperature, and three samples of them were coated with SiO2 before annealed in air. It is found that the forbidden 5D0→7F0 transition emerges after annealing treatment, and all the characteristic emission peaks of Eu3+ are enhanced with the increasing of annealing temperature, correspondingly the CIE turns to red. But the nanoparticles reunite each other under high annealing temperature, and the tendency of CIE turning to red is slower. Based on the results of asymmetric ratio σ, we consider the appearance of 5D0→7F0 transition is from Eu3+ deviating from the inversion symmetry center.关键词：solvothermal method;α-NaYF4 nanocrystal;annealing;luminescence106|31|2更新时间：2020-08-12
- 摘要：The band structure, density of state, magnetic and optical properties of Co doped zinc blende ZnO were systematically studied by using the first-principles based on the spin polarized density functional theory. The calculated results show that the ground state of Co doped zinc blende ZnO is antiferromagnetic and shows metal characteristics, while the ferromagnetic state shows the half-metallic characteristics. For the ferromagnetic coupling state, strong spin-orbit coupling appears near the Fermi level and shows no obvious asymmetry for up and down spins, which indicates a significant hybrid effects from Co 3d and O 2p states. The magnetic moments are mainly contributed by unpaired electrons in Co 3d and neighbor O 2p orbital and are correlated to the doped site of Co atoms. In addition, the calculated results of optical properties show that Co doped zinc blende ZnO has a strong absorptive capacity at the visible light, and the absorption peaks have red shift in the high energy region. The theoretical calculated results demonstrate that Co-doped zinc blende ZnO may become excellent magneto-optic materials.关键词：Co-doped;zinc blende ZnO;first-principles;ferromagnetic and anti-ferromagnetic;optical properties123|234|1更新时间：2020-08-12
- 摘要：CdTe/bentonite composites were successfully prepared by using CdCl2 and Na2TeO3 as reactants and ascorbic acid as reducing agent. The obtained samples were characterized by X-ray diffraction (XRD), fluorescence spectrophotometer and ultraviolet-visible spectra (UV-Vis). The effect of CdTe/bentonite composites on photocatalysis degradation of methyl orange was investigated in detail. Under irradiation by mercury lamp for 60 min, it was found that 66.23% of degradation rate was achieved when the dye initial concentration was 10 mg/L. The experiment results show that the performance of CdTe/bentonite composites catalyst is superior to pure CdTe quantum dots.关键词：CdTe;bentonite;photocatalysis;degradation112|177|1更新时间：2020-08-12
- 摘要：The pentacene-based organic field-effect transistor (OFET) with a thin transition metal oxide (MoO3) layer between pentacene and metal (Al) source/drain electrodes was fabricated by using substrate heating. The effects of substrate heating and MoO3 modifying electrodes on their performance were investigated. Comparing with OFET which only has metal Al source/drain electrodes, the performance of device with 10 nm MoO3 buffer layer is significantly enhanced under 60℃ substrate temperature. The field-effect mobility increased from 3.39×10-3 cm2/(V·s) to 2.25×10-1 cm2/(V·s), meanwhile the threshold voltage decreased from 12 V to 3 V, respectively. The enhanced performances are attributed to the improvement of the high efficiency of carrier transportation and injection, which were introduced by heating substrate and inserting MoO3 buffer layer between electrodes and active layer. Therefore, the means of substrate heating and electrodes modification are indispensable for high performance OFET.关键词：organic field-effect transistors;substrate heating;electrodes modification;carrier injection and transportation123|156|0更新时间：2020-08-12
- 摘要：The dispersion characteristics of organic/polymer optical rib waveguide affect the performances of polymer photonic devices greatly. In this paper, the effective refractive index of optical rib waveguide was calculated by scalar variational formula, and the distribution of optical field used was obtained by using effective index method (EI) approximately. Considering the transverse variations of refractive index distribution and based on the vector wave equation governing the guided modes, the effective index obtained by scalar variational formula (VEI) was modified by perturbation method (PM) for precise dispersion characteristics. The dispersion characteristics of the fundamental and higher order modes were analyzed for polymer multimode rib waveguides. An approach was provided to investigate the effect of the structure parameters and dimensions on the polarized dispersion characteristics of the fundamental and higher order modes for TM, TE modes. The polarized dispersion characteristics of single mode waveguide were analyzed for TM, TE fundamental modes. It is demonstrated that the dispersion characteristics of TM mode obtained by eigenvalue equation must be modified duo to the large error, and the error for TE mode is small relatively.关键词：integrated optics;optical waveguide;optical polymer materials101|225|1更新时间：2020-08-12
- 摘要：The effects of p-InGaN layer thickness on the performance of p-i-n structure InGaN solar cells were investigated. Through theory calculation, it is found that the conversion efficiency of InGaN solar cells decreases with the increasing of p-InGaN thickness. The poor Ohmic contact properties of metal to p-InGaN also have a negative effect on the performance of InGaN solar cells. The short-circuit current reduces obviously with the increasing of p-InGaN thickness, simultaneously the conversion efficiency of InGaN solar cells decreases. The performance of InGaN solar cell could be improved by employing a relatively thin p-InGaN layer.关键词：InGaN;solar cell;p-i-n structure125|209|3更新时间：2020-08-12
