最新刊期
卷 29 ， 期 5 ， 2008
- 摘要：Snell's law reveals the propagation and refraction properties of the light when it passes through the interface composed by twomedia with different optical constants.It is the foundation of modern physical and geometrical optics.The effort to realize a perfect lens is trying to find the material with a negative refractive index,which has notyet been found in the natural material in pastyears.In this work,we have fabricated a series of noble-metal-based film samples (Au and Ag) with different incident angles.We quantitatively measured the refraction of the light passing through the metal/air interface,and observed that the refraction can change from negative to positive in the visible range at the simplest naturalmetal/air interface.The mechanisms for causing the negative refraction have been carefully discussed and analyzed,and are notattributed to the effects,such as the plasmon resonance,the negative permeability,the Goos-Hanchen shift and so on.We hope,therefore,the results given in this work will stimulate people to understand more of the physicalorigin of the negative refraction happened in themetal-based artificial materials,and will help its application in the photonics material and device design and fabrication in the future.关键词：Snell law;refractive index;metal optics;plasm frequency;group velocity118|87|1更新时间：2020-08-12
- 摘要：Four solid quaternary complexes of light rare earth perchlorate with diphenyl sulfoxide (L) and benzoic acid (L') have been synthesized and characterized.By elemental analysis,TGA-DTAand themolar conductivities in acetone solution studies,the composition of the complexeswere suggested as [REL5L'(ClO4)](ClO4) (RE=La,Pr,Nd,Eu;L=C6H5SOC6H5,L'=C6H5COO-).As shown in IRspectra,the absorption band associated with the S-Ostretching modes in the first ligand diphenyl sulfoxide appears at 1037 cm-1,while the absorption bands in the complexes appear between 987 cm-1 and 989 cm-1.Ashift of the S-Ostretching frequency towards lowerwave number by about 50 cm-1 suggests that rare earth ions are bonded with an oxygen atom in sulfoxyl group.In the second ligand benzoate,the absorption band associated with νas(COO-)appears at 1550 cm-1,νs(COO-) appears at 1416 cm-1.The value of Δn[νas(COO-)-νs(COO-)] is 134 cm-1.Ashift of νas(COO-) frequency in complexes towards higherwave number,while a shift of νs(COO-) frequency in complexes towards lower wave number.What's more,the value of Δn[νas(COO-)-νs(COO-)] in complexes is higher than that of Δn[νas(COO-)-νs(COO-)] in sodium benzoate.This showed that benzoate (L') bonded with RE3+ ions by one oxygen atom in carboxylgroupwhich coordinate as an unidentate group.One of two perchlorates (ClO4-) is coordinated with RE3+ while another is not.Fluorescent spectra of Eu3+ complex showed thatquaternary complexes have stronger fluorescence than the binary one whose ligand is diphenyl sulfoxide,(the fluorescence intensity of Eu3+ complex increased by 469%).Phosphorescent spectra of two ligands showed that the lower limit of the triplet state with benzoic acid was overlapped by the upper limit with diphenyl sulfoxide,the energy level range of triplet state was extended.As a result,matching extent of triplet state of ligandswith excited state of the rare earths have been increased by coordination of the second ligand benzoic acid,the transmit efficiency also have been increased.Attributed to the addition of the second ligand,the symmetry of the complexes always have been decreased,as a result,the fluorescence intensitywas increased.关键词：light rare earth quaternary complexes;diphenyl sulfoxide;benzoic acid;fluorescence;phosphorescent spectr103|68|4更新时间：2020-08-12
- 摘要：In this communication,the poly(vinylidene difluoride) (PVDF)/(Y0.97Eu0.03)2O3 rare-earth nanocompositeswere prepared by a facile co-precipitation method with the aid of ultrasonic technique.The cross sections of the nanocomposite were observed by scanning electron microscopy (SEM),and the luminescent properties of the nanocompositeswere studied by fluorescence spectroscopy.The SEM results showed that the (Y0.97Eu0.03)2O3 nanoparticles were dispersed in PVDF matrix as some aggregateswith the sizes between 50 nm~2μm when themass fraction of (Y0.97Eu0.03)2O3 was between 1% and 5%;while the (Y0.97Eu0.03)2O3 particles were better dispersed in the matrix when the (Y0.97Eu0.03)2O3 mass fraction was lower than 1%.The lumine scence spectra showed a characteristic red-emitting of PVDF/(Y0.97Eu0.03)2O3 nanocomposites at 612 nm,corresponding to the intrinsic luminescence of the Eu3+ ion in (Y0.97Eu0.03)2O3nanoparticles.The prepared rare-earth nanocomposites with unique optical characteristicmay be used as opticalmaterials in the future.关键词：poly(vinylidene difluoride) (PVDF);(Y0.97Eu0.03)2O3;nanocomposite;luminescent property101|57|1更新时间：2020-08-12
- 摘要：300 nm Eu(DBM)3Phen/SiO2 colloidal hybrid spheres were synthesized by modified Stöber method.The silica spheres were self-assembled into 3D ordered crystal structure with 5 mm thick and over relative large areas (12 cm2) via sedimentation.The scanning electronmicros copy (SEM) images indicate that the cubic-close-packed structure extends almostall of the layers along the direction perpendicular to the surface of the bottom of the beakerand the close-packed order extends throughout the colloidal crystal.Furthermore,elemental analysis of silica spheres by EDAX establishes that the fluorescent molecules contained in the SiO2 colloidal spheres.Under 355 nm continuous excitation,the ordered structure exhibits characteristic emission of trivalent europiumions.关键词：Eu(DBM)3Phen/SiO2;self-assembly;sedimentation;3D ordered structur108|77|1更新时间：2020-08-12
- 摘要：GaN-based quantum wells are the core structure of optoelectronic devices such as light-emitting diodes,laser diodes.Our experiments show that,In0.2Ga0.8N/GaN ternary alloys quantum wells and Al0.15In0.01Ga0.84N/In0.2Ga0.8N quaternary alloy quantum wells,two different quantum well structures for laser diode,have significant differences about the electrical properties and luminous efficiency.In this paper,we study onmicroscopic characteristics of these two differentquantum well structure.Through high-resolution X-ray diffraction,we got the satellite peaks of these two different alloys quantum wells by ω/2θ scanning.Using X-ray diffraction,we got the rocking curves by ω scanning of two kinds of MQW's symmetry face (002) and asymmetric face (101),(102),(103),(104),(105) and (201).Through atomic forcemicroscope,photolumine scence spectra and high resolution X-ray diffraction,it revealed the different nature of the macro factors of the In0.2Ga0.8N/GaNternary alloys and Al0.15In0.01Ga0.84N/In0.2Ga0.8N quaternary alloys.98|52|2更新时间：2020-08-12
