最新刊期
卷 22 ， 期 4 ， 2001
- 摘要：Dependence of polarity of hexagonal GaN on that of GaAs(111) substrates was investigated.GaN grown by MOVPE and MOMBE with a high Ⅴ/Ⅲ ratio followed polarity of the GaAs substrate;a layer grown on the(111) A-Ga-surface showed Ga polarity and that on the(111) B-As-surface showed N polarity.However,GaN grown on GaAs(111) B surface showed Ga polarity when the layer was grown by HVPE,MOMBE with a low Ⅴ/Ⅲ ratio,or with an AIN intermediate layer.The reason is not made clear yet,but these results suggest that HVPE growth or an MN high temperature buffer layer gives a better quality GaN.关键词：GaN;polarity control;growth method;growth condition103|73|0更新时间：2020-08-11
- 摘要：As recently remarkable developments for MBE-grown GaN have been reported,a high growth rate of GaN by RF-MBE,and the high electron mobility values could be obtained.The polarity control and the threading dislocation reduction in GaN layers grown on sapphire sub-strates by RF-MBE are discussed in this paper.The polarity of GaN was controlled to N-polarity by growing GaN directly on sufficiently nitrided sapphires,and Ga-polar GaN was realized by uti-lizing the high-temperature-grown A1N nucleation layers.For both N-and Ga-polar GaN,the in-troducing high-temperature-grown AlN multiple intermediate layers is effective to suppress the threading dislocation propagation.The reduction of dislocation brought about the improved room temperature electron mobility,332cm2/V·s for Ga-polar GaN and 688cm2/V·s for N-polar GaN.关键词：GaN;RF-MBE growth;polarity control;threading dislocation92|205|1更新时间：2020-08-11
- 摘要：In the present work,the polarity-controlled growth of GaN on sapphire substrate by LP-MOVPE and RF-MBE is demonstrated.The mechanisms for polarity selection of GaN on sapphire substrate both in MOVPE and MBE growth are discussed based on the "two monolayers of Al" model,which also gives a reasonable explanation to the polarity reversion mechanism by AlN.Through the polarity-controlled growth,surface morphology and electrical property of GaN grown by RF-MBE is improved;a three-step growth method is developed for LP-MOVPE,so that high quality GaN films can be obtained in a more epitaxial way on sapphire substrate.关键词：growth of GaN;MOVPE;RF-MBE;polarity control115|105|0更新时间：2020-08-11
- 摘要：The optical bistability device,as a basic device for optical computer,its most attractive property will be the ultrahigh rate of opening and closing.The ultrahigh rate of opening can be realized by now.However,limited by the life of carriers in semiconductor,the ultrahigh rate of closing is difficult to realize.In this paper,a new type of(CdZnTe,ZnS)/ZnTe composite quantum wells structure was devised for im-proving the rate of closing in the optical bistability device.In this structure,the ZnS and ZnTe form Ⅱ-type superlattices structure,and the band gap of ZnS is wider than that of CdZnTe.Then,the introduction of ZnS well layer will have no effect on the nonlinear property of ZnTe/CdZnTe.The exciton in the CdZnTe well layer will cross through the ZnTe barrier layer into the ZnS well layer in a very short time.Then,the tunnelling can reduce the life of exciton and realize the high closing rate of the optical bistability device.Samples were fabricated by low-pressure metalorganic chemical vapor deposition(LP-MOCVD) on GaAs(100) substrates.Diethyl-telluride(DETe),dimethyl-cadmium(DMCd),dimethyl-zinc(DMZn) and sulfureted hydrogen(H2S) were used as precursors.The system pressure of chamber was kept at 4.0×104Pa and the temperature was at 420℃.Samples consisted of a ZnTe buffer layer,40 periods of composite quantum well structure(CdZnTe well layer-ZnTe barrier layer-ZnS well layer-ZnTe barrier layer) and a ZnTe capping layer.Different sample had different thickness of ZnTe barrier layer.Through studying PL spectra of the samples,the luminescence of cross exciton was obtained.The tunnelling of cross exciton was verified by analysing the PL intensity rate of carriers provider well and carriers receiver well.Furthermore,the multilevel Raman peak can also verify the existence of tunnelling during the process of lu minescence.Those conclusions indicated the validity of this composite quantum wells device for reducing the life of exciton in the CdZnTe well and provided the evidence in experiment for further research of ultrahigh rate optical switch device.关键词：composite quantum well;exciton tunnelling102|135|2更新时间：2020-08-11
