最新刊期
卷 29 ， 期 4 ， 2008
- 摘要：After a boyhood spentin a number of countries,Bill Yen enrolled as an undergraduate student at theUniversity of Redlands,a private liberal arts andsciences university located in southern California.He spent the years 1952~1956 there,graduatingwith the BS degree in Physics.97|64|1更新时间：2020-08-12
- 摘要：This note is a brief,informal account of Bill Yen's pioneering investigations of optical dephasing in inorganic glasses.The work,carried out at the University of Wisconsin by Bill,together with his graduate students,post-docs and colleagues,had great impact on the field and led directly to our current understanding of the various mechanisms for dephasing and how they are reflected in the temperature dependence of the homogeneous linewidth.102|67|0更新时间：2020-08-12
- 摘要：The first decade at the University of Georgia(UGA)was an active and exciting time for Bill Yen,his students,post-docs and collaborators.In this paper,I highlight several papers that I hope capture this activity and provide a glimpse into this creative and productive period.97|87|0更新时间：2020-08-12
- 摘要：William(familiarly known as Bill by all his colleagues)Yen's life-long scientific interest in the magnetic properties of rutile structured antiferromagnetic materials(AFMs)began with his involvement in the discovery in 1965 of the magnon sidebands of MnF2 in optical absorption[1].A basic outline of this discovery is given elsewhere in this special issue of the Chinese Journal of Luminescence[2].A narrative discussion of events leading to this discovery appears in a contribution written by Bill and Robert White for a special edition of Low Temperature Physics on Antiferromagnetism[3].A quote from that remembrance highlights a quality that remained with Bill throughout his career:"The identification of these sidebands by a pair of young students and two post-docs illustrates how serendipity,a touch of good luck and reckless youthful enthusiasm often plays a role in scientific discovery".Bill's forever youthful enthusiasm coupled with creative insights into current research questions led to numerous pioneering discoveries throughout his career.This paper reviews Bill's contributions to developing techniques to exploit dichroism to study the magnetic properties of AFMs.Bill's publications in this area span more than 30 years,from 1971 to 2004.93|137|0更新时间：2020-08-12
- 摘要：A wide range of luminescent materials havebeen studied by optical spectroscopy techniques.Prof.William M.Yen has made tremendous contri-bution to this research area.One of his interests inthe recent years was in delocalization processes thatstrongly affect the luminescence efficiency[1].93|46|0更新时间：2020-08-12
- 摘要：LaF3 is an ideal low-phonon host for rare earthions due to its ability to form extensive solid solu-tions with all the RE ions.In 1964,professor Yen published his first paper on the Physical Review titled"Phonon-induced relaxation in excited opticalstates of trivalent praseodymium in LaF3"[1],whichwas Prof.Yen s very first work in the field of solidstate optical spectrosc troscopy and is widely cited.93|50|0更新时间：2020-08-12
- 摘要：In this paper,discrete Yb3+-Tm3+ co-doped LaF3 nanoparticles with controlled chemical composition and size distribution were readily synthesized using reverse micelles with microemulsions as confined reaction media.The morphology of the final product was characterized by the FESEM and HRTEM images.When the solid sample disperses in the ethanol without ultrasonic treatment,it is maize cob-like aggregator.The average diameter and length of the maize cob are about 110 and 575 nm,respectively.We suggested that the nanoparticles assemble into well-defined superstructures arising from the solvent evaporation,molecular cross-linking or interaction from surfactant molecules attached to specific nanoparticles crystal faces.After ultrasonic treatment for 30 min,the maize cob-like aggregator turns into a lot of nanoparticles owing to ultrasonic breach above a series of factors.The HRTEM image taken from individual nanoparticles indicates the crystalline nature,and the interplanar spacing of ～0.366 nm corresponding to the planes of pure hexagonal phase LaF3.The TEM image of the samples annealed at 300℃ for 30 minutes displays the average diameter of NCs increased to about 35 nm and is in good agreement with XRD result.In addition,the NCs exhibit nearly monodisperse property,which is in favor of optimizing luminescence of the sample.The nanoparticles present a bright blue upconversion luminescence under the 978 nm excitation from a laser diode,which provides a promising upconversion phosphor for optoelectronic or biological applications.关键词：nanoparticles;morphology;luminescence;upconversion108|295|0更新时间：2020-08-12