- 摘要：The fabrication process of low temperature poly-Si(LTPS) TFT(Thin Film Transistor) can be simplified by p-type technology.In this paper,an improved shift register scheme is proposed,which only consists of p-type poly-Si TFTs.It can be integrated on the panel of AMOLED or AMLCD as a part of peripheral driving circuitry.The shift register is controlled by 6 clock signals and every unit is composed of 6 p-type poly-Si TFTs.In order to verify the correction of the proposed scheme,circuit simulation using HSPICE has been done.Utilizing the advantage of Korea on making poly-Si TFT,we have already fabricated 96×3×128 AMOLED by using the proposed design.关键词：shift register;p-type technology;poly-SiTFT;AMOLED;HSPICE simulation111|100|0更新时间：2020-08-12
- 摘要：Three series silicate phosphors(A:(SrBa)3SiO5:0.024Ce3+,0.024Li+;B:Sr2.73M0.2SiO5:0.07Eu2+(M=Ba,Mg,Ca);C:(SrBa)3SiO5:xEu2+)were synthesized by solid reaction method.Their excitation and emission spectra were measured.There are two exitation peaks(351 nm and 418 nm,418 nm is stronger) for Ce3+-activated(Series A) silicate phosphors.With increasing the content of Ba ion,their emission peaks change to longer wavelength.Consequently,we can change its color then at the end adjust the CIE chromaticity and color rendering index of white-LED.Eu2+-activated(Series Band C) silicate phosphors have broad excitation bands from 350 nm to 450 nm.The emission peaks of Ce3+-activated silicate phosphors are 540～555 nm and shorter than Eu2+-activated silicate phosphors,while the emission peaks of Eu2+-activated silicate phosphors are at 570～583 nm.For the series B(Sr2.73M0.2SiO5:0.07Eu2+(M=Ba,Mg,Ca)),it's better when M=Ba.At the series C((SrBa)3SiO5:xEu2+),their emission peaks and FWHM change with no obvious rule.The emission peaks of Ba-doped Sr3SiO5:Ce3+,Li+ and Sr3SiO5:Eu2+ shifted to longer wavelength.Both of them can be used for packaging white-LED with NUV,UV and blue LED chip.关键词：white-LED;silicate;phospho111|79|6更新时间：2020-08-12
- 摘要：Nowadays,along with the maturity of the nUV technology,the project that nUV LED excite tricolor phosphor to make white light will be more noticeable.For the lack of phosphors matching the nUV LED chip,it is important significantly to explore this kind of phosphor.So,a new-style red phosphor excited by nUV LED is discussed in this paper.Since the band-gap of CdO(2.3 eV) is smaller than that of ZnO(3.3 eV),the band-gap of the material with Zn2+ as host can be narrowed by doping Cd2+.And by codoping Eu3+ and Li+,the red-light phosphor CdxZn1-xO:Eu3+,Li+ is produced.Eu3+-doped CdxZn1-xO phosphor was prepared by solid-state method at 1100℃ in atmosphere.The effect of Cd2+ doping on the luminescence and the excitation spectra of this phosphor has been analyzed.The XRD pattern of the sample shows that the phase of the sample is the simple ZnO phase,the doped ions lock-in Zn site or interstitial site.For the ion radius of Cd2+(0.097 nm) is larger than that of Zn2+(0.074 nm),when Cd2+ take place of the lattice of Zn2+,the lattice parameter is expanded.So the XRD peaks of Cd-doped ZnO shift to small angles compared with that of pure ZnO.The excitation spectra for 609 nm emission of CdxZn1-xO:Eu is measured at room temperature.The addition of the Cd2+ narrow the band-gap of the system,and by changing the concentration of Cd2+,the peak of the excitation spectra can be adjusted between380 nm and 410 nm.The excitation peak at 466 nm belongs to the 7F0-5D2 transition of Eu3+ ion,and the peak at 533 nm belongs to the 7F0-5D1 transition of Eu3+ ion.The luminescence of the sample is a broad-band emission at 520 nm,but the emission of Eu3+ is not detected when the samples were excited by 381,387,398 and 411 nm UV light.The results show that the energy-transfer between the host and Eu3+ is not available.In order to enhance the energy-transfer between the host and Eu3+,Li+ was co-doped as charge compensator.The emission of Eu3+ is detected in the emission spectra of the sample adulterating Li+ as charge compensator.The main peak of the emission spectra locates at 609 nm.It belongs to the 7F0-5D2 transition of Eu3+.For the ion radius of Li+ is very small,it's easy to enter into the crystal lattice of the host.The dopant enhances the energy-transfer between the host and Eu3+ and also enhances the luminescence intensity.The excitation range of the sample from 380 nm to 410 nm covers the emission wavelength of the ultraviolet LED chip.The intensity of emission was enhanced when Li+ is introduced into the system,and the photolum inescence of the phosphor is red.So this luminance phosphor is a possible kind of red fluorescent powder applying to white LED.关键词：CdxZn1-xO:Eu3+;rare earth;white-light LED;phosphor107|64|0更新时间：2020-08-12
- 摘要：Organic light emitting diodes(OLEDs) have been extensively investigated and significantly improved over the past two decades.The mechanism for electroluminescent(EL) phenomenon involves in the injection of holes from anode and electrons from cathode under forward bias voltage,then the hole-electron forming the exciton,and light emission through the radiative recombination of excitons.Due to the superior achieved performance,OLEDs are potential candidate not only for next generation displays,but also for solid state lighting application which requires high efficiency and low operating voltage.Through proper material design/choice and device fabrication,various colors of bright luminance have been developed for use in singleor full-color application.Among various colors,white organic light-emitting diodes(WOLEDs) draw particular attention as their highly potential application in blacking,full color application,as well as in lighting purposes.So far,a variety of methods have been proposed to achieve a WOLED,such as(Ⅰ) a multilayer device with blue,green,and red emissive layers,(Ⅱ) a doped device with a host material and blue,green,and red fluorescence dyes,(Ⅲ) a single-emission-layer device with white emission material,(IV) excimer and exciplex emission,and(Ⅴ) stacked structure.About IV,white-light emission can be obtained from a bilayer device using two blue-emitting polymers,in which an exciplex emission at the bilayer interface occurs in addition to an emission from one of the emitter.In addition,finding a simple fabricating way to realize full-color OLEDs is also an important and imperative approach to reduce manufacturing cost in industrial