- 摘要：Hydrogenated amorphous carbon films have many unique properties,they have attracted much attention because of their applications in many kinds of optoelectronic devices such as light emitting diodes and field emission devices.It was well known that the film structures and properties were varied in a wide range by changing many factors such as hydrogen content and treatment.In this paper,the influence of hydrogen dilution on the optical properties of a-C:H films was studied.The a-C:H films were prepared in a capacitance coupled plasma enhanced vapor chemical deposition system at 13.56MHz.The gas mixture of CH4 and H2 was used as source and the flow rate of the H2 was changed.The structures and optical properties were investigated by Fourier-transform infrared spectra,photoluminescence spectra and optical absorption spectra.It was concluded that hydrogen dilution can,to some extent,etch the weak bonds in films,decrease the size of sp2 clusters,and increase the sp3 C-Hn con-tent which results in the increase of the optical band gap of a-C:H films.The optical band gap increased from 2.57eV to 2.72eV with increasing hydrogen dilution ratio.Consequently,the PL peak energy has a blue shift from 2.5eV to 2.75eV under the excitation with 3.54eV light.The further increase of the hy-drogen dilution will induce the change of the bonding configurations in the carbon films,which results in the multiple PL bands in the luminescence spectra at room temperature.The a-C:H films include both sp3 C-C,C-H and sp2 carbon related clusters.The C=C bonds can exist in the form of olefinic chains,six-fold ring aromatic species et al.Under different hydrogen dilution conditions,the main C=C structure in the sp2 clusters was different,which induces the different structures and optical properties of a-C:H films.关键词：hydrogen dilution;amorphous carbon;photoluminescence112|101|0更新时间：2020-08-11
- 摘要：Enhanced 395nm ultraviolet photoluminescence(PL) has been obtained from the SiO2/Ge:SiO2/SiO2 sandwiched structure.As light source for optical data storage system,this structure will be very useful in optoelectronic integration.Simultaneously,infrared light emission peaked at 780nm was also observed in this novel structure.In this paper,we discussed the origin of the infrared PL in terms of infrared spec-troscopy(FT-IR) and FL excitation(PLE) spectra.The constancy of the 780nm PL band with annealing temperature does suggest that it can not arise from both the quantum confinement on Ge,Si nanocrystals and the oxygen deficient defects of Ge and Si,because PL from these radiative centers all have peak shifts to some extent.The experimental results from FT-IR strongly suggest that the Ge-O-Ge vibration intensity and the 780nm PL intensity have a similar behavior with annealing temperature.So it is reasonable to be-lieve that the infrared PL band is very related to Ge oxides.Further PLE examination results indicate that it has the similar excitation process to the 395nm ultraviolet PL which comes from TⅡ'(T)→S0 optical transitions in GeO color centers,which has been confirmed by many research groups.So we believe that the 780nm PL should also originate from GeO color centers.The schematic diagram of electronic states of GeO molecule is presented to describe the carriers' excitation and recombination process in this kind of centers.The TⅡ'→S0 optical transitions in GeO color center is responsible for the infrared PL.In GeO molecules,all radiative transitions are intramolecular.Thus the PL bands from the GeO color centers are hardly influ-enced by the SiO2 network.That is why 780nm infrared PL has no wavelength change with different annealing temperature.Our work paves the way for the sandwiched structure's device applications.关键词：photoluminescence;magnetron sputtering;infrared light emission;GeO color center98|45|1更新时间：2020-08-11