- 摘要：Sr3SiO5:Eu2+ and Sr3SiO5:Eu2+,Dy3+ phosphors have been synthesized through the solid-state reaction technique.We observed long lasting yellow phosphorescence in Sr3SiO5:Eu2+ and Sr3SiO5:Eu2+,Dy3+ phosphors,originating from 4f65d-4f7 transition of Eu2+,after UV exposure.The phosphorescence in Sr3SiO5:Eu2+ can be observed by naked eyes for more than 4 hours after the termination of excitation light.The decay patterns of phosphorescence and thermoluminescence curves demonstrate that introduction of Dy3+ into Sr3SiO5:Eu2+ can generate lots of shallow traps and deep traps.The generated deep traps prolong the phosphorescence up to 6 hours after UV irradiation.The depths of traps are obtained by fitting the thermoluminescence experimental data to the general order kinetics formula.关键词：phosphor;phosphorescence;the rmoluminescence103|44|4更新时间：2020-08-12
- 摘要：The trapping electrons have been used to explore the luminous property of the photoelectric materials.The self-trapping of an electron in a deformable lattice has been maintained interests of many scientists in the past decades.For weak electron-phonon(e-p)coupling,one expects that the electron behaves as a quasi-free particle("free polaron")and should be de-localized over all sites,whereas for very strong coupling it is conceivable that the electron is self-trapped by phonons.Various calculations for the ground-state energies of the polarons as functions of the e-p coupling strength have led to a transition from the quasi-free state to the self-trapped state.This transition phenomenon was also called "phase transition",though it is not a real phase transition in the general sense.An electron interacts with the acoustic and optical modes of the lattice vibration in a polar crystal.However,the abrupt change of the polaron state from the quasi-free state to the self-trapping state is usually caused by the short-range acoustic interaction,i.e.the electron-longitudinal-acoustic-phonon(e-LA-p)coupling,but not by the long range longitudinal-optical(LO)-phonon interaction.It has been indicated that the acoustic polarons in three-dimensional(3D)bulk materials are difficult to be trapped in most semiconductors and Ⅲ-Ⅴ compounds,even in alkali halides.Otherwise,the e-p coupling effects would be substantially enhanced in confined structures,such as two-dimensional(2D)and one-dimensional(1D)systems,so that the self-trapping transition may be easier to be realized.Farias et al pointed out that the critical e-LA-p coupling constant of the self-trapping transition of acoustic polarons in 2D systems is a certain value and independent of the cutoff wave vector.This conclusion is doubtful in Physics.The ground state energy and effective mass of the acoustic polaron in 2D systems are calculated by using the Huybrechts-like approach in two-step according to the weak and strong e-p coupling ranges.The self-trapping of the 2D acoustic polaron is discussed.The new self-trapping transition point is determined by the intersection point of the lines of ground state energies in weak and strong coupling ranges.It is found that the critical coupling constant of the self-trapping transition of the 2D acoustic polaron shifts toward the weaker e-p coupling with the increasing cutoff wave vector.The characters of the self-trapping of the 2D acoustic polron are qualitative consistent with the previous works of surface polaron and 3D acoustic polaron.There are both the quantitative and the qualitative differences in the critical coupling constants of the self-trapping of the 2D acoustic polarons obtained in this paper and the results given by Farias et al.Our results are more intelligible than that given by Farias et al in sense of the physics.关键词：acoustic polaron;ground state energy;effective mass;self-trapping116|88|0更新时间：2020-08-12
