最新刊期
卷 30 ， 期 2 ， 2009
- 摘要：BaMgAl10O17 : Eu2+(BAM) is the blue phosphor component of three-color fluorescent lamps and plasma display panels(PDP).In present paper the emission spectra lineshape of BAM were investigated by using lattice relation and theory of multiphonon transitions.The result indicated that the broadening emission band of BAM can be fitted by three Gaussian functions very well, the transitions from three different site of Eu2+ in the BAM lattice forms the BAM emission spectra, the two of the emission centers are assigned to Eu2+ at normal Beevers-Ross sites and anti-Beevers-Ross sites, respectively, but the third luminescence center may be located at mid-oxygen (mO )sites.关键词：BAM;lineshape;multiphonon transiton;emission spectrum142|92|1更新时间：2020-08-12
- 摘要：In this paper, we reported the spectroscopic properties of praseodymium ions (Pr3+) doped transparent oxyfluoride glass ceramic excited with different laser lines, such as 532, 514.5 and 476.5 nm. and the spectroscopic features of Pr3+ ions in LaF3 nanocrystals (NCs) and in oxide glass were presented. It was found that the population on 3P0 state of Pr3+ ion in NCs and in glass can be achieved by multi-phonon assistance process when excited by 514.5 nm laser lines. As a comparison, 476.5 nm laser line which is mainly resonant with the 3H4 to 3P0 transition of Pr3+ ions in NCs is used as the excitation source, transitions from 3P0 state to many lower states, such as 3H5, 3H6, 3F2 manifolds were observed and it showed significant difference from those excited by 532 nm and 514.5 nm laser lines in which only transition from 3P0 to 3H5 exists. We attribute those different spectroscopic features as selectively excitation of Pr3+ ions in different environments where exist strong/weak electron-phonon coupling in the 3P0,1 states of Pr3+ ion in NCs and in glass. Crystallization behavior and vibrational properties of transparent glass ceramic were also stu-died by Raman spectroscopy excited by 532 nm and 514.5 nm laser lines.关键词：transparent oxyfluoride glass ceramic;praseodymium;nanocrystals110|636|0更新时间：2020-08-12
- 摘要：The piecewise linear current density recursive convolution (PLCDRC) finite-different time-domain (FDTD) method for magnetized plasmas was applied to study the characteristics of the one dimension time-varying magnetized plasma photonic crystal forbidden band gaps. The electromagnetic propagation process of a Gaussian pulse through a time-varying magnetized plasma photonic crystal was investigated. The transmission coefficients through time-varying magnetized plasma photonic crystals were calculated, and the effects of periodic constant, plasma temperature and density on characteristics of band gap structure for magnetized plasma photonic crystals were analyzed with them. The results illustrated that the different band gaps can be gotten by changing the rising time and density of plasma.关键词：magnetized plasma photonic crystals;photonic crystals;finite-difference time-domain method;forbidden band gap106|138|8更新时间：2020-08-12
- 摘要：The called doping superlattice is that n-type and p-type impurity are doped alternately on a substrate material, thus forming 1-dimension periodic structure with n-i-p-i-n-i-p-i…arrange.The conductor band botton of the substrate material is modulated periodically by alternately dopping, leading to shape similar to sine-squared potential.The particle motion equation is reduced to the general pendulum equation with a dampping and a force terms in the classical mechanics frame based on the bistable state effect of the superlattice quantum well. The equations solution and the period of a particle motion are found strictlly by Jacobian ellipse function and the 1st kind ellipse integral for the non-perturbed system.The global bifurcation and a chaotic behaours with the Smale horseshoe were analysed by Melnikov method.The critical condition through to a chaos based on a cascade bifurcation was found. It shown that the chaotic oscillation with the Smale horseshoe exits in the system for the separatrive orbit; odd-order subharmoric bifurcations found also for the oscillation periodic orbit.Noting to critical condition entered in a chaos being related to the parameters of the system, the chaos can be avoided or controlled.The theoretical analyse is provided to the design of the optical bistable state cell.关键词：dopping superlattice;quantum well;sine-squared potential;general pendulum equation91|138|0更新时间：2020-08-12
- 摘要：Quantum dot system has attracted a lot of attention as a possible candidate for the parts of an apparatus of quantum function, due to the potential applications foreground and a great deal of novel optoelectronic and transport properties.But owing to the research of electronic properties in quantum dot being very important, so more and more researchers started to study the quantum dot properties both theoretically and experimentally.However, for the convenience, in those works, people only confine themselves to discuss zero Kelvin limit condition.In fact, researching the excitation properties in low-dimension structures under finite temperature is considerably important for improving and enhancing the calorifics performance of fundamental elements.In this paper, the influences of temperature on magnetopolaron in parabolic quantum dot were studied by using the methods of a linear combination operator,LLP transformation, and quantum statistics, and the dependences of the ground state energy of magnetopolaron and the ground state bound energy to the confinement strength of quantum dot,the cyclotron frequency (magnetic field) and the temperature were obtained.Numerical calculation results illustrate that: <br>