production.In this work,OLEDs were fabricated with a simple structure of indium-tin-oxide(ITO)/poly(N-vinylcarbazole)(PVK):N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-diphenyl-4,4'-diamine(NPB)/2,9-dimenthyl-4,7-diphenyl-1,10-phenanthroline(BCP)/Mg:Ag by spin coating method,which used a blend of two blue-emitting materials of PVK and NPB with different weight ratios.The luminance-voltage and current density-voltage characteristics of devices were investigated,and differences between their performances were discussed.The results demonstrate that optimum device performance could be obtained by choosing the concentration proportion of PVK:NPB at 1:1.In EL spectra of the device,except for the emission of NPB,a new emission peak at 640 nm proposed to be electroplex that formed between PVK and NPB was observed.Also,the relative emission intensity of electroplex increased with enhanced electric field.The Commissions Internationale De L'Eclairage(CIE) coordinates of Device Care x=0.30,y=0.28 at 12 V,which obviously belongs to white light emission.关键词：organic light-emitting devices (OLEDs);PVK/NPB blend system;electroplex101|79|2更新时间：2020-08-12
- 摘要：A novel blue-light-emitting material of thiophenyl distyrylarylene,4,4'-bis(2-phenyl-2-(thiophen-2-yl)vinyl-1,1'-biphenyl was designed and synthesized.Its structure was determined by IR,1H NMR and elementary analysis.It's HOMO,LUMO and luminescence characteristic was studied by UV-V is absorption spectra,fluorescence spectra and cyclic voltammetry.The HOMO energy and LUMO energy of TPVBi is-5.55 eV and-2.67 eV,respectively.TPVBi emits blue fluorescence with a peak wavelength at 451 nm in solution and with a peak wavelength at 464 nm in film.Organic light-emitting-diode with a structure of ITO/CuPc(10 nm)/NPB(30 nm)/TPVBi(35 nm)/TPBi(35 nm)/Al(100 nm) was prepared and electrolum inescence properties were studied.The device exhibited a maximum luminance of up to 1782.3 cd/m2 at 19.5 V and a maximum efficiency of up to 1.73 cd/A at a current density of 15.69 mA/cm2.The CIE chromaticity coordinates of the light emitted from the device are x=0.25,y=0.40.关键词：thiophenyl distyrylarylene;blue-light-emittingmateria;lorganic electrolum inescence118|76|0更新时间：2020-08-12
- 摘要：Pentacene is one of the most intensively studied systems among various organic semiconductors,for its relatively high field effect mobility and its ability to form ordered films.Nevertheless,pentacene suffers from the disadvantages of oxidative instability and,for display applications,a strong absorbance exists throughout the visible spectrum.Where photoinduced decomposition reactions could occur,this absorbance would make pentacene sensitive to most visible light.Compared to pentacene,there is an important small molecule semiconductor,that is thiophene-based materials exhibiting a variety of intraand intermolecular interactions-van der W aals interactions,weak hydrogen bandings,π-π stacking,sulfur-sulfur interactions-originating from the high polarizability of sulfur electrons in the thiophene rings.From the molecule structure,it can be analyzed that pentathienoacene(PTA) has high stability than pentacene owing to PTA's large band gap.These performances indicate PTA may have potential application in future organic electronics.However,the report on its application and basal physical characteristic obtained from experiment is few,and its theoretic research is much less.Quantum chemistry calculation can provide credible and valuable information for molecule study.In this paper,PTA molecule was calculated,including geometry model,infrared spectra,Raman spectra,HOMO-LUMO gap and the frontier molecular orbits by density function theory(DFT) for the first time,so the results can provide some reference informations for the future organic devices materials design theoretically.The infrared spectra and Raman spectra have been discussed and the spectra peaks of pentathienoacene were identified,the above datum on Raman spectra of PTA can provide the valuable reference for the experiment on PTA molecule identified.And at the same time,the HOMO-LUMO gap is gained:3.86 eV,which is very close to the experimental result.The five strongest allowable singlet excited states have been studied by TDDFT.The results indicate that all the energies of excited states were located in ultraviolet region,so PTA molecule is relatively stable under the visible light illumination because photoinduced decomposition reactions can not occur.The transition electron is diverted from carbon atom to sulfur atom,which can be seen through the frontier molecular orbits of pentathienoacene.Moreover,the formation of π-delocalized band leads to increase PTA molecule conductival.The results indicate that pentathienoacene is a new kind of organic semiconductor material and has perfect luminescence and electrical properties,especially,PTA has higher stability than pentacene.关键词：density function theory (DFT);pentathienoacene;infrared spectra;raman spectra;excited state113|99|0更新时间：2020-08-12
- 摘要：Five solid complexes of rare earth Eu3+ doped La3+,Gd3+,Y3+,Er3+ and five different proportion co-doped complexes(Eu3+:La3+) with 2-thiopheneacetic acid and o-phenanthroline have been synthesized and characterized.Elemental analysis,rare earth coordination titration and TG-DTA studies show that the complexes have the composition of Eu(TPAC)3Phen.The different dinuclear complexes are composed of Eu0.5RE0.5(TPAC)3Phen(RE3+=La3+,Gd3+,Y3+,Er3+);(EuxLay)(TPAC)3Phen(x:y=0.10:0.90;0.30:0.70;0.40:0.60;0.70:0.30;0.90:0.10).The molar conductivity indicates that all the complexes are nonelectrolyte;IR spectra and 1H NMR spectra show that 2-thiopheneacetic acid combined as the form of bridging dissymmetrical bidentate ligand,and the two nitrogen atoms in phen are also involved in the rare earth ion coordination for europium complex and its doped with La3+,Gd3+,Er3+ and Y3+ complexes.There are strong fluorescence intensity for all these complexes,it shows that the lowest excitation state energy level of Eu3+ ion with the triplet state energy level of the ligands match well each other.Its fluorescence intensity is enhanced after doping with La3+,Gd3+,Y3+.The sensitization actions from La3+,Gd3+,and Y3+ to Eu3+ ion are Y3+<Gd3+<La3+.But Er3+ make the fluorescence intensity of the europium complex weaken.We also find that as n(Eu):n(La)=1:1,the fluorescence intensity is the strongest in the complexes of(EuxLa1-x)(TPAC)3 Phen.5D0 energy level of Eu3+ is 17 250 cm-1,the triplet state energy of 2-thiopheneacetic acid and o-phenanthroline are 25 000 cm-1 and 22 123 cm-1,respectively.The triplet state energy of the two ligands are higher than the excitation energy of Eu3+ ion,thus it is possible that energy transfer from 2-thiopheneacetic acid and o-phenanthroline to Eu3+ through —COO—Eu—OOC— and —N—Eu—N— bonds.The absorbing energy of the ligands are effectively transferred to europium ion in the luminescence center,and producing a characterization spectrum.Some complexes of non-fluorescence rare earth can absorb the triplet energies of the ligands too,and then transfer them to Eu3+,in this way the fluorescence intensity was enhanced.If the transition energy of non-fluorescence rare earth complexes is lower than the 5D0 energy of Eu3+,the luminescence will be quenched.关键词：2-thiopheneacetic acid;o-phenanthroline;europium complex;fluorescenc106|71|3更新时间：2020-08-12