- 摘要：The study on organic electroluminescence devices(OELDs)have become one of the fascinating fields recently.Compared with inorganic electroluminescence devices,OELDs possess excellent features such as high efficiency,high brightness,rich color,wide visual view,low energy consumption,fast response,low cost,low-voltage dri-ving matching integrate circuit,large-area full-color display,excellent mechanical properties and so on.As the foundation of OLEDs,organic electroluminescent(OEL)materials are one of the key factors influencing the device performance.Therefore,organic electroluminescent(OEL)materials are also one of chemists' hot subjects in this field.In this promising field,many chemists are devoting themselves to investigating the synthesis techniques and photophysical behaviors of new and excellent electroluminescent materials.At present,OELDs have made great progress and developed for practicality and commodity,but their properties still be in the need of improvement in brightness,efficiency,lifetime,etc.The fluorene derivatives containing imino groups,N-(2,7-dibromo-9-fluorenylidene)aniline(NBFA),4-methyl-N-(2,7-dibromo-9-fluorenylidene)aniline(MNBFA)and 4chloro-N-(2,7-dibromo-9-fluorenylidene)aniline(CNBFA)as novel organic electroluminescent compounds were synthesized by the reaction of 2,7-dibromofluorenone and corresponding aniline derivatives.The structures of the compounds were characterized by 1H NMR,IR and MS.The photophysical processes of the compounds were carefully investigated by UV-Vis absorption and fluorescence emission spectra.The results show that the emission spectra exhibited obvious solvent effects and functional group effects.The emitting intensities were quenched by diphenylketone(DPKT),a quencher of electron acceptor,and gradually decreased with the increase of quencher.The quenching effect followed the Stern-Volmer equation well.The imino derivatives(NBFA,CNBFA,MNBFA)of 2,7-dibromofluorenone display not only a potential candidate as materials for organic electroluminescent devices,but also an intermediate for luminescent materials.关键词：imino;2;7-dibromofluorenone;aniline derivatives;fluorescence102|155|0更新时间：2020-08-12
- 摘要：A simple method for approximately accounting the lowest unoccupied molecular orbital(LUMO)level of RE-complexes from their exciplex emissions with low ionization potential hole transfer material,4,4',4"-tris[3-methyl-pheny(phenyl)amino]triphenylamine(m-MTDATA)was investigated.The EL emission peaks located at 590,607,and 656 nm,and the LUMO levels of the RE-complexes approximately were calculated to be about 3.0,3.06 and 3.21 eV for the Lu-,Gd-and Sc-complexes,respectively.关键词：exciplex;RE-complex;LUMO level100|239|0更新时间：2020-08-12
- 摘要：The motivation for developing silicon-based light emitters is the requirement of tiny light sources in the visible regions,which can be directly integrated into silicon chips for the analysis of different biological substances,for silicon optical couplers,and high-resolution low-cost micro displays.It is believed that the development of integrate circuit will open a door for the continuous increasing of silicon-based light emitters predicted by Moore's law.Many efforts,such as bulk silicon,Si nanocrystals,and rare earth(RE)coupled Si nanocrystals have been extensively studied.Weighing the studies mentioned above,rare RE-doped silicon light emitter,which has intense light emission even at room temperature,is a better candidate.In this report,the photoluminescence of Tb implanted SiNx films grown by plasma-enhanced chemical vapor deposition(PECVD)was investigated.And the effects of surface plasmon on the photoluminescence emission decay time of Tb3+ doped SiNx films with different sized of Ag islands films were investigated.The photoluminescence(PL)and time resolved photoluminescence(TRPL)at room temperature show that the PL of SiNx:Tb3+ film has the highest intensity at 547 nm with corresponding emission decay time 708 ms.After sputtering silver films,the TRPL of Tb3+ ions shows the decrease of the emission decay time.An increase of emission decay time was observed due to the increased size of Ag islands after rapid thermal processing(RTP).We find good agreement between our experimental results and those predicted by a classical theory,which assumes the emitter to be a damped oscillating electric dipole.Therefore,it allows one to be confident that the silver islands do altered the emission decay time which correspondingly improve the internal quantum efficiency of the SiNx:Tb3+.关键词：PL;emission decay time;Tb;surface plasmon104|67|1更新时间：2020-08-12