(1) The ground state bound energy </em>E<em><sub>b</sub> of magnetopolaron increases with the increasing of cyclotron frequency.<p/>
(2) Although the changes of ground state energy </em>E<em><sub>b</sub> in a magnetic field with cyclotron frequency </em>ω<em><sub>c</sub> are related to the temperature parameter </em>γ<em>, but the change laws of the </em>E<em><sub>b</sub> for different </em>γ<em> as a function of </em>ω<em><sub>c</sub> are similar.<br>
(3) The ground state bound energy </em>E<em><sub>b</sub> in a magnetic field decreases with the increasing of temperature parameter </em>γ<em>.Generally, the change of the ground state bound energy </em>E<em><sub>b</sub> with temperature parameter </em>γ<em> is more obvious when the temperature parameter </em>γ<em> is smaller, but the change of the </em>E<em><sub>b</sub> with </em>γ<em> is not remarkable when the temperature parameter </em>γ<em> is bigger.<br>
(4) The scope of the ground state bound energy </em>E<em><sub>b</sub> of magnetopolaron decreases with the increasing of the temperature parameter </em>γ<em>, it not only depends on the temperature parameter </em>γ<em>, but also on the cyclotron frequency </em>ω<em><sub>c</sub>, and the </em>γ<em> changing range with </em>E<em><sub>b</sub> decreases with the increasing of cyclotron frequency </em>ω<em><sub>c</sub>.<p/>
(5)The ground state bound energy </em>E<em><sub>b</sub> of magnetopolaron increases with the increasing of the confinement strength </em>ω<sub>0</sub>.关键词：parabolic quantum dot;magnetopolaron;ground state binding energy;temperature dependence98|171|0更新时间：2020-08-12 - 摘要：Photonic crystal materials (PCs) are the new research fields of materials in the recent years. Because of its features of photonic localization and photonic band gap (PBG), the photonic crystals changed traditional physical processes in it, and some new features and phenomena occur. The energy transfer in the photonic crystals is also affected. Through the research of energy transfer in PCs, a theory basis of this process will be established to guide the preparation experiments of luminous materials based on the PCs.<p/>In this paper, a kind of semi-classical theory was proposed based on the theory of photonic crystals and energy transfer in solid state to explain and analyze the process of energy transfer in 1-D PBG. A method to solve the similar problems was also generalized. We found out that the resonance dipole-dipole interaction (RDDI) plays a major role in the energy transfer. Effects of the photonic band gap modulation are reflected on the dispersion relation. So the dispersion relation can be introduced into the calculation of transition matrix. The related factors and mechanisms of the discussion about the energy transfer in PCs are concluded, finaly.关键词：photonic crystals;energy transfer;photonic band gap;dispersion relation;RDDI104|402|1更新时间：2020-08-12
- 摘要：Generally in semiconducting polymers, holes are majority carriers while electrons as minority,the carrier misbalance between electrons and holes further deteriorate in the fact that hole usually take possession of higher mobility and smaller injection barrier. To balance the electrons and holes in luminous layer, there are two commonly used stratagems. One is to improve the injection of electrons such as employ low work function metals such as barium and calcium as cathode though they are susceptible to degradation upon water vapor and oxygen or proposed to inser an insulating thin layer usually metal fluoride between polymer/electrode interfaces to build a bilayer cathode.Another is adding a layer into the polymer light-emitting diode such as hole buffer layer or electron-blocking layer.In this work, a layer of small organic molecule (CBP, dissolved in chloroform) was added into the polymer light-emitting diode between the anode (ITO) and luminous layer (MEH-PPV), using spin-coating method. The influence of different CBP concentrations was investigated. A typical single-organic-layer polymer light-emitting diode device which were constituted with anode (ITO), luminous layer (MEH-PPV) and cathode (LiF/Al) was employed as reference one. The layer of CBP acts as the hole buffer layer at low voltage and electron-blocking layer at high voltage. Comparing with the single-organic-layer (MEH-PPV) devices, the current efficiency of the composite structure devices is significantly enhanced. The experimental results showed that, below the voltage of 5 V, the current of the composite structure device is higher than that of the single-organic-layer device resulting in the reduction of the turn-on voltage of device. However, when the voltage is higher than 5 V, the current of the composite structure device is lower than that of the single-organic-layer device. That was because, in the low voltage, the CBP layer can slow down the injection speed of the holes into the luminous layer and restricted the holes in the CBP buffer layer. Thus, a built-in electric field was formed in the device, which could improve the transmission of electrons from the cathode to the anode, resulting in the increasing of current, reduce the turn-on voltage and improve the luminous efficiency. However, with increasing of voltage, the CBP layer acts as electron-blocking layer, which limits the electron leaking to the anode. Moreover, as the hole acts as majority carrier, the minority carrier, i.e. electrons, can still combine with holes efficiently which had little influence on the luminance intensity. Therefore, the electron-hole current density balance is improved, luminous efficiency is enhanced. When the CBP concentration is 20 mg/mL, the optimum of current efficiency and luminous intensity is achieved.关键词：CBP;MEH-PPV;polymer light-emitting diodes;current efficiency117|114|0更新时间：2020-08-12