- 摘要：A luminum lactate has been gradually and widely used as important reagents and raw chemical material in various fields,such as daily chemical industry,industrial production,medicine,and life sciences,etc.Thus the amount of aluminum lactate production increases,therefore,it is of great importance to monitor aluminum lactate.The published analytical methods for Al determination can be categorized two kinds.One is the direct method and the other the derivatization-based method.The former methods include atomic absorption spectrometry,and inductive coupled plasma atomic emission spectrometry(ICP-AES),and the latter do spectrophotometry,resonance Rayleigh scattering(RRS) and fluorescence.Chemilum inescent(CL) methods have characteristic rapid assays,and good reproduction with simple instruments(no monochromator required),etc.However,there are few literatures in which Al was measured by CL method.It is a little cockamamie to use the indirect CL analysis such as aluminium chelates form and coupling reaction.Though the latest literatures directly on CL analysis of luminol system,the usage of it,are still limited because luminol is the CL reagent in alkaline solution.In an acidic medium,direct CL analysis of Al without derivatization has not been reported in the literature.In this work,the feasibility of direct dermination of acidic Al using flow injection CL system was studied for the first time,the kinetic curves of aluminum L-lactate-gold nanoparticles-acid potassium-permanganate,aluminum L-lactate-gold nanoparticles and aluminum L-lactate-acid potassium-permanganate systems were investigated.The CL signal was detected with a flow injection chemiluminescence system(Xian Ruimai Electronic Technology Co.,Ltd.,China)consisting of a model MPI-Bperistaltic pump,a mixing tee,a model MPI-B CL detector equipped with a glass coil(used as reaction coil and detection cell),a photomultiplier,and IBMcompatible microcomputer.it was found that aluminum L-lactate enhanced strongly the CL of gold nanoparticles-acid potassium-permanganate system.The activities of enhancement were related to the concentration of KMnO4,H2SO4 and Au,the pump speed and the channel of the flow injection CL system.On this basis,a novel flow injection method with enhanced chemiluminescent detection was deve-loped.It allows the detection of aluminum L-lactate in the range of 7.0×10-5～1.0×10-2 g·mL-1 with a detection limit of 1.04×10-6 g·mL-1(S/N=3).The relative standard deviation is 1.48% for the determination of 8.0×10-4 g·mL-1 aluminum L-lactate(n=11).The method has been successfully used to determine aluminum L-lactate contents in synthetical solutions and separate wastewaters with the recoveries of 95.8%～100.4% and the results obtained by this method were comparable with that by GB/T 6987.8-2001(National Standard of P.R.China).Finally,the CL kinetic curves and UV-visible absorption specta were studies and the CL enhancement mechanism has been proposed due to the quickened the reaction of aluminum L-lactate with gold nanoparticles and acid potassium-permanganate.关键词：aluminum L-lactate;gold nanoparticles;acidic potassium-permanganate;CL enhancement117|93|0更新时间：2020-08-12
- 摘要：Currently GaN based blue light emission diode(LED) has already been widely used in spotlight of cars,back light of mobile phones,outdoor displays,etc.As the market of its applications is rapidly enlarged,the reliability of GaN based LED becomes the top issure of wide concern.In order to improve the reliability of vertical GaN based blue LED on Si substrate,SiN passivation layer was deposited by PECVD on the chip of LED,stresses in different condition were carried out to both passivated and unpassivated chips and encapsulated LEDs,their optical and electrical properties were investigated.After the aging under the condition of 30 mA,85℃ for 24 hours,the average luminous decay for encapsulated LEDs without SiN layer was 11.41%,but 6.06% for passivated one,lower luminous decay of SiN passivated GaN based blue LED was also found at the aging condition of RT,30 mA,96 hours,this was never reported in previous dissertations.In the aging experiment of chips under the 500 mA,RT condition,higher reverse voltage of SiN passivated LED was found after aging compared with that without SiN layer,but no obvious improvement for ESD property.关键词：blue LED;GaN;Si substrate;SiN;passivation;luminous decay128|83|2更新时间：2020-08-12
- 摘要：Vertical-cavity surface-emitting lasers(VCSEL) have many advantages such as low threshold current and single mode operation,as well as easy to be fabricated in high-density arrays and low cost in manufacturing.VCSELs are used in many areas,for example,optical communications,optical interconnections,and optical signal processing.But in some applications,the polarization orientation is sensitive,such as optic recording and laser frequency doubling.It is necessary to control the polarization characteristics of VCSEL effectively.In fact,the reliable control of the polarization orientation of single devices with small emission window is realized through many methods,in which the most popular one is the sub-wavelength surface grating technique.But due to the existence of multi-transverse modes in high power VCSEL devices with large emission window,the polarization orientation changes from one basic state to the other orthogonal one depending on the input current and temperature.The temperature dependence of the polarization characteristics of a 980 nm bottom-emitting laser with 500 μm emitting aperture is investigated.The temperature changes from 298 K to 368 K with a increasing step of 5 K.It is not easy to directly measure the temperature of the active region,so the temperature of the heatsink is used to characterize the temperature of the active