- 摘要：With the development of magneto-optical technology,the properties of the polaron in magnetic field have been of considerable interest.Larsen proposed a novel operator method to investigate the properties of 2D polarons.Peeters et al.discussed the properties of the magnetopolaron using the Feynmann path-integral approach.Wei and co-workers studied the induced potential and the self-energy of an interface magnetopolaron using the Green-function method.Huybrechts proposed a linear combination operator method,by which a strong coupling polaron was discussed.Later,many scholars studied the strong coupling polaron in many aspects by this method.The properties of the surface magnetopolaron have been discussed by the method of a linear combination operator and a perturbation by the present authors and co-werkers.In fact,the case of finite temperature is more significant.A lot of scholars studied the properties of the temperature of a polaron by a variety of different theoretical method.Saitok obtained that the effective mass of a polaron decreases with increasing temperature by means of the Feynmann path-integral approach.Many scholars got a alike conclusion also.This conclusion has been gained by the present authors and co-workers.However,Gu acquired an opposite result.Later,we studied the temperature dependence of the effective mass of the strong coupling magnetopolaron in polar crystals by means of the unitary transformation and an improved linear combination operator method again.The temperature characteristic of the effective mass was discussed in detail at different approximation calculation level.The result illustrated that the different approximation calculation level could provide two completely contrary conclusions on temperature depen-dence of the effective mass of the magnetopolaron.Using the different approximation calculation level,one can provide two complety contrary conclusions on temperature dependence of not only the effective mass of the magnetopolaron but also other of the mag-netopolaron.In this paper,the relationship between the mean number n of strong coupling magnetopolaron in polar crystal and magnetic field B and temperature T are studied by the method of the unitary transfor-mation and the linear combination operator.The magnetic field and temperature dependences of the mean number of the magnetopolaron are discussed in the different approximation calculation level.Numerical cal-culation for the RbCl crystal,as an example,are performed.The mean number of the magnetopolaron decreases with increasing temperature and increases with increasing magnetic field when the approximation calculation level is lower.The mean number of the magnetopolaron increases with increasing temperature and decreases with increasing magnetic field when the approximation calculation level is higher.关键词：approximation calculation level;strong coupling;mean number of the magnetopolaron;properties of temperature;properties of magnetic field92|109|0更新时间：2020-08-11
- 摘要：There have been a large number of documents and patents on organic/polymer electrolumi-nescence devices,in addition a good many organic and polymer materials have been successfully synthesized since the first report of high performance double-layer organic light-emitting device(OLED) by C.W.Tang in 1987,and much progress has been made in this field.Study on the dye-doped organic light-emitting diodes is very significant.And a useful technique for altering the color of OLEDs involves the doping of a small amount of a fluorescent dye into one of the organic layers of an OLED.But little study on the color-tunable organic electroluminescence by the voltage applied at a doping level is reported.In this work,dye(Rubrene) was doped into poly( n-vinylcarbazole)(PVK) at different weight ratios and the characters of photoluminescence and electroluminscence were studied.The device structure of ITO/PVK:Rubrene/Al was employed.The result shows that there are great difference between the photolumi-nescence and electroluminescence at a doping ratio of 2wt%.It is concluded that energy transfer in these dye-doped devices occurs by Forster energy transfer processes.And the trap effect of electrons of Rubrene on holes of PVK results in different combination probability of PVK exciton in photoluminescence and electroluminescence.The two cases result in the difference between the spectrum of photoluminescence and that of electroluminscence.At the same time,EL devices with Rubrene doped PVK as emission layer are color-tunable when the bias voltage was increased.It indicates that the energy transfer process from PVK to Rubrene is not complete.And the combination probability of PVK exciton which does not contribute to the emmision of Rubrene is increased when the bias voltage increases.关键词：organic electroluminescence;color-tunable by voltage modulation;energy transfer112|89|0更新时间：2020-08-11