- 摘要：Microchip lasers are miniature diode-pumped solid-state lasers with a sufficiently short thickness of gain media, so only a single longitudinal mode falls under the gain profile. In order to absorb the pump light fully, especially, for the Yb<sup>3+</sup> ions with smaller absorption cross section than the Nd<sup>3+</sup>, quite high concentration of active ions in the laser material is necessary. The Yb<sup>3+</sup> ions can be doped into the GAB host as high as 100% </em>i.e.<em> YbAl<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub>, while keeps the R32 structure due to the radius of the Yb<sup>3+</sup> ion is close to that of the Gd<sup>3+</sup>. This character displays that Yb<sup>3+</sup> mole fraction may be adjusted freely in the GAB crystal without the distortion of the crystal structure. This is very important for a microchip laser medium since the concentration of active ions is generally modified with the thickness of the microchip for absorbing adequate pump power and making the laser operates effectively. So the Yb∶GAB crystal with changeable Yb<sup>3+</sup> mole fraction could be a good candidate for microchip laser medium.<p/>
The polarized absorption spectra, emission spectra of Yb<sup>3+</sup>-doped GdAl<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub> (Yb∶GAB) crystals with a series of Yb<sup>3+</sup> mole fraction from 0.125~1.000 were measured at room temperature.<p/>
From the polarized absorption spectra of Yb∶GAB crystals at room temperature, it can be found that the σ-polarized (</em>E⊥c<em>) absorption coefficient is larger than that of the π-polarized (</em>E‖c<em>) at the same Yb<sup>3+</sup> mole fraction. The 976 nm peak is the strongest absorption peak in the σ-polarized, which can match the emission wavelength of InGaAs laser diode (LD). It means this kind of crystal is suitable for LD pumping. <br>
Samples of powder and diluted powder of all the Yb∶GAB crystals were also used in the spectral experiments to reveal and eliminate the effect of radiation trapping on the measured emission spectra. The emission cross sections of the Yb∶GAB crystals obtained by means of the reciprocity method (RM) and the Fuchtbauer-Ladenburg formula were compared in order to study the radiative trapping effect on the emission spectra. The influence of Yb<sup>3+</sup> mole fractions on the effect of radiation trapping was analyzed on the basis of the experimental results. It can also be found from the emission spectra of Yb∶GAB crystals with different Yb<sup>3+</sup> mole fraction that, with the increment of Yb<sup>3+</sup> mole fraction, the cross section of the first emission peak (left,in Fig.2) decreases and the peak red shifts but the cross section of the second emission peak (right) increases. The effect of radiative trapping increases with the Yb<sup>3+</sup> mole fraction increasing. Therefore, the shift between the barycenters of the measured and the intrinsic emission spectra, Δ</em>λ<em>, was proposed as an appraisement of the radiation trapping effect and an empirical relation between Δ</em>λ and Yb<sup>3+</sup> mole fraction in the Yb∶GAB crystals was deduced. The diluted method can effectively eliminate the effect of radiative trapping on the emission spectra, whereas the powder method can omitting do it at low doping mole fractions. It is impossible to eliminate the effect of radiation trapping on the emission spectra of bulk samples by directly measuring.111|96|1更新时间：2020-08-12 - 摘要：(Y<sub>0.94-<em>x</em></sub>, Eu<sub>0.06</sub>, Bi<sub><em>x</em></sub>)<sub>2</sub>O<sub>3</sub>(<em>x</em> = 0, 0.01~0.06) phosphor powders were prepared by microwave hydrothermal processing. The powders were characterized by XRD, SEM, EDS, photoluminescence and HRTEM. The growth of the crystal face (211) was restrained, resulting from Bi doping probably. The intensity of the emission spectra was generally enhanced when excited with 346 nm owing to Bi doping. It was raised first and then declined later on, and achieved a maximum when <em>x</em>=0.03, indicating that the phosphor powders can serve in near-UV band of 320~375 nm excitation, for example, for white LED and high pressure mercury discharge lamps. The intensity of the emission spectra was generally weakened when excited with 254 nm due to Bi doping, suggesting that the phosphor powders as mentioned are not suitable for the low-pressure mercury discharge lamps.103|99|2更新时间：2020-08-12
- 摘要：Li<em>M(M</em>=Ca, Sr, Ba)BO<sub>3</sub>∶<em>Re</em><sup>3+</sup>(<em>Re</em>=Eu, Sm) phosphors were synthesized by solid state reaction, and their luminescence characteristics were investigated. The emission spectra of Li<em>M(M</em>=Ca,Sr,Ba)-BO<sub>3</sub>∶Eu<sup>3+</sup> phosphors show several bands, and the main emission peaks correspond to the <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>1</sub>(590, 595 and 594 nm), <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>(610, 615 and 613 nm) and <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>3</sub>(654, 651 and 651 nm) typical transitions of Eu<sup>3+</sup>. The excitation spectra show that these phosphors can be effectively excited by 369, 400 and 470 nm. The emission spectra of Li<em>M(M</em>=Ca,Sr,Ba)BO<sub>3</sub>∶Sm<sup>3+</sup> exhibit several bands, corresponding to <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>5/2</sub>(561, 563 and 560 nm), <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>7/2</sub>(602, 599 and 597 nm) and <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>9/2</sub>(651, 647 and 644 nm) typical transitions of Sm<sup>3+</sup>. The excitation spectra show that these phosphors can be effectively excited by 374 and 405 nm. Therefore, the two kinds of phosphors are promising red phosphors for white LEDs. Effects of activation and charge compensation on the luminescence intensities of Li<em>M(M</em>=Ca, Sr, Ba)BO<sub>3</sub>∶<em>Re</em><sup>3+</sup>(<em>Re</em>=Eu, Sm) phosphors were studied, and the results show that the intensities were obviously influenced. Under the conditions of charge compensator Li<sup>+</sup>, Na<sup>+</sup> or K<sup>+</sup> incorporated in these phosphors, the emission intensities of these phosphors were enhanced. The all results illuminate that Li<em>M(M</em>=Ca, Sr, Ba)BO<sub>3</sub>∶<em>Re</em><sup>3+</sup>(<em>Re</em>=Eu, Sm) phosphors are promising red phosphors for white LEDs.141|92|6更新时间：2020-08-12