region.Apolari-zation beam splitter(PBS) element is used to split the two orthogonal polarization states into transmission wave and reflection wave,respectively.The output powers and center-wavelengths of these two orthogonal polarizations states are measured by using a semiconductor laser parameters test system.The temperature dependence of the output power of each polarization state is the same as that of the total output power of the device without the PBS.The center-wavelength difference between the two polarization states increases slowly with increasing temperature.When comparing the polarization behavior of both states,we find that the reflection state reaches threshold of lasing before the transmission state when the device is kept at a temperature below 328 K.But the output power in the transmission state rises quickly than that in the reflection state.At every temperature,there is a certain current where the powers in the two states are equal with increasing the current.With increasing the current further,the power in the transmission state is higher than that in the reflection state.And when the device is kept at a temperature above 328 K,there is no obvious alternation point between the two states,and the power in the transmission state is higher than that in the reflection state all the time.The reason may be that at low temperature and low current,the heat effect is not serious,the red shifts of the reflection wave and transmission wave are both small,but reflection one is a little more,so the reflection wave is closer to the center-wavelength of DBR.With increasing the current,the internal temperature of the device increases seriously,the red shift of reflection state increase faster than that of transmission state,so the transmission wave is closer to the center-wavelength of DBR.At high temperature the heat effect is serious,whatever at low current and high current,both of the red shifts are big,so the transmission wave is closer to DBRcenter-wavelength all the time.According to the detailed investigation on the polarization characteristics of large diameter VCSEL device,a method with an external resonator was proposed to realize a stable polarization orientation with a resonance length of about 0.45 mm.关键词：vertical cavity surface emitting laser (VCSEL);PBS;polarization basic state128|114|0更新时间：2020-08-12
- 摘要：InN materials have been attracting a lot of attention for its prominent application in electronic and optical devices,compared with GaN and AlN,InN has smaller effective mass and higher electron drift velocity.However,the growth difficulties due to low growth temperature and lack of lattice-matched substrate restricted the evolution of InN-based devices,more and more efforts are made in efficiently deposit InN films with better quality.InN films were synthesized on the(0001) sapphire substrates at different growth temperatures by metal organic chemical vapor deposition(MOCVD),the growth source materials are trimethy lindium(TMI),trimethy lgallium(TMG) and ammonia(NH3).The physical properties of the films were characterized by a series of measurements.We fully studied the characteristic of InN films by various methods,such as X-ray diffraction(XRD),atomic force microscope(AFM),X-ray photoelectron spectroscopy(XPS) and Raman measurements.It's well known that the growth temperature is one of the most important parameters in growth of InN films,so in our study,we focus our attention mainly on the effect of growth temperature.It was found that 600℃ is a suitable growth temperature for InN films,the suitable temperature can inhibit the surface segregation phenomenon of In on the surface of InN films.But at a lower or higher temperature it will lead to a surface segregation of In on the InN films.The crystalline quality and morphology of the surface for the sample without surface segregation have been improved compared with the samples with surface segregation.In addition,it was also found that the residual strain in InN films increased with increasing growth temperature by Raman analysis,the E2(high) model frequency shift toward high frequency with increasing growth temperature,and this shift is due to the presence of residual thermal strain in the InN film.When the growth temperature is lower,the residual thermal strain came into being due to the different thermal expand coefficient between the epitaxial-film and the sapphire substrate.The residual thermal strain is biaxial strain,which can be expressed as:εxx=(Tg-Tr)(αsub-αfilm),Tg,Tr are the growth and room temperature,αsub,αfilm are the thermal expand coefficient of sapphire substrate and InN film,respectively.The relation between E2(high) model frequency and residual thermal strain can be expressed as:ω=20εxx+479(cm-1),which fit from the result of Raman analysis,where ω is the E2(high) model frequency,and εxx is the residual biaxial thermal strain.关键词：In segregation;X-ray diffraction;atomic force microscope;X-ray photoelectron spectroscopy;Raman scatterin113|106|0更新时间：2020-08-12
- 摘要：The undoped ZnO and Nd-doped ZnO thin films were deposited on Si(111) substrate by radio frequency magnetron sputtering.The lattice structure and the surface morphology were analyzed by X-ray diffraction and atomic force microscope,respectively.The results indicate that owing to the lager radius of Nd atoms than Zn atoms the Nd were substitution atoms in the ZnO lattices.The Nd-doped ZnO thin films were nano-multi-crystal and the surface morphology were roughness since the deformation of Nd-doped ZnO lattices.The room temperature photoluminescence spectrum indicates that undoped ZnO thin films and Nd-doped ZnO thin films have strong purple band at 395 nm and weak green band at 495 nm.Because of the exciton recombination the purple peaks are narrower and stronger than that of the green peak.The weak green peaks come from the oxygen vacancy and the oxygen antisite of Zn defects in the films.We also found that the Nd-dopd has no effect on the emission peak position of the PLspectrum.Due to the charges number of the Nd3+ions are not equals to the Zn2+ ions,in order to keep the charge neutral of ZnO,the interstitial Zn atoms must exist as compensation acceptor impurity which comes from the substitution of Zn atoms in ZnO by Nd,meanwhile the density of exciton were also changed.Besides the luminosity of luminous peaks were also changed by the lattice deformation and the density change of ZnO.关键词：Nd-doped;ZnO thin films;radio frequency magnetron sputtering;photoluminescenc117|89|4更新时间：2020-08-12