- 摘要：In order to improve the energy conversion efficiency of organic solar cells (OSCs), the moth-eye structure was applied to OSCs. According to the theoretical simulation, in a certain active layer thickness, the moth-eye OSCs has a large enhancement in light absorption efficiency compared with the planar OSCs. Through the optimization of microstructure morphology, period and height, the moth-eye OSCs has an increase of 11.3% in light absorption efficiency than the planar OSCs. The simulation of the distribution of magnetic field intensity in the moth-eye OSCs indicates that the light absorption enhancement can be attributed to both the anti-reflective effect of moth-eye structures and the enhanced absorption effect of the surface plasmon polariton (SPP).关键词：organic solar cells;moth-eye structure;surface plasmon polariton;absorption efficiency97|192|4更新时间：2020-08-12
- 摘要：Flexible electrodes with high conductivity and transparence are still great challenges in the fabrication of stretchable optoelectronic devices. In this experiment, we demonstrated a flexible hybrid electrode based on reduced graphene oxide (RGO) and silver nanowires (AgNW). The RGO was prepared by thermal reduction and hydrazine reduction of graphene oxide to partially remove the oxygen-containing groups and to restore its electrical properties. We employed AgNW to restore the defects in RGO films, such as grain boundaries and wrinkles, to improve the conductivity of the electrodes. By optimizing the processing conditions, the flexible hybrid electrode exhibited excellent optical and electrical characteristics as well as mechanical flexibility. The optical transmittance and sheet resistance of the hybrid electrode were 62% at 550 nm and 420 Ω/□. The RGO/AgNW hybrid electrode shows the potential for a wide range of flexible and stretchable optoelectronic device applications.关键词：RGO;silver nanowire;flexible electrode125|121|6更新时间：2020-08-12
- 摘要：Based on p+ source/drain region and n-well of standard CMOS technology, two forward-injection-type Si-LEDs with different petaloid configuration were designed and fabricated by UMC 0.18 μm 1P6M CMOS process. The measurement results indicate that the emission spectra of both Si-LEDs locate at near-IR region with peak wavelength around 1 130 nm, and the devices can operate properly below 2 V. When the device TS2 with eight-petal configuration is forward-biased at 200 mA, its optical power increases to 1 200 nW without saturation, and the maximum power conversion efficiency reaches up to 5.8×10-6 at the current of 40 mA, which is almost double that of the device TS1 with four-petal. Due to the features of low operating voltage and high conversion efficiency, the device TS2 is highly attractive for future optoelectronic applications.关键词：Si-based light emitting diode;forward-injection;wedge configuration;standard CMOS technology106|123|0更新时间：2020-08-12
- 摘要：A new type of random laser structure composed of ZnO particles and Au which embedded in waveguide is proposed. The distribution of the optical filed and the modes spectra in the random laser system are numerically simulated by using the finite difference time domain (FDTD) method. We also compare and analyze the optical field and the modes spectra of random laser by using Au particles and Au film, respectively. The results show that when Au particles were embedded in waveguide, the number of modes reduced and the monochromaticity was better than Au film which only had a better laser output intensity.关键词：ZnO random particles;random lasers;finite difference time domain;pattern spectrum103|158|2更新时间：2020-08-12
- 摘要：Based on the stack array of structure and assembly methods, a set of high temperature and hard solder quasi-continuous laser diode stack arrays were developed, and the related photo-electric performance and lifetime characteristics were studied. When the stack array is in condition of operating current 200 A, repetition frequency 250 Hz, pulse width 200 μs, the FWHM is less than 3 nm, electro-optical conversion efficiency is more than 50%, peak power per bar is more than 200 W, lifetime is up to 4.71×109 shots, and the peak power degradation is less than 15%. When the operating current is 150 A, the lifetime is up to 1.5×1010 shots.关键词：diode laser array;hard solder;QCW113|290|4更新时间：2020-08-12
- 摘要：A 500-μm-long cavity laser diode with 5 layers of InAs quantum dot was fabricated. The laser materials were grown by gas-source molecular beam epitaxy. For the first time, the linewidth enhancement factor was acquired by gain fitting and weighted wavelength. Gain fitting is an important complement to Hakki-Paoli method, and plays an important role in evaluating whether the gain is saturation. The differential modal gain was evaluated by numerical differentiation of the maximum modal gain. The differential modal gain showed a maximum of 1.33 cm-1/mA at 50 mA, and dropped off to 0.34 cm-1/mA at 57 mA (≈0.99Ith). The weighted average wavelength was treated as central wavelength in order to calculate the wavelength movement. It was found that Δλ decreased slowly until closed to zero. The new method avoids the error due to selecting the data points, and the value of linewidth enhancement factor is from 0.12 to 2.75.关键词：gain;differential gain;wavelength shifts;linewidth enhancement factor112|192|2更新时间：2020-08-12