- 摘要：In recent years, the borate-based phosphors have attracted great interest due its easy synthesis, low preparative temperature and high fluorescent yields. Many borates which contain BO<sub>4</sub> group have attracted more and more attention, because the tetrahedral structure of BO<sub>4</sub> can restrain the oxidation of divalent rare-earth ions. The typical representations of better borate matrix are SrB<sub>6</sub>O<sub>10</sub>, Sr<sub>2</sub>B<sub>5</sub>O<sub>9</sub><em>X(X</em>=Cl, Br) and SrB<sub>4</sub>O<sub>7</sub>. Strontium borate phosphors are usually synthesized by traditional solid state reactions by using SrCO<sub>3</sub> and H<sub>3</sub>BO<sub>3</sub> as raw materials. However, less attention has been paid to the influence of synthesis route on the final performance of the products. In this work, SrB<sub>4</sub>O<sub>7</sub>[DK(]∶[DK)]Eu phosphors were prepared using hydrated strontium borates(SrB<sub>2</sub>O<sub>4</sub>·4H<sub>2</sub>O and SrB<sub>6</sub>O<sub>10</sub>·5H<sub>2</sub>O) as raw materials. The effect of doping concentration and post-calcining temperature on the luminescence properties was studied. It was found that Eu ions with two oxidation states (+2 and +3) coexist in the SrB<sub>4</sub>O<sub>7</sub> host. The emission spectrum shows that the main emission peak located at 367 nm, which is attributed to Eu<sup>2+</sup> ions transition from 4f<sup>6</sup>5d to 4f<sup>7</sup>(<sup>8</sup>S<sub>7/2</sub>). The emission peaks of Eu<sup>3+</sup> ions located at 588, 600, 614, 651 and 700 nm corresponding to the transitions <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>0</sub>, <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>1</sub>, <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>, <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>3</sub>, <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>4</sub> respectively. Among them, the dominant emission is the electric-dipole transition <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>, indicating that the Eu<sup>3+</sup> ion occupies asymmetrical center in lattice. <br>The emitting intensity mainly depends on the amount of luminescence center which is relate to the doping concentration. The emitting intensity increases to a maximum with the increment of doping concentration, and then it decreases because of concentration quenching. When the Eu concentration is about 2%, the maximum of emitting intensity occurs. Post-calcining temperature influences on the chemical structure form of resultant powder. SrB<sub>2</sub>O<sub>4</sub>, SrB<sub>6</sub>O<sub>7</sub> and SrB<sub>4</sub>O<sub>7</sub> are formed when the post-calcining temperature is lower than 900 ℃. In these borates, SrB<sub>2</sub>O<sub>4</sub> contains only triangular BO<sub>3</sub> groups, SrB<sub>4</sub>O<sub>7</sub> contains only tetrahedral BO<sub>4</sub> groups, and SrB<sub>6</sub>O<sub>10</sub> contains both the BO<sub>3</sub> and BO<sub>4</sub> groups. As the temperature elevates, the proportion of SrB<sub>4</sub>O<sub>7</sub> increases and the single phase of SrB<sub>4</sub>O<sub>7</sub> can be obtained at 900 ℃. As a fact that the BO<sub>4</sub> groups can stabilize the divalent rare-earth ions to avoid oxidation, so that more Eu<sup>3+</sup> ions can be reduced to be Eu<sup>2+</sup> ions and the emission intensity would increase. It was also found that the emission intensity from the sample synthesized using hydrated borates is higher than that from the sample synthesized by traditional route.关键词：strontium borate;high-temperature solid state reaction;hydrated strontium borate;luminescent properties91|102|6更新时间：2020-08-12
- 摘要：Rare-earth doped borate phosphor has the advantage of low synthesis temperature, so it is suffered much of recognition in recent decades years. Ba<em>Ln</em>B<sub>9</sub>O<sub>16</sub> (<em>Ln</em>=La-Lu, Y) is a fine borate host, which can gained different phosphors by doping of different ions (Ce, Dy, Eu, Tb, Mn). For the before time investigation of borate phosphor, solid-state method was used for preparing, the fabrication temperature is about 1 000 ℃, and more the phenomenon of agglomeration is very grave. We synthesized a Eu<sup>3+</sup> doped boron-containing phosphor having a formula of BaGd<sub>1-<em>x</em></sub>Eu<sub><</sub>em>x</em>B<sub>9</sub>O<sub>16</sub> by sol-gel method, decreasing the crystallized temperature and avoiding the grave agglomeration.<br>Using Eu<sub>2</sub>O<sub>3</sub>, Gd<sub>2</sub>O<sub>3</sub>, boracic acid, barium carbonate acid as starting materials and citric acid as complexing agent, sol-gel method was used to prepare BaGd<sub>1-<em>x</em></sub>Eu<sub><em>x</em></sub>B<sub>9</sub>O<sub>16</sub> red phosphor. The influence of preparing condition was discussed, and their structure and luminescence property were characterized by X-ray diffraction (XRD) analysis and fluorescence spectrometry. The investigation showed that the sample can be crystallized under 850 ℃, and gained better crystallized production at 900 ℃. Considering to the luminescence intensity for the samples prepared at different crystallization temperature, BaGd<sub>1-<em>x</em></sub>Eu<sub><em>x</em></sub>B<sub>9</sub>O<sub>16</sub> phosphor can get better luminescence intensity and better purity.