- 摘要：ZnO epitaxial films with and without Au buffer layer were grown on Si(001) substrates by a home-made chemical vapor deposition(CVD) technique.The Au buffer layer was evaporated in a physical vapor deposition(PVD) equipment,and its thickness was about 300 nm.After that,the Au/Si(001) template was transferred to a home-made CVD system to grow ZnO epilayer.Zn and Oprecursors were element zinc(5N) and deionized water vapour respectively,and high-purity nitrogen gas(5N) was employed as a carrier gas.The reactor pressure was at atmospheric pressure.A 1 μm-thick ZnO buffer layer was firstly deposited on the Au/Si(001) template at 650℃,and annealed in situ at 800℃ for 10 min.Then the main layer was grown at 800℃ for 3 min.The thickness of ZnO main epilayer was about 6 μm.The crystal properties of the ZnO films are studied by X-ray diffraction(XRD) equipment.The ZnO film directly grown on Si(001) substrate is apparently polycrystalline.Besides the diffraction peaks of ZnO (002) and(004),there are many other peaks like ZnO (102),(103) etc.For the ZnO film with an Au buffer layer,the crystal quality is improved a lot.Although it is still polycrystalline,the ZnO film with an Au buffer layer is highly c-axis oriented.Optical microscope is used to observe the surface morphologies of the ZnO films.The size of the grains and smoothness of surface of the ZnO film with an Au buffer layer are much better than that of the opposite one.The optical pro-perties of ZnO films are examined by means of photoluminescence(PL) spectra excited by a 325 nm He-Cd laser at room temperature.There are the excitonic related near band edge(NBE) emission peaks in the ultraviolet region in both of samples.While the deep-level emission(DLE),which is usually defect-related,is difficult to observe in the spectra of both samples,which indicates that the two films have good optical qualities.It is interesting that the intensity of NEB peak of the ZnO film with an Au buffer layer is weaker than the one without Au buffer layer.The main reasons could be:(1)The intensity of NEB peak is related to the crystal quality of every single grains.For the ZnO film directly grown on Si(001) substrate,the crystal quality of the single grains may be better than the opposite one;(2)The confinement of the carriers is favor to the photoluminescence of the films.For the ZnO film without Au buffer layer,there are more grains to confine the carriers,so the intensity of NEB peak is much stronger;(3)The surface of the ZnO film without Au buffer layer is more rough,so the picking-up light efficiency is much higher,then the light is much easier to give out.Further studies are in progress to investigate this phenomenon.关键词：ZnO epitaxial film;Au buffer layer;CVD105|97|2更新时间：2020-08-12
- 摘要：The application of UV detector in commerce and military are mainly focus on photomultiplier tube and UV detector based on silicon at present.However,the ponderosity,large energy consumption,and the attachment of the filters have certain limitation on the application of the photomultiplier tube as the UV detector.Recently,more attentions were paid on the solid wide gap semiconductor UV detector,especially for the potential application in solar blind region(220 nm to 280 nm) for the detection of the missile plume.The realization of GaN-based pn junction detector accelerated the development of UV detector in solar blind region.But the lack of the lattice mismatch substrate for the growth of GaN-based materials limited the rising of the devices efficiency.MgZnO appears to be an ideal material for the application of solar-blind photodetectors because it possesses unique figures of merit,such as availability of lattice-matched single-crystal substrates,tunable band-gap(3.3 to 7.8 eV),relative low growth temperatures(100～750℃),nontoxic,and low defect density.Moreover,it also has a good potential application in deep UV region.In this paper,we obtained the pure cubic phase MgZnO alloy with 255 nm absorption edge by LP-MOCVD,and realized a solar-blind MgZnO photodetector.The peak responsivity of the detector locates at 250 nm,and cutoff wavelength at 273 nm.The MgZnO films were deposited on sapphire substrate by LP-MOCVD.We select bis(η5-cyclopentadienyl) magnesium(Mg(C5H5)2) as Mg source,dimethylzinc as Zn source and high purity oxygen as Osource.The growth temperature was fixed at 450℃,the pressure in growth chamber is at 20 kPa.The growth time lasts for 1.5 hour,then the films were taken out from the growth chamber.Energy-dispersive X-ray spectrum(EDX) measurement showed that the composition of the films is Mg0.52Zn0.48O.Secondly,the interdigital Au electrodes were fabricated on 50 nm Au layer by conventional UV photolithography and wet etching.The interdigital fingers are 500 μm in length,5 μm in width,and the spacing between the fingers is 2 μm.The XRD patterns of MgZnO thin films show only one sharp and strong diffraction peak at 36.62°,which is assigned as cubic(111) orientation.The HMFM of the diffraction peak is only 0.16°,which shows the high quality of the thin film.The diffraction peak indicates that the sample has a metastable cubic phase without phase separation.The absorption spectrum shows that the band gap of the Mg0.52Zn0.48Ois at 4.86 eV(255 nm),which has step in the phase region reported in literature(4.0～5.0 eV).As well known,the low growth temperature is beneficial to the cubic MgZnO film with large Mg composition,due to that the metastable state is more easily formed at low growth temperature.The responsivity of the detector exhibits the peak energy at 250 nm and cutoff wavelength at 273 nm,which satisfies for the wavelength-need of the missile flume detection in response wavelength region.关键词：MgZnO alloy thin film;solar-blind photodetector;MOCVD123|91|1更新时间：2020-08-12
- 摘要：In this study,on the base of literatures and traditional method of chemical precipitation process,we optimized the conditions of the experimental and prepared the lanthanide complexes of Tb(Sal)3·3H2Onanocrystallines with different sizes by the ammonia gas,a series of different proportion ammonia(1:1～1:16) and different pH buffer solution.In order to compare,the complex Tb(Sal)3·2H2O were obtained by the traditional chemical precipitation method.Using the elemental analysis,infrared spectrum,TGA-DSC,TEM and SEM,we confirmed that the construction,thermal properties and size of Tb(Sal)3·3H2O nanocrystalline and Tb(Sal)3·2H2O complex.In addition,fluorescence excitation and emission spectrum,ultraviolet absorption spectrums and the energy transfer process between the organic ligand and center terbium ions were investigated.Our results indicated that the sizes of the nanocrystalline of Tb(Sal)3·3H2O particle were in the range from 50 to 250 nm,the size of Tb(Sal)3·3H2O nanocrystallines was minimal and well-proportioned by the ammonia gas proportion 1:16,these nanocrystallines also exhibited terbium ion characteristic luminescence,the luminescence intensity of Tb(Sal)3·3H2O nanocrystallines prepared with the proportion 1:16 ammonia is the strongest.However,the size of the complex Tb(Sal)3·2H2O were 0.3～0.7 μm.These results of terbium complex Tb(Sal)3·3H2O nanocrystallins can provide a basis for further expanding its application in luminescent materials and magnetic materials.关键词：rare earth complexes;nanocrystalline;luminescent property;Tb(Sal)3·3H2O87|61|0更新时间：2020-08-12