- 摘要：Vertical cavity surface emitting laser (VCSEL) with external cavity which is filled by dielectric materials or air can achieve good beam quality and high power. Aiming at the problem of complex production process and loose structure of the external cavity, a kind of surface emitting laser with the dielectric film integrated on external cavity bottom substrate was designed. Multilayer dielectric insulation films grown on the surface of substrate, N-DBR, and P-DBR composed the coupled cavity structure, and the substrate was served as external cavity of VECSEL. This structure can suppress high order mode, so it can optimize the output spectrum and far-field divergence angle of beam characteristics. Based on the previous theory, we manufactured a VECSEL with active area of 200 μm in diameter and external cavity length of 250 μm. The device is carried out with continuous DC current of 3.4 A at room temperature, and the power is 260 mW, the divergence angle of far field is 3.8°,the full width at half maximum of spectrum is 0.046 nm. Obviously, compared with conventional structure of bottom emitting VCSEL, the beam quality of VECSEL devices is improved.关键词：vertical-external-cavity surface-emitting lasers;coupled-cavity;spectrum;far-field divergence angle141|263|2更新时间：2020-08-12
- 摘要：According to the basic 2T1C pixel circuit, the calculation model of AMOLED panel and TFT parameters was established. The relationships of AMOLED display size with mobility of TFT, metal sheet resistance, refresh rate and TFT device structure were analyzed in detail. In the design of large size high resolution AMOLED panel, RC delay of signal line is the main limiting factor. The enhancement of TFT mobility is benefit for large size display panel within a certain range. Reducing the RC delay is the key technology to realize the large size, high resolution, high refresh rate display. Developing the copper wiring technology and TFT device structure with low parasitic capacitance is the key technology of large size AMOLED display in the future.关键词：AMOLED;Large size;high resolution;RC delay204|425|3更新时间：2020-08-12
- 摘要：The optical simulation is an important method for white LED illumination design, but it is too heavy of computation to get some reliable results in a color distribution simulation by using an ordinary computer. To reduce the amount of calculation, the chromatic relations and the point-to-point method are employed, as well as the numerical fitting method and pixels synthesis are introduced to decrease the fluctuation of correlated color temperature of optical simulation results. The validity of the above two methods is demonstrated by comparing with the experimental results, and the performance of color simulations is improved greatly.关键词：white LED;correlated color temperature;optical simulation114|384|4更新时间：2020-08-12
- 摘要：Out-field laser jamming experiment of single CCD colour imaging system irradiated by multi-wavelength laser (750-970 nm) was done. Laser jamming effects of colour CCD imaging system with different irradiating conditions were measured at 1.3 km. Laser jamming model was set up, and theoretical proving and analysis on experimental results were completed. Theoretical and experimental results show that the jamming effect of laser on colour CCD imaging system is obvious, CCD surface appears obvious light saturation and crosstalk phenomena. The light saturation phenomenon is caused by laser diffraction effect. In addition, laser jamming effect and light saturation gradually enhance with the increasing of the laser power density to target. When the laser power density to target of single wavelength 750 nm laser is 4.2 kW/cm2, the light saturation area of CCD surface is 0.88 mm×0.97 mm. When the laser power density to target of multi-wavelength laser is 20.7 kW/cm2, CCD device appears the whole target saturation. The simulation results are coincident with the experimental results, and it proves that the laser jamming model is correct. The simulation results for far-field laser jamming show that the laser jamming effect gradually weakens with the increasing of laser jamming distance.关键词：laser jamming;colour CCD device;semiconductor laser;light saturation and crosstalk157|171|3更新时间：2020-08-12
- 摘要：A research method of analysis of the road lighting source safety and energy-saving properties under the human mesopic conditions was given. By constructing the reaction time test system for road lighting under the mesopic vision, the luminous efficiency model was established and luminous efficiency curve was obtained. By using this model, the evaluation method of energy efficiency based on the lighting power density was given. Using the calculation and analysis method of the color-rendering properties based on the color-rendering index, the effect of the changes in relative spectral power distribution on the color of light source was discussed under Luv uniform color space, and the function expression between the dominant wavelength of the light source and color-rendering index was established, which can be used to obtain the relationship between human sensitivity and light source color of each wavelength point. The above method was verified by the reaction time simulation test and the definition of the road lighting picture calculation experiment. The results show that the green-white light source with dominant wavelength of 540-550 nm has the best power-saving and color-rendering properties under the mesopic vision.关键词：reaction time;luminous efficiency model;lighting power density;color-rendering properties132|219|1更新时间：2020-08-12
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