- 摘要：Eu2+-doped CaSi2O2N2(Ca1-xEuxSi2O2N2)has been prepared by solid-state reaction method,and the optical properties of the alkaline-earth silicon-oxynitride phosphor have been investigated.Eu2+-doped CaSi2O2N2 displayed a single broad emission band peaking at 556~568 nm depending on the europium concentration.The emission bands in the spectra of Eu2+-doped CaSi2O2N2 were assigned to the allowed transition of Eu2+ from the lowest crystal field component of 4f65d to 4f7 ground-state level.It has been demonstrated that the Eu2+-doped CaSi2O2N2 phosphor absorbs strongly the UV-blue part of the electromagnetic spectrum which makes this material attractive as the conversion phosphor for white light-emitting diodes(LEDs)applications.We have also shown that the optical properties depend greatly on the Eu2+ concentration.A systema-tic red shift of the emission band is observed as the Eu2+ concentration increases.The results indicate the photoluminescence properties can be tailored by controlling the Eu2+ concentration.Moreover,for all samples,starting at low Eu2+ concentration,the emission intensity rises to a maximum at a Eu2+ concentration of x=0.06 and falls again when the Eu2+ concentration continues to increase.This decrease in emission intensity beyond a critical concentration can be explained by concentration quenching,which is mainly caused by the energy transfer between Eu2+ ions.关键词：oxynitrides;luminescence;white-light LED112|65|3更新时间：2020-08-12
- 摘要：High-power diode lasers based on GaAs semiconductor bars meanwhile are well established as reliable and highly efficient laser sources.Continuous improvement of the semiconductor material itself as well as mounting and cooling techniques during the last years have led to increased output power and high lifetimes.In many cases high power diode lasers are on the way to replace flashtubes for solid state laser pumping.By realizing arrangements of many high-power diode laser elements,e.g.diode laser stacks,the overall output power can be increased further up to the kW range.In this power level,we can have many important applications,such as surgery,welding of polymers,soldering,coatings and surface treatment of metals.But there are some applications,which require much higher power and brightness,e.g.hardening,key hole welding,cutting and metal welding.In addition,high power diode lasers in the military also have important applications.So all developed countries have attached great importance to high-power diode laser system and its applications.Germany is developing initiative "BRIOLAS"(brilliant diode lasers)program,the German Federal Ministry of Education and Research (BMBF) is supporting the BRIOLAS-initiative with about 30 M.The United States have launched "SHEDS"(High Efficiency Diode Sources)from 2005.Now Germany laserline corporation have products,that direct diode laser system have largest output power of 10000 W,and fiber coupled diode laser system have largest output power of 8 000 W into the 1.5 mm diameter of the fiber.We know that under certain circumstances the light,which is emitted from the diode laser bar is linearly polarized,and the polarization degree can be 95%~98%.So polarization coupling technology makes two laser beam of perpendicular polarization direction reciprocally together,that is another effective way to improve the power and the brightness of diode lasers.After fast axis collimating,the polarization direction of one laser stack is rotated 90°through a half-wave plate,thus,the polarization directions of two laser stack are vertical reciprocally.The beams of two lasers are incident to polarization filter;one transmits through it,and the other is bent on it.Finally two beams combine to one.In this paper,it mainly introduces the principle of polarization coupling,technique route,experiment result and analysis.The polarization coupling efficiency can achieve 90% for two LD stacks with seven bars whose emission wavelength is 808 nm.The efficiency of 67% can be achieved after focusing to the beam size of 4.5 mm×4.5 mm.关键词：808nm;high power diode laser;polarization coupling;beam coupling113|118|1更新时间：2020-08-12