- 摘要：An understanding of the surface and interface states of the organic material and the underlying anode material is meaningful for organic light-emitting devices(OLEDs).The tris-(8-hydroxyquinoline) aluminum(Alq3)/indium-tin oxide(ITO) samples were fabricated with traditional vacuum deposition.The surface and interface electronic chemical states of the Alq3 and the underlying ITO have been investigated by X-ray photoelectron spectroscopy(XPS).The analysis on XPS spectra of the surface of the Alq3/ITO structure shows that,in Alq3 molecule,the binding energy(Eb) of Al atoms is 70.7eV and 75.1eV,corresponding to Al(0) and Al(Ⅲ),respectively.The binding energy of C atoms is 285.8eV,286.3eV and 286.8eV,corresponding to C atoms of C-C groups,C-O and C-N bonds,respectively.The N1s main peak locates at 401.0eV,corresponding to N atoms of C-N=C bonds.O atoms mainly bond to H atoms,and the bonding energy is 532.8eV.The N and O atoms also interact with Al atoms through coordination bonds.In order to investigate the interface electronic states of the Alq3/ITO structure,the samples are sputtered by argon ions beam.The analysis on XPS spectra of the interface of the Alq3/ITO structure indicates that,as the sputtering time of argon ions beam increasing,Al2p,C1s and N1s peaks get weaker,which indicates the Alq3 film becomes thinner and thinner and the concentrations of the Al,C and N atoms reduce with increasing sputtering time.The core-levels of Al2p,C1s,N1s,O1s,In3d5/2 and Sn3d5/2 spectra slightly shift towards lower binding energy when the sputtering time increasing,this may be caused by the effect of oxygen,indium and tin in ITO diffusing into Alq3 layer and the argon ions beam with high energy.Besides these,with the sputtering time of argon ions beam increasing,the relative concentration of O atoms from ITO diffusing into Alq3 increases,and the interaction of O atoms with In and Sn atoms gradually reduces,which results in the In2O3 and SnO2 turning into suboxides or metal states In and Sn,so that the binding energy of In and Sn atoms decreases.关键词：XPS;Alq3/ITO;electronic states of surface and interface102|127|1更新时间：2020-08-11
- 摘要：The amplification of telecommunication signals near 1.5μ m has been successfully demonstrated with Er3+ doped silica fiber.However,silica fiber is unsuitable as component in short length devices because the highest possible Er3+ ion concentration in silica fiber is very low around 100ppm.There are several candidates for matrix glasses that homogeneously contain rare earth ions.Phosphate glass is one of these candi-dates.In this paper,we reported a kind of Er3+ doped phosphate glass which can be used as transmission and amplification medium in 1.5μm optical communication.The phosphate glass is composed of(mol%) P2O5(60)-Na2CO3(24)-Al2O3-Er2O3(0.5)-Yb2O3(2.0).Firstly,We precisely measured 10-gram strating materials as showed proportion,then put them into a electric-resistance furnace with temperature of 200℃ for two hours.After those unwanted vapor and gases were got rid of,we transported them into a silica-molybdenum-rod furnace with 1 200℃.When the batch was melted enough about a half hour,we quickly poured the melted liquid into a cube-shaped mould with 480℃ temperature,then put mould into electric-resistance furnace with 480℃ for anneal.The resulting glass cube was cut and polished for spectra experiments.We have measured the absorption spectrum of the galss with PERK IN-ELMER Lambda 9 spectrometer and observed eight absorption bands.Among the eight absorption bands,the absorption band near 970nm was the strongest.Th emission spectrum under 970nm LD excitation has also been acquired.In this spectrum,only a strong emission near 1540nm wavelength can be observed.We have obtained the Judd-Ofelt parameters by fitting the absorption spectrum and got the resutls as follows.Ω2=4.29×10-20(cm2);Ω4=1.01×10-20(cm2);Ω6=0.75×10-20(cm2).The spontaneous emission probabilities of the relevant transition have been calculated with the obstained Judd-Ofelt parameters,so we have a theoretic guide for researching the luminescence phenomenon in the phosphate glass.Lastly,we calculated the absorption and emission cross-section near 1.5μm by Fuchtbaure-Ladenburg theory,from the results we know that the glass has a big emission cross-section near 1.5μm emission.关键词：Er3+ doped phosphate glass;the theory of Judd-Ofelt;absorption cross-section;emission cross-section127|82|4更新时间：2020-08-11