<p/>The investigation showed that there is huge quenching concentration of Eu<sup>3+</sup> in BaGd<sub>1-<em>x</em></sub>Eu<sub><em>x</em></sub>B<sub>9</sub>O<sub>16</sub>. Its about 90%. For the borate synthesis, boracic acid can be volatilization at high temperature, so 15% excessive boracic was necessary. The investigation found that the phosphor can be excitated by 264, 394, 465, 534 nm; they are assigned to Eu—O energy transfer, <sup>7</sup>F<sub>0</sub>→<sup>5</sup>L<sub>6</sub>, <sup>7</sup>F<sub>0</sub>-<sup>5</sup>D<sub>2</sub>, <sup>7</sup>F<sub>0</sub>-<sup>5</sup>D<sub>1</sub> transitions, respectively. The samples can emit out characteristic red light of Eu<sup>3+</sup> with the main peak of 614 nm, which is assigned to <sup>5</sup>D<sub>0</sub>-<sup>7</sup>F<sub>2</sub> transition. The energy transfer between Gd<sup>3+</sup> and Eu<sup>3+</sup> exist in this phosphor. Different from the phosphors prepared by solid-state method, the highest excitation position is not from energy transfer, it comes from f-f transition which located at 394 nm. Thats suitable to white LED that can give the excitation of purple ray.关键词：red phosphors;borate;sol-gel method91|128|1更新时间：2020-08-12
- 摘要：The upconversion (UC) processes of infrared light to visible light of rare earth ions doped different hosts have been investigated extensively, due to their potential applications in some fields, such as solid-state lasers, display, communications, and so on. The recent researches emerging at the intersection of nanotech-nology and biotechnology are opening up a new period for the development of UC. As known, the controlled fabrication of a host with aimed structure is important for enhancing the upconversion efficiency, because the phonon energy of the host can affect the probabilities of non-radiative decay and the energy transfer. Therefore, it is necessary to choose a lattice with much lower phonon energy, which is benefit to the upconversion luminescence. Rare earth-doped hexagonal sodium yttrium fluoride (NaYF<sub>4</sub>) is a good host, which is known to be a very efficient near-infrared to visible upconverter. The hexagonal NaYF<sub>4</sub> has low phonon energy. The structure of hexagonal phase gives rise to controversy about the cation sites and distribution. The trivalent thulium (Tm<sup>3+</sup>) is an ideal candidate for single wavelength NIR upconversion due to its ladder of nearly equally spaced energy levels that are multiples of the <sup>1</sup>G<sub>4</sub>→<sup>3</sup>H<sub>6</sub> transition. The development of compact blue lasers based on Tm<sup>3+</sup> upconversion processes is nowadays widely studied mainly due to the potential of high perfor-mance OEM applications, such as biomedical and analytical instrumentation, display, photoprinting. In thu-lium doped media, the efficiency of this process is very low, but it was noticed that the mechanism could be made one or two orders of magnitude more efficient by using ytterbium(Yb<sup>3+</sup>). In this paper, trivalent thu-lium (Tm<sup>3+</sup>) and yttebium (Yb<sup>3+</sup>) ions codoped NaYF<sub>4</sub> were synthesized by co-precipitation method. The concentration of Tm<sup>3+</sup> and Yb<sup>3+</sup> are 0.01%, 0.1%, respectively. The absorption spectrum of NaYF<sub>4</sub>∶Tm<sup>3+</sup>,Yb<sup>3+</sup> from 300 to 1 100 nm was measured at room temperature. The upconversion emission was observed when excited by 798 nm. The green and blue upconversion emission spectra were measured. Based on the experimental results the possible upconversion mechanism was analyzed. The main mechanism is the in-direct sensitization of Tm<sup>3+</sup> and Yb<sup>3+</sup>. The blue emitting light results from the transition of <sup>1</sup>G<sub>4</sub>→<sup>3</sup>H<sub>6</sub> of Tm<sup>3+</sup>, green emitting light is from the transition of <sup>1</sup>D<sub>2</sub> →<sup>3</sup>F<sub>4</sub> of Tm<sup>3+</sup>. To our knowledge, there have not been similar works published domestically and abroad. The structural properties of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that NaYF<sub>4</sub>∶Tm<sup>3+</sup>, Yb<sup>3+</sup> prepared by co-precipitation method exhibits hexagonal crystal phase.98|79|5更新时间：2020-08-12
- 摘要：We used finite element method to simulate affecting factors and distribution of quaternary AlGaInP LED's output efficiency of light with transparent electrode, and found that the thickness of window layer and size of the chip have important impact on them. With thickness increasing, the top surfaces output efficiency of light decreases a little, but the sidess output efficiency of light increases a lot, so the overall output efficiency of light presents rises a trend; and as increasing the thickness of window layer, the chips highest output efficiency of light distribution area moves to the center from four right angle areas of the chip. But with the size of the chip increasing, and changing in the opposite, the surface's output efficiency of light increases a little, and the sides's output efficiency of light decreases a lot, so the overall output efficiency of light presents a fall trend. After that, we simulated the light extraction efficiency of the general production chip, optimized the opaque electrode shapes at the guidance of this and optimized the width of the electrode further. Finally, the output efficiency of light can rise to more than six percentage of the traditional round electrode's.关键词：AlGaInP LED;output efficiency of light;electrode shape;finite element method141|175|2更新时间：2020-08-12