- 摘要：AlxGa1-xN material has a direct band gap between 3.42 eV and 6.2 eV at room temperature,the corresponding cut-off wavelength flexible from 365 nm to 200 nm.It also covers the spectrum obtained with conventional gas and solid-state ultraviolet(UV)lasers,therefore it is necessary for UV photo-detector and deep-ultraviolet light emitting diodes(deep UV-LED).For the fabrication of these devices,thick AlxGa1-xN layer with high Al composition and high crystalline quality are essential.A major obstacle concerning the growth of such AlxGa1-xN layer is the large mismatches in the lattice constants and thermal expansion coefficients between the AlxGa1-xN and the commonly used substrate of sapphire.Crack start to be generated because of tensile strain at a thickness of less than 100 nm for Al0.25Ga0.75N once it directly grown on GaN/Sapphire.The production of crack-free thick AlxGa1-xN ternary layer with high Al composition has also been a challenging issue.It has been reported that low temperature AlN(LT-AlN)IL,or high temperature AlN(HT-AlN)IL,or AlN/AlxGa1-xN SLs IL is introduced to improve the quality of AlxGa1-xN layer.Introduction of GaN/AlxGa1-xN superlattices(SLs)interlayer(IL)is an effective technique for releasing stress in AlxGa1-xN and decreasing TDs density in AlxGa1-xN epitaxial film.The influence of GaN/AlxGa1-xN superlattice (SLs) interlayer (IL) on the strain and threading dislocations(TDs)density of AlxGa1-xN epitaxial film grown on GaN/sapphire were investigated.Probing of phonon frequency by Raman scattering is one of the most convenient methods for charactering residual stress.The strain in AlGaN epitaxial film is obtained via Raman spectroscopy.Edge TDs density and screw TDs density of AlxGa1-xN film are obtained by X-Ray Diffraction(XRD).As thickness of superlattices period increase(well and barrier have the same thickness),both the edge TDs and the screw TDs density of AlxGa1-xN film decrease,and minimum tensile strain of AlxGa1-xN film is obtained for the sample with ten periods 5 nm/5 nm GaN/Al0.3Ga0.7N SLs IL.When the well thickness of GaN/Al0.3Ga0.7N superlattices is keeped and the barrier thickness of superlattices is increased to 8 nm,namely using ten periods 5 nm/8 nm GaN/Al0.3Ga0.7N SLs IL,compressive strain in AlxGa1-xN epitaxial film is achieved.Minimum TDs density of AlxGa1-xN film is obtained for the sample with ten periods 8nm/8nm GaN/Al0.3Ga0.7N SLs IL.The TDs density indicates that SLs IL can not only restrain edge TDs but also restrain screw TDs partly.Transmission electron microscopy(TEM)measurement demonstrates that the SLs IL can bend or end the TDs or make TDs incorporate,which can lead to TDs density reduction in AlxGa1-xN epitaxial film.And the inclination of edge TDs induced by relaxation strain in AlxGa1-xN film was observed,which resulted in a compressive strain relaxation of AlGaN layer.The strain relaxation of compressively strained AlxGa1-xN by inclined threading dislocation is calculated using TEM results.Above all,the AlxGa1-xN epitaxial film with compressive strain and low TDs density is obtained by the technique of GaN/AlxGa1-xN SLs IL.It is a foundation for the growth of AlxGa1-xN epitaxial film with high crystalline quality and high Al composition.关键词：AlxGa1-xN;superlattices(SLs);strain;threading dislocations(TDs)density106|60|2更新时间：2020-08-12
- 摘要：Combining phosphor with LED chip has become the most common method to realize white light output for white LED.Thermal conduction and phosphor coating are two key factors that influence on the quality of products.The spatial distributions of color temperature and chromaticity are the crucial parameters of power white LED used in lighting.The range of color temperature deviation within single white LED which can be distinguished by human eyes is from 50 K to 100 K.The uniformity of color temperature of white LED devices still cannot achieve the optimized standard,because the color temperature deviation of single product can even attain 800 K.This can be attributed on the nonuniformity of phosphor coating on the LED chip.Therefore,the uniformity of light output is of great importance as white LEDs found their way in the lighting application.The conventional dispensing method(or dipping method)for phosphor coating,which is much popular currently used in the LEDs industry,was introduced in this paper.Further,some modification had been made in the structure configuration of the phosphor layer to improve the uniformity of light output of white LEDs based on the dispensing process.Nine-point scheme had been adopted to measure the spatial distribution of brightness and chromaticity of light output of different LEDs samples with different process parameters.Although these modification has improved the uniformity of chromaticity of white light spot in a certain extent,as a whole the uniformity of white light output of devices made by employing conventional dispensing method of phosphor coating is still not good,and deviations of spatial coordinates of white light spots are larger