- 摘要：Er-doped glasses have attracted much research interests due to their application in the area of optical communications,such as fiber amplifiers and lasers,and infrared solid-state lasers.To account for the optical absorption and in turn radiative properties of excited states,the Judd-Ofelt theory has been successfully applied to most of the lanthanide ions.In this paper,the experimental and theoretical oscillator strengths of some levels of Er3+ ion in Cd3Al2Si3O12 glass(CAS glass in brief) were calculated using the absorption spectra and Judd-Ofelt theory.The root-mean-square deviation is only 3.30×10-7.This result indicates that the theory is in well accord with the experiment results.Based on a least-square fit between experimental and theoretical oscillator strengths,the intensity parameters were determined.The results are Ω2=6.42×10-20cm2;Ω4=1.53×10-20cm2;Ω6=0.69×10-20cm2.Then the radiative transition proba-bility A,radiative lifetime r,branching ratio βand integrated emission cross-sections of radiative transitions of Er3+ in this glass at room temperature were calculated.According to the large integrated emission cross-emission(1.402×10-18cm) and the long lifetime(8.062ms) of the transition of 4I13/2→4I15/2 of Er3+ in CAS glass,it can be concluded 1.534μm laser oscillation of Er-doped CAS glass is possible to be demon-strated.In addition,this glass has several advantages,such as easy-made,scale-varied,easy-fibered and ad-justable host composition along with their high chemical durability and thermal stability.Therefore,Er-doped CAS glass is a potential near infrared solid-state laser material.关键词：Er3+ ions;silicate glass;absorption spectrum;J-O theory89|60|2更新时间：2020-08-11
- 摘要：Emission spectra from SrB4O7 doped with Dy2O3 and heated in air have been recorded at room temperature.A change in oxidation state from Dy3+ to Dy2+ was observed.Optimum production of Dy2+ ion occurs when the sample is heated in air at about 650℃.Two broad emission bands centered in the vicinity of 550 and 660nm have been observed from the sample under the excitation of 457.9nm.It is suggested that these bands are due to Dy2+ ion emission from the 5d band into the ground state 4f level(5I8).Several conditions promoting the reduction of Dy3+ ion in this matrix are discussed.To aid the reduction of Dy3+ ion,we have also prepared SrB4O7 doped with Dy2O3 in Ar/H2(4%) atmosphere and compared the optical characteristics of Dy2+ ion in these samples with those from the samples prepared in air.The range of g-element reducibility and stabilization in SrB4O7 has been extended from Tm2+ [E0(Tm3+/Tm2+)=-2.3V] to Dy2+ [E0(Dy3+/Dy2+)=-2.6V] in the present work;however,the limit of this facile reduction process has not been determined yet.关键词：luminescence of rare earth;divalent dysprosium;SrB4O7115|119|0更新时间：2020-08-11
- 摘要：Luminescent films have found extensive applications in flat panel display devices,which have advantages such as higher contrast and resolution,better thermal stability,superior thermal conductivity,a high degree of uniformity and better adhesion to the substrate as well as a reduced outgassing rate.In this paper,based on our research owrk,a review has been given on the basic processes,characterization methods,and current development and application situation for luminescent films fabricated by sol-gel method.Classified by compositions,the sol-gel derived luminescent films include inorganic luminescent films and organic/inorganic hybrid luminescent films,whose photoluminescent,cathodoluminescent,electroluminescent and field emission properties have been widely studied.Besides the silicate phosphor films which mainly employed alkoxysilanes as the main precursors for sol-gel transition,we also prepared other important phosphor films such as vanadates doped with rare earth ions by Pechini sol-gel process using inorganic salts as precursors,and realized the patterning of the phosphor films by soft lithography( micro-molding in capillaries).Finally,the future development tendency for the luminescent films are forecasted.关键词：sol-gel process;luminescence;film128|162|0更新时间：2020-08-11