- 摘要：Self-assembled InAs quantum dots (QDs) capping with the InGaAs layer of the graded component are grown by molecular beam epitaxy (MBE) on GaAs (001). Surface structure, morphology and optical properties of QDs were studied by atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). The insertion of InGaAs layer enhances the quality of epitaxial layer, relaxes the stress of InAs quantum dots, changes the energy level of QDs and suppress the component segregation of indium from the quantum dots. Characteristic of devices were studied byphotocurrent spectra(PC) and volt-ampere characteristic curves. Wavelength red-shift of QDs device with InGaAs graded composition layer was determined by PL and PC curves.关键词：InAs quantum dots;InGaAs graded component layer;photoluminescence;molecular beam epitaxy;infrared detector device108|153|2更新时间：2020-08-12
- 摘要：Self-assembled InAs quantum dots (QDs) capping with the InGaAs layer of the graded component are grown by molecular beam epitaxy (MBE) on GaAs (001). Surface structure, morphology and optical properties of QDs were studied by atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). The insertion of InGaAs layer enhances the quality of epitaxial layer, relaxes the stress of InAs quantum dots, changes the energy level of QDs and suppress the component segregation of indium from the quantum dots. Characteristic of devices were studied byphotocurrent spectra(PC) and volt-ampere characteristic curves. Wavelength red-shift of QDs device with InGaAs graded composition layer was determined by PL and PC curves.87|128|0更新时间：2020-08-12
- 摘要：Silicon carbide (SiC) is known for its wide-band-gap electronic structure as well as excellent thermal and mechanical properties, thus is potentially useful for applications in high-temperature electronics and short-wavelength optics. However, applications of SiC in optical devices are limited by its indirect band gap nature, which results in very low light emission efficiency. In this paper, SiC nanorods were synthesized via catalyst-assistant crystallization of amorphous silicon carbonitride. And an intensive sharp photoluminescence at 378 nm and a weak broad emission band from 450 nm to 600 nm from SiC nanorods were observed at room temperature. The SEM image revealed that the SiC nanorods are of 80~100 nm in diameter and several micrometers in length. The TEM image showed that the nanorods contain a fairly large amount of sandwich structures. In order to confirm the structure of SiC nanorods, the XRD pattern and the micro-Raman spectra were employed. And the XRD pattern demonstrated that the nanorode consists of 3C-SiC as a sole type of crystalline with a plenty of stack fault, and no trace indicates a 6H-SiC polytypes. However the micro-Raman spectra give three scattering peaks at 508, 787 and 967 cm<sup>-1</sup>. Using Lorentz peak fitting, we found that it contains two series of peaks. One series of peaks were at 794 and 971 cm<sup>-1</sup>, corresponding to 3C-SiC. The other are at 508, 760, 783 and 964 cm<sup>-1</sup>, corresponding to 6H-SiC. So the results of XRD and Raman indicated that the sandwich structures are assembled by 6H-SiC and 3C-SiC. And the intensive sharp photoluminescence at 378 nm and a weak broad emission band from 450 nm to 600 nm might origin from 6H-SiC and 3C-SiC, respectively. The nanorods,which could possibly be assembled into nanostructures capable with strong ultra-violet light emitting, would be useful for short wavelength nanodevices.关键词：SiC;nanorod;sandwich structure;photoluminescence89|107|0更新时间：2020-08-12
- 摘要：Since the temperature has a great effect on emission wavelength of semiconductor laser device, constant temperature control is necessary to the situation which require high wavelength stabilization. In view of temperature error in constant temperature control of semiconductor laser by means of temperature sensor, a new method taking pn junction of laser diode (LD) itself as temperature detector to achieve the goal of constant temperature was proposed. The drive circuit of semiconductor refrigerator was designed also. This method makes use of the temperature sensitive characteristic of pn junction to test the temperature of pn junction through its terminal voltage. The experiment results showed that the temperature error caused by temperature gradient is eliminated; the experiment speed is increased; the overshoot value is reduced distinctly; and the static error and fluctuation were also eliminated.关键词：laser diode (LD);temperature detecting;temperature measurement by pn junction;semiconductor refrigeration110|119|3更新时间：2020-08-12
- 摘要：The phosphorous powders of nanocrystalline Gd<sub>2</sub>O<sub>3</sub>∶Eu<sup>3+</sup> were prepared by co-precipitation method. The room temperature sharp characteristic emissions of Eu<sup>3+</sup> ions were observed for the samples sintered under different temperatures and doped concentrations. The crystalline phases and luminescent properties of the samples were studied. The results showed that there exist different crystalline phases in the samples which were sintered at different temperature region from 800 ℃ to 1 300 ℃. The cubic phase was observed when the samples were sintered in the temperature region 800~1 300 ℃, and the cubic-monoclinic mixture phases were observed when the sintering temperature was 1 400 ℃. The effect of the Eu<sup>3+</sup> doping concentration on the fluorescence emission intensity was discussed. The optimum doped concentration for the luminescence intensity of Eu<sup>3+</sup> is determined to be 4% for the cubic structure samples. The optimum post-treatment temperature for obtaining the most intense emission is determined to be 800 ℃ for the cubic structure. Effective charge-transfer excitation and the energy transfer from the host and Gd<sup>3+</sup> to Eu<sup>3+</sup> were observed. The excitation spectrum is composed of three components, namely, the charge transfer band, intra 4f-configuration transitions of Eu<sup>3+</sup>, and the excitation spectrum of Gd<sup>3+</sup>.152|91|3更新时间：2020-08-12