than those of 0.01 that human eyes can distinguish.This can be ascribed to the cumber shape of phosphor coating.Since the process of phosphor coating is operated by handwork,the thickness of phosphor layer is not uniform which causes a big influence to the performance of products.In addition,the consistency of products of same batch is not good,and deviation of color temperature and chromaticity among different products is large.It can be explained that the process of phosphor dispensing cannot be well controlled among different products.All of these indicate that the conventional phosphor coating method-dispensing has lots of defects.To eliminate and overcome these defects,a novel phosphor coating method termed conformal coating,which can largely improves the uniformity of phosphor layer,should be emphasized.关键词：white LEDs;uniformity of light spot;spatial distribution of chromaticity108|105|5更新时间：2020-08-12
- 摘要：The performance of optically pumped semiconductor vertical external-cavity surface emitting laser(OPS-VECSEL)is influenced by many parameters,so the theoretical analysis and simulation are very important.We constructed a 980 nm optically pumped semiconductor vertical external-cavity surface emitting laser(OPS-VECSEL)with active region of In0.159Ga0.841As/GaAs0.94P0.06 system pumped by 808 nm laser diode module.Employing the PICS3D software,the characteristic parameters of OPS-VECSEL were calculated.The performances of device especially the threshold and the optical-optical conversion efficiency were influenced by the chip radius,the number of quantum well and the reflectivity of external-cavity mirror.Calculation and analysis show that the chip radius affect optical-optical conversion efficiency.The output power and optical-optical conversion efficiency are influenced by the number of quantum wells and the reflectivity of external-cavity mirror.Thus we should design and grow the laser structure according to the need.关键词：semiconductor lasers;vertical external-cavity surface emitting laser;optically pumped;quantum well;theoretical simulation119|109|3更新时间：2020-08-12
- 摘要：A series of MgxZn1-xO(0≤x≤0.3)thin films were successfully fabricated by sol-gel method.The structural and optical properties were studied using XRD and photoluminescence spectrum.The results indicate that the MgxZn1-xO thin films have hexagonal wurtzite single phase structure and a preferred orientation with the c axis perpendicular to the substrate.It was observed that there is an critical annealing temperature(700℃)of the MgxZn1-xO(0.1≤x≤0.3)thin films preheating at 350℃,when annealing below this temperature,the intensity of(002)XRD peak increased,and the PL spectra of MgxZn1-xO(0.1≤x≤0.3)thin films show both UV emission and green emission;when annealing above this temperature,the intensity of(002)peak decreased while(100)and(101)peak appeared,and the PL spectra of MgxZn1-xO(0.1≤x≤0.3)thin films show only UV emission.The impurity concentration also affect the emission,when annealing below 700℃,the PL spectra of pure ZnO thin films show only UV emission,while the PL spectra of the MgxZn1-xO(0.1≤x≤0.3)thin films show both UV emission and green emission.关键词：MgxZn1-xO films;sol-gel method;XRD;photoluminescence96|61|0更新时间：2020-08-12
- 摘要：With the advance in the nanofabrication technology,there has been a great deal of interest in the investigating of quasi-zero-dimensional electronic systems(quantum dots).Since its newly opto-electric and electron transport characteristics,it is becoming a heat field in the study of quantum fanctional device.Many investigators studied the properties of the polaron in a quantum dots in many aspects by a variety of theoretical and experimental methods.Recently,the properties of strong and weak-coupling of the polaron in an asymme-tric quantum dot have been studied using the linear-combinating operator method by the present authors.However,using improved linear combination operator method,the properties of the polaron in an asymmetric quantum dot has not been investigated so far.In this paper,the properties of the vibrational frequency and the interaction energy of weak-coupling polaron in an asymmetric quantum dot were studied by using a improved linear combination operator and unitary transformation method.The relations of the vibrational frequency and the interaction energy of the weak coupling polaron in an asymmetric quantum dot with the transverse and the longitudinal effective confinement length of the quantum dot and the electron-phonon coupling strength are derived.If the units have been chosen in the usual polaron units(2m=h=ωLO=1),we perform a numerical calculation.The results show that the vibrational frequency and the interaction energy of the weak coupling polaron in an asymmetric quantum dot will increase strongly with decreasing the transverse and longitudinal effective confinement length of quantum dot.Those attributed to interesting quantum size effects also appear.The interaction energy of weak coupling polaron in an asymmetric quantum dot will decrease with increacing the electron-phonon coupling strength.