- 摘要：Yb3+ is a good active ion.It has the simplest level structure,consisting of only two multiplets 2F7/2 and 2F7/2,which results in several advantages,such as no excited state absorption,no more up-conversion,and low quantum defect able to reduce the thermal loading.In addition,the longer fluorescence lifetime(about 1 ms) is propitious to store energy and the broad emission band allows the generation of high power laser pulse.But Yb3+ can only operate in a quasi-three level scheme.The terminal state of laser emission is very close to ground state,which results in high thermal population of the laser terminal state and strong re-absorption at the emission wavelengths,and high laser pumping threshold.In order to limit thermal population of the terminal level,a relatively strong crystal field increasing the Stark-splitting of the Yb3+ ground manifold as large as possible is expected.In our experiment,we discover that Yb3+ has bigger stronger Stark-splitting in the crystalline field of LuScO3.We take ammonia as precipitator,Yb2O3,Sc2O3 and Lu2O3 as starting mate-rials to prepare Yb:LuScO3 precursor by co-precipitation method.We obtained Yb:LuScO3 nano-polycrystalline powders by sintering the precursor at 1500℃.X-ray powder diffraction indicated that the polycrystalline Yb:LuScO3 belongs to the cubic phase,space group Ia3.Its lattice parameter a is 1.0126 nm,calculated by the least square method,and its size is about 50 nm.When excited at 937 nm,the strongest emission peaks of Yb:LuScO3 are at 976 nm and 1037 nm,the weaker peak at 1085 nm.According to its emission and absorption spectra,the energy structure of Yb3+ is determined.The overall splitting value of 2F7/2 is 1029 cm-1,which is larger than 785 cm-1 of Yb:YAG.By comparison to emission spectrum with Yb:YAG,the emission peaks move to longer wavelength and the emission spectrum band is very wide,which advantages to decrease laser threshold and improves laser efficiency.In addition,the broader emission band of Yb:LuScO3 is propitious to ultra-short pulses output.关键词：LuScO3;co-precipitation method;luminescence;nano-polycrystalline powder100|58|0更新时间：2020-08-12
- 摘要：This discovery of the light emission of porous silicon(PS) has led to much excitement at the prospect of developing Si based optoelectronic devices.However,the Si-H species,which are the passivation of the freshly prepared PS,are unstable,therefore the peak wavelength and efficiency of the luminescence is extremely sensitive to the preparation conditions and subsequent treatment of the sample,which has disturbing consequences for the suitability of this material for device applications.The growth of a high quality oxide around the surface of the Si crystals has been suggested as an alternative method of the PS surface passivation.Some progresses such as anodic oxidation,rapid thermal oxidation(RTO),hot water treatment and so on have been reported for the preparation of oxidized PS.In general,oxidation has a detrimental effect on the photoluminescence(PL) efficiency.SC-1(NH3H2O/H2O2/H2O,1:1:5,V/V) and SC-2(HCl/H2O2/H2O,1:1:6) solutions are two stan-dard oxidant and clean reagent and have been utilized in the traditional silicon semiconductor industry for many decades.In this work,we exploited these two novel oxidant solutions to the preparation of oxidized PS.The characteristic of the oxidized PSprepared by oxidizing the freshly prepared PSin the solutions of SC-1 and SC-2 have been studied by comparing with those prepared by thermal oxidization and those oxidized by other oxidants,such as HNO3 and H2SO4.It has been shown that SC-1 is an efficient oxidant for the preparation of oxidized PS with an intense PLand a simple and stable surface composition.The oxidized PSprepared in SC-1 for 30 s and then in SC-2 for 4 min has a more stable PLthan that from the sample oxidized in only SC-2.It means a stable surface composition is very important for the stable PL.关键词：porous silicon;photoluminescence;SC-1;chemical oxidation98|80|0更新时间：2020-08-12
- 摘要：Photonic crystals(PCs),also known as photonic band-gap materials,are artificial dielectric or metallic structures in which the refractive index modulation gives rise to stop bands for electromagnetic waves(EM) within a certain frequency range.The discovery of photonic crystals has opened up a promising tool to control the flow of light.A very interesting feature of light guided through photonic crystals is that the group velocity of the light may be reduced by orders of magnitude.There are several devices taking advantage of this property both in PC waveguides and in extended photonic crystal lattices.The excellent optical properties of PCs come from their special band structures.The band structures can be associated with the type of lattice that photonic crystals take on.Up to the present,many works have been devoted to study the properties of PCs which have hexagon,square and honeycomb lattices.The two dimensional Suzuki-phase lattice is the novel one,which firstly was brought forward in the context of sound propagation by sonic crystals and afterward its equivalent was introduced for photonic crystals.In this paper a complete research of the photonic band structure for Suzuki-phase lattice is presented,including the periodic array of air holes in a dielectric background and the periodic array of dielectric rods in air.With the help of plane wave expansion method,the impacts of scatter element radius and refractive index was investigated.The results demonstrate that the band-gaps are mostly for TM mode in the periodic array of air holes in a dielectric background,but the TEmode in the perio-dic array of dielectric rods in air.The complete band-gap presents itself in all type photonic crystals only when refractive index of the medium is larger enough.When refractive index is smaller,the complete band-gap doesn't emerge.For the periodic array of air holes in a dielectric background,the results demonstrate that in some rang of air hole radius the fifth and sixth bands are separated from each other distinctly.The dispersive curves for fifth band along Г-X1 direction and sixth band along X1-M direction are very flat,implying group velocity equal to zero.The modal field profiles were also calculated.From these results,we can find the fifth and sixth bands are mini-bands created by the coupling of defect modes.This phenomenon,which can be used for slow light engineering in photonic crystals,has not been found in the periodic array of dielectric rods in air and other lattices.关键词：Suzuki phase;photonic band gap;plane wave expansion method;defect mode116|82|0更新时间：2020-08-12