- 摘要：Europium (Ⅲ)-doped yttrium oxide (Y2O3∶Eu3+) nanoparticles and nanorods were prepared by a novel combination approach, microemulsion-microwave heating. X-ray diffraction (XRD) analysis confirmed the formation of Y2O3∶Eu3+ phase. TEM results indicated that the synthesized samples show olive-ball-like morphology with 20~100 nm size or nanorod morphology about 30~50 nm in width and 200~300 nm in length. The nano-Y2O3∶Eu3+ samples emit much strong red light due to the 5D0-7F2 transitions of Eu3+ ions under near UV excitation, especially around 254 nm. The key excitation band at around 254 nm was originated from the Eu3+-O2- charge transfer. The PL intensity increases along with the increase in the particle size and the ratio of water to surfactant ω0.The fluorescence decay time of the Y2O3∶Eu3+ nanorod is about 2.03 ms. The I-V curve of cathodoluminescence for the Y2O3∶Eu3+ nanorod deposited on ITO glass showed that the startup voltage was only about 1 300 V.关键词：Y2O3∶Eu3+ nanorod;microemulsion-microwave heating;photoluminescence120|78|1更新时间：2020-08-12
- 摘要：Nanocrystals of up-conversion phosphor Er<sup>3+</sup>,Tm<sup>3+</sup> and Yb<sup>3+</sup> co-doped NaYF<sub>4</sub> were prepared by hydrothermal method in the prescence of complexing agent EDTA. Under 980 nm diode laser exciting, the impact of different concentration of Er<sup>3+</sup> ion on the up-conversion luminescence intensity was discussed.<br>
The samples were characterized by transmission electron microscopy and X-ray diffraction, the results showed that hexagonal nanocrystal NaYF<sub>4</sub>:Er<sup>3+</sup>,Tm<sup>3+</sup> and Yb<sup>3+</sup> was prepared by hydrothermal method. According to the law of luminescence intensity versus excitation power, the 474 nm blue emission, 525 nm and 539 nm green emission, 650 nm red emission are all due to double photon process, while the 408 nm violet emission is a three-photon process. The up-conversion mechanism and processes were also analyzed.116|48|3更新时间：2020-08-12 - 摘要：In this paper, SiO/SiO<sub>2</sub> superlattices samples were prepared on Si substrates by electron beam evaporation, and the thicknesses of SiO layers are 2 nm and 4 nm, 4 nm for all the SiO<sub>2</sub> layers. The samples were annealed in nitrogen atmosphere at high temperature subsequently. And then,Ce<sup>3+</sup> with a dose of 2.0×10<sup>14</sup> cm<sup>-2</sup> and 2.0×10<sup>15</sup> cm<sup>-2</sup> respectively was implanted into these samples with formed Si nanocrystals. After Ce<sup>3+</sup> doped, the samples were re-annealing at 600 ℃. The photoluminescence (PL) spectra were observed by the fluorescence spectrometry. The PL spectra showed that the PL intensities of samples were not only dependent on the re-annealing temperature and the dose of Ce<sup>3+</sup>, but also dependent on the size of nc-Si. The experiment results proved that when the size of nc-Si is 4 nm; the effect of energy transfer between Ce<sup>3+</sup> and nc-Si is more distinct.98|98|0更新时间：2020-08-12
- 摘要：Eu-doped SiO<sub>2</sub> matrix xerogels were prepared by sol-gel process. The samples were characterized with photoluminescence spectrum, transmission electron microscope (TEM), scanning electron microscope (SEM) and infrared absorption(IR) spectrum<em> etc.</em> The influence of annealing temperature on luminescent properties of the xerogels as well as influence of Eu<sup>3+</sup>, Eu<sup>2+</sup> doped ions on the luminescence of the the xerogels were presented. The mechanism of luminescence was studied. For the uniform doping samples, particle size was about 50~80 nm. The network structure of the matrix was changed because of boron(B) doping. Excited at 258 nm, with the increase of annealing temperature, the intensity of the red light emission at first enhanced, and then weakening. The red luminescent intensity of the sample annealed at 800 ℃ was the strongest. The spectral peaks are at 576 nm(<sup>5</sup>D<sub>0</sub> →<sup>7</sup>F<sub>0</sub>), 620 nm(<sup>5</sup>D<sub>0</sub> →<sup>7</sup>F<sub>2</sub>)and 658 nm(<sup>5</sup>D<sub>0</sub> →<sup>7</sup>F<sub>3</sub>), the strong red Eu<sup>3+</sup>emission of the samples centered at 620 nm was due to the transitions of <sup>5</sup>D<sub>0</sub> →<sup>7</sup>F<sub>2</sub> of Eu<sup>3+</sup>. Further, this detailed to B into the matrix, formed Si—O—B bonds, leading to Eu<sup>3+</sup> ions coordination environment with the lower symmetry, which is beneficial to the characteristic emission of Eu<sup>3+</sup>.In the presence of Al<sup>3+</sup>and excited at 271 nm, the blue luminescent intensity of the sample annealed at 850 ℃ reached the strongest, a strong blue Eu<sup>2+</sup> emission band centered at 400~500 nm was observed, which were due to the transitions of 5d→4f of Eu<sup>2+</sup>. The Al<sup>3+</sup> ions can increase the electron donation ability of oxygen in AlO<sup>-</sup><sub>4</sub> tetrahedron around Eu<sup>3+</sup> and reduced Eu<sup>3+</sup> to Eu<sup>2+</sup> . During the annealing process the rare earth ions may imigrate and form clusters. Therefore, the red emission of Eu<sup>3+</sup> and the blue emission of Eu<sup>2+</sup> were obviously reduced as annealing temperature is up to 900 ℃.107|137|2更新时间：2020-08-12