关键词：asymmetric quantum dot;polaron;improved linear combination operator;interaction energy103|80|0更新时间：2020-08-12
- 摘要：Recently the development of emissive materials for organic light-emitting diodes(OLEDs)in the NIR region is becoming a major research subject since such materials can provide a new type of NIR light-emitting device applicable to future optical communication and information processing.However,most of materials for use in NIR OLEDs were organic complexes with trivalent rare earth ions such as Er3+,Nd3+,Tm3+ and Yb3+.However,since the f-f transition is,in principle,a parity-forbidden process,there is a substantial problem as regards the EL quantum efficiency.In this paper an organic material containing no rare earth ions:tetra-(2-isopropyl-5-methylphenoxylphthalocyaninato)titanium(Ⅳ)oxide was prepared and characterized by 1H NMR,MS,elemental analysis,UV-vis absorption spectra,NIR PL spectra and cyclic voltammetry.The OLEDs based on this TiOPc was prepared by spin-coating and thermal evaporation.The structure of device is(ITO/PVK:TiOPc/BCP/LiF/Al).From 1H NMR,MS,elemental analysis we could found the excellent purity of this TiOPc.Cyclic voltammetry give us HOMO and LOMO level as-5.26,-3.69 eV,respectively.The NIR PL spectra show there is a broad band peaked at 1080 nm.The electroluminescent(EL)devices with the TiOPc complex as the emitting layer were fabricated and they exhibit EL emission peaked at 1050 nm.In the TiOPc-doped devices the optimum concentration was 30%(mass fraction),whit the intensity of NIR EL extremely high.This work is an original work of OLEDs in NIR region,so the efficiency and life should be improve in the future.关键词：TiOPc;near-infrared;OLEDs99|88|0更新时间：2020-08-12
- 摘要：The steady-static and transient luminescence in porphyrin side chain polymer P[(por)A-S] doped in PMMA were studied by using transient and steady-state fluorescence spectroscopic technique.The results show that with the decrease of the interchain distance of P[(por)A-S],the interactions of the porphyrins enhance which increase the nonradiating transition.As a result,the luminescence efficiency and the lifetime are inversely proportional to the interchain distance of P[(por)A-S].We also discuss the origin of the luminescence of P [(por)A-S] doped in PMMA.关键词：porphyrin side-chain polymer;luminescence;interchain molecular interaction128|69|1更新时间：2020-08-12
- 摘要：Self-Q switched fiber lasers utilizing the mechanism of stimulated Brillouin scattering(SBS)can increase the output power by several magnitudes and the scale of high output power makes them to be very attractive laser sources for applications in many technological areas,such as telecommunication,material proces-sing,laser surgical,range finding and remote sensing.In the presented work,the generation of pulse laser exploiting SBS phase conjugation in fiber was investigated theoretically and experimentally,and how the length of SBS medium affected the attribute of laser output was paid prior attention in our study.Numerical simulation was performed to study the waveform and the sequence of laser pulse.The waveform obtained by numerical computation was coincident with the curve described the relationship between reflectivity of SBS phase conjugation mirror and the time.The results show that changing Q value in resonant cavity by utilizing SBS phase conjugation is feasible.To investigate the attribute of laser output at different length of SBS medium,an all-fiber Er-doped Q-switched laser was designed,in which a 974 nm laser diode was used as pump source,Er-doped fiber(EDF)with length of 3 m was used as gain medium,a fiber Bragg grating(FBG)was used as fixed cavity mirror and standard single-mode fiber(SMF)G.652 with length of 2 m,1.5 m and 1 m were used as SBS pool individually.At the same time,an optical spectrum