- 摘要：The emission of fluorescence in the high-energy pulsed fiber laser will reduce pump efficiency when high energy pump power is injected into doped fiber.The emission mechanism of the fluorescence in high energy pulsed fiber laser was analyzed based on the level model of Er3+ doped fiber(EDF).To explore fluorescence characteristic and improve the pump efficiency of high-energy pulsed fiber laser,a novel stimulation model is developed by combining the rate equation of Er3+ doped fiber laser and nonlinear Schrdinger(NLS) equation.With the proposed mode and numerical method,we have made an investigation on the longitudinal propagation characteristics of pump light and fluorescence,and on the relationship among the fluorescence power,the pump efficiency and Er3+ doping concentration.The numerical results show us that the pump and fluorescence power would decrease exponentially along the longitudinal axis of Er3+ doped fiber and the fluorescence power decrease faster than that of the pump power.The fiber laser would emit less fluorescence when pumped by 980 nm laser than that pumped by 1480 nm laser.The results also show that when the pump power is certain,the power of fluorescence emitting in the EDFwould increase as the doped density does,and the pump efficiency would decrease as the doped density increase.When the attenuation coefficient is certain,the fluorescence power would attenuate faster when the gain coefficient increases.Comparing with the previous work,we found that the results given by the proposed model are in good agreement with experimental results in the references.Therefore,in order to effectively depress the fluorescence and improve the pump efficiency,pump laser with the center wavelength of 980nm is suggested to be chosen,and the doped density should be decreased as much as possible when the gain is certain,or the gain should be increased as much as possible when the doped density is certain.114|88|0更新时间：2020-08-12
- 摘要：A modified phase demodulation method for measuring nanosecond fluorescence lifetime is introduced in this paper.The method is based on phase modulation technique and Fourier analysis of both the excitation and the emission waveforms.Excitation light is modulated by an arbitrary periodic wave.Emission of the sample follows the excitation light,is also modulated and with a delay because of the fluorescence lifetime.In the modified method,the first harmonics of the Fourier series are figured out from the excitation and the emission waveforms.The lifetime can be obtained by the relationship same as in the ordinary phase modulation method from the phase difference between the first harmonics.A test system,composed of an oscilloscope,a spectroscope and an excitation light source,was designed and developed.An LED light source modulated by a crystal oscillator is built at an acceptable cost for the system.The emission and excitation are detected by a spectroscope,converted to electrical signal by a photomultiplier tube,digitalized by a digital oscilloscope,and then transmitted to a computer.Fluorescence lifetime is then obtained by Fourier analysis of the emission and excitation waveforms.The relationship between the optimized modulation frequency and the range of the measured lifetimes is discussed.The lifetime of cresyl violet ethanol solution(0.0033 mol/L) measured with this method is(4.03±0.87) ns which is comparable with that by a commercial equipment.关键词：fluorescence lifetime;phase-demodulation measurement;Fourier series;LED121|130|0更新时间：2020-08-12
- 摘要：GaAs microtips array are fabricated by selective liquid phase epitaxy(LPE).Scanning electron microscopy(SEM) images show that the microtip is pyramid-like with the angle of the opposite sides about 71°.The height of the GaAs microtip is depended on the size of the growth window.In the experiment,the growth window of 60 μm×60 μm results in the microtip height of 42 μm.Furthermore,the field emission property of the tips array is also investigated.Aturn-on field of 5.1 V/μm and a good current stability are obtained.The field emission current increases from 6 μA to 74 μA when the electric field changes from 8.0 V/μm to 11.9 V/μm.The current fluctuation is found not to exceed 3% over a period of 3 hours.Furthermore,the non-linear field emission F-N curve of GaAs microtips array is also studied.The influence of the surface states of electrons and the field penetration are considered to be the reason for the non-linear field emission F-N curve.This achievement reported here represents a significant step towards the application of GaAs microtips array as a field emission material.关键词：microtip array;field emission;GaAs;liquid phase epitaxy103|77|0更新时间：2020-08-12
- 摘要：The a-Si/SiNx superlattice was prepared by RFmagnetron reaction sputtering technique and thermal annealing,which made Si nanocrystals appear in the a-Si films.In the experiment,the sample was inserted as saturable absorber into the resonator of Nd:YAG laser.The passive Q-switched operation of 1064 nm laser was achieved when cavity-length was short,and a single pulse waveform of 23 ns-wide was measured.In addition,a single pulse train with average pulse duration of 35 ps was obtained when the cavity-length was set to 124 cm.With the experiment phenomenon and the structure of film,the dynamics of the pulses formation is described;it was mainly ascribed to two-photon saturable absorption and fast relaxation processes of carriers excited in the nano-silicon with quantized states and interface states.The Q-switched output performance in different operating conditions was investigated by the way.关键词：laser techniques;nc-Si/SiNx superlattice thin film;Q-switched;mode-locked;RF magnetron reaction sputtering101|72|2更新时间：2020-08-12
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