- 摘要：Rare earth complex materials have been widely used in cathodoluminescent display phosphor screens, lasers and lamps because their photoluminescence (PL) exhibits high quantum efficiencies and very sharp spectral bands. The luminescence process of the rare earth complex is as follows:the electrons in excited single state of the ligand move to the triplet state by intrasystem relaxation process, followed by the energy transfers from the triplet state of the ligand to the nearest resonance level of the rare earth ion.In the luminescence process, the single state and triplet state can only be used.Theoretically, the internal quantum efficiency can reach 100％, which is four times than that of other fluorescent materials.When europium ion chelates with some organic ligands, such as benzoic acid(BA), the emissions of rare earth Eu3+ ion exhibits highly pure red color and strong luminescence intensity. The intensity of sensitized luminescence of central lanthanide ions in a rare earth organic chelate depends on three factors.Firstly, the suitability of the energy gap between the excited triplet energy level of the ligands and the lowest excited energy level of rare earth ions. Secondly, the rigidity and planarity of the structure of the chelate molecule.Thirdly, the existence of a suitable secondary ligand which may increase the rigidity and the stability of the chelate molecule.In this paper, 1,10-phenanthroline (phen) derivative, 2-phenyl-imidazo [4,5-f] 1, 10-phenanthroline (PIP) were synthesized.With benzoic acid(BA) as the first ligand and PIP as the secondary ligand, a new ternary organic europium complex Eu(BA)3PIP was prepared.In the same condition, with the same first ligand and phen as the secondary ligand, Eu(BA)3phen was also prepared. The structures and compositions of the ligand PIP, Eu(BA)3PIP and Eu(BA)3phen were confirmed by elemental analysis, IR spectra, TG analyses, the fluorescence properties [JP2]of the two complexes were also studied. Elemental analysis demonstrates that the compositions of the ternary[JP] complexes are PIP , Eu(BA)3PIP and Eu(BA)3phen. IR spectra indicate that rare earth Eu3+ ion is coordinated with six oxygen atoms of three benzoic acid ligands and two nitrogen atoms of the second ligand.The emission spectra demonstrate that two kinds of ternary organic europium complex exhibit characteristic fluorescence of rare earth Eu3+ and the second ligand PIP has larger conjugation system, and under UV excitation, energy absorbed by the ligands in the complex can be transfed to the rare earth Eu3+ ion, so that it can emit characteristic luminescence of Eu3+, and the luminescence intensity of Eu(BA)3PIP is obviously higher than that of Eu(BA)3phen. The luminescence of complex was greatly sensitized by appropriate secondary ligand. TG analyses show that the thermal decomposition temperature of Eu(BA)3PIP are higher than that of Eu(BA)3phen. Thus the secondary ligand of 2-phenyl-imidazo [4,5-f] 1, 10-phenanthroline(PIP) obviously enhanced the fluorescent intensity of Eu3+and the thermal stability of europium complex. So, the new ternary organic europium complex of Eu(BA)3PIP is an excellent red-emitting material.关键词：synthesis;rare earth Eu3+;ternary complex;structure;luminescence property105|63|1更新时间：2020-08-12
- 摘要：In recent years, there has been increasing interest in the fabrication of the ordered fine structure using the naturally occurring self-ordered structures because of their potential utilization in the development of micromechanical, electronic and optoelectronic devices. The porous anodic alumina (PAA) formed by electrochemical oxidation has a fine structure with a nanohole array, and the radius of the pores can be controlled in the range of 1.5 to 500 nm by changing the preparation conditions. The PAA has recently attracted increasing attention as a host by introducing a guest.In this paper, Cu was implanted into the pores of PAA by means of electroplating, and the Cu/PAA film was obtained. With such metallic array, the alumina films exhibit optical polarization properties. The experiment results indicated that the polarization properties of Cu/PAA film depend on electroplating conditions. To a certain extent, with the increase of electroplating time and current density, the extinction ratio of Cu/PAA film can be improved; the temperature of electroplating solution is an important factor to influence on the extinction ratio, because a higher extinction ratio can be obtained at a smaller density and a higher temperature. So, a micro-polarizer can be achieved by optimizing electroplating conditions. With the simple technique, the controlled size and the convenience for industrialization, the Cu/PAA film prepared by electrochemical oxidation has extensive prospects in optical telecommunication.关键词：porous anodic alumina;electroplating;micropolarizer;extinction ratio102|181|0更新时间：2020-08-12
- 摘要：Laser remote sensing of the underwater sound field is more advanced detection technology for underwater object search, however, the sensitivity of the detection system had not been analyzed. This article analyzed three laser remote sensing methods for underwater sound field, and then studied the surface microwave formed from underwater sound field. It was obtained through the theoretical calculation that the minimum detection limit of amplitude was 0.424 4 mm for surface microwave. By analyzing the relationship between the minimum detection limit of amplitude, the height of sender and the aperture of receiver, it was understood for the theoretical basis of influence factors for the detection of underwater sound field, also provided for the basic idea for improving sensitivity.关键词：detection of underwater sound field;laser remote sensing;the minimum detection limit of amplitude;direct detection100|157|0更新时间：2020-08-12
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