analyzer(ANDO6319),a digital oscilloscope with 5 Gs/s(Tektronix TDS3052)and a optical power meter(ANDO AQ2140)were used to monitor the optical spectrum,temporal pulse shape and average power simultaneously.The high-speed photodetector designed by ourselves broadened the pulse duration by 20 times so as to reduce the damage to the apparatus caused by the high peak power of the laser pulses.When the length of SMF was 1.5 m,a train of pulse laser was generated with pulse duration of 2.6 ns,pulse period of 58.23 ns,average output power of 7.35 mW at pump power of 45 mW.Decreasing the length of SMF to 1 m,remarkable pulse laser with dual-peaks was obtained and the pulse period of it was 26.47 ns.Increasing the length of SMF to 2 m,only irregular stochastic pulsations were seen.Experiment data indicate that the length of SBS medium is vital to the formation of phase conjugation mirror.If it is too long,pulse laser can't be generated for the lack of fixed conjugation relation between Stokes lines,on the contrary,dual-peaks laser pulses occur for the change of photon lifetime in orthogonal polarized modes.Once the laser pulses are generated,the characteristics of laser pulses are only correlated with the stochastic characteristics of SBS and the pulse form maintain changelessness as the increase of the pump power.By means of these obtained experimental results,we can select proper length of SBS medium to yield perfect output pulse shapes,which enable this kind of self Q-switched fiber lasers to be more practical.In addition,enhanced stabilization of the pulsation can be achieved by modulating the pump power to be in resonance with the repetition rate.关键词：laser technology;fiber laser;Q-switched fiber laser;stimulated Brillouin scattering;phase conjugation113|113|1更新时间：2020-08-12
- 摘要：In recent years,solar-blind photodetectors have attracted much attention due to their applications in missile plume sensors,flame detectors,chemical-biological agent sensors,and space-to-space communications.MgZnO appears to be an ideal material for the development of solar-blind photodetectors because it possess 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℃),and high radiation hardness.In this paper,we demonstrate a solar-blind MgZnO photodetector made from MgZnO films.The peak responsivity of the detector lies at 225 nm,and cutoff wavelength at 230 nm.Solar-blind photodetectors based on MgZnO thin films were fabricated through two steps:the preparation of Mg0.7Zn0.3O thin films and the interdigital Au-electrodes.The experimental procedure was as follows:Firstly,high-purity Mg0.5Zn0.5O ceramic disk was used as the target.The sputtering chamber was evacuated down to 3×10-4 Pa before introducing the sputtering gas.Ar and O2 gases were introduced into the sputtering chamber through two separate mass flow controllers with the rates of 60 and 20 sccm(standard cubic centimeter per minute),respectively.The working pressure in chamber was kept at 1 Pa,the substrate temperature at about 450℃,and the rf power at 100 W.The sputtering process lasted one hour,then the films were taken out of the growth chamber.Energy-dispersive X-ray spectrometer(EDX)measurement showed that the composition of the films is Mg0.7Zn0.3O.Secondly,the interdigital Au electrodes,which were defined on 50 nm Au layer by conventional UV photolithography and wet etching were coated onto the film surface.The interdi-gital fingers are 500 μm in length,5 μm in width,and the spacing between the fingers is 5 μm.The absorption spectrum of the MgZnO films shows strong absorption at 230 nm,and very weak absorption from 320 to 600 nm.Note that there is a tail in the range from 245 nm to 300 nm in the absorption spectrum,which may be attributed to the nonuniformly distribution of Mg composition or the phase separation.The photodetector shows a peak response at 225 nm with the cutoff wavelength at 230 nm,which is in accordance with the absorption spectrum.Until now,none report on the MgZnO photodetector prepared by RF magnetron sputtering with the peak spectral response short to 225 nm can be found to the best of our knowledge.We think that by optimizing the growth conditions and reducing the composition fluctuations and phase separation occurred in the films,photodetector with improved performance can be expected.关键词：MgZnO alloy thin film;solar-blind photodetector;radio frequency magnetron sputtering122|93|1更新时间：2020-08-12
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