- 摘要：Trivalent erbium doped glasses are attracting extensive interest due to its potential application in various optical devices such as optical communication,display and lasers.In this paper,the preparation and the infrared luminescent properties of some erbium doped oxide glasses were reported.High erbium doped three multicomponent oxide glasses,B2O3-SiO2,Al2O3-SiO2 and Li2O3-Al2O3-SiO2 were fabricated by the technique of high-temperature melting.The infrared emission spectra of erbium in the glasses were measured under the excitation of a 488nm argon ion laser.The influence of the host composition and the erbium-concentration on infrared luminescent property at 1.5μm was studied.The results indicate that the emission in-tensity varies remarkably in different hosts.Among the glasses,the emission of erbium in the B2O3-SiO2 glass is strongest,while that in the Al2O3-SiO2-CdO glass is the weakest.In addition,the emission intensity of B2O3-SiO2 glass doped with erbium increases almost linearly with the erbium concentration,which is favorable for luminous material.In all the glasses,the emission intensity at 1.5μm increases with the erbium concentration,indicating that the concentration-quenching effect is small as the erbium concentration is lower than 2wt%.Among the three glasses,the Er3+ Li2O-Al2O3-SiO2 one has a widest emission band at 1.5μm.The global line width of erbium in this glass is as wide as 61.1nm due to the disordered local struc-ture surrounding the erbium ions.Therefore,it is expected to be a deal glass for optical waveguide amplifiers.By contrast to the components of the three glasses,it can be concluded that the global line width of erbium is probably broadened due to the co-doping of Li2O in the Al2O3-SiO2 glass,although the detail origin is not clear.关键词：Er3+ ion;oxide glass;spectroscopy94|58|3更新时间：2020-08-11
- 摘要：Recently,the neodymium-doped crystal Nd3+ KGd(WO4)2,(or Nd:KWG) lasing at 1067nm was demonstrated that it exhibits highly efficient free-running operation.The laser crystal also possesses other attractive features,such as a strong and broad absorption band that makes this laser medium be an ex-cellent candidate for efficient diode pumping without temperature controlling.The absorption band at 0.8μm of Nd3+ in the crystal is well matched with the emission wavelength of diode,a solid state laser pump which is very convenient and popular in laser science and technology today.Nd:KWG crystal was grown by the TSSG slow cooling method from a suitable flux K2W2O7.TG-DTA tests show Nd:KWG(5at%) crystal has a phase transition at 984℃,which is below the melting point 1044℃.The lower value compared with pure KGW can be explained by the doping of Nd3+ XFA shows the existence of element of W,K,Gd,O,Nd.And the intensities agree with the proportion of raw materials.In IR and Raman spectra,it can be observed that the Ln-O vibration transitions are at 400.4cm-1,408cm-1,atom group WO4 flex vibration at 344.8~429cm-1 and atom group WO4 bend vibration at 750~ 899.5cm-1.The absorption spectrum of Nd:KWG crystal was measured.It should be noted that there is a strong absorption band at 808nm,the emission wavelength of the laser diode.And,we also calculated the absorption cross sections.关键词：Nd:KWG;laser crystal;TSSG;spectra105|78|2更新时间：2020-08-11
- 摘要：The relationship between spectral properties and local structure of Eu3+ in AlF3-based fluoride glasses was studied.The phonon sideband was measured in order to get the information about the phonon mode coupled to the rare-earth ions.Moreover,the coordination states was discussed from the isomer shift of 151Eu3+ ions in ABCE glass.According to the emission spectra and the analysis of symmetrically equiva-lent points in space group,it is inferred by symmetry breaking that the Eu3+ ions in ABCE glass must be mainly located at the S6 and Ci site symmetry.关键词：fluoride glass;spectral properties;local structure95|60|0更新时间：2020-08-11
- 摘要：A new fluride-oxide vitroceramics GeO2-NaF-BaF2(MFG) for up-conversion luminescence was reported.X-ray diffraction spectra and Raman spectra of MFG vitroceramic were measured.The results confirm that there exist many cubic-BaF2 nanocrystals in MFG vitroceramic and the phonon energy of cubic-BaF2 nanocrystals is about 152cm-1.Infrared emission spectrum(λex=488nm) and up-conversion emission spectrum of Tm3+ and Er3+ co-doped MFG samples were also measured.Several proofs on RE ions enriched nanocrystals were presented.In the end,we discussed the effects of nanocrystal-phase structure on red up-conversion luminescence.121|58|3更新时间：2020-08-11
- 摘要：Molecular aggregates are mesoscopic clusters of molecules,with intermediate sizes between crystals and isolated molecules.Molecular aggregates belong to the group of nanostructure materials,which are presently at the heart of scientific fashion.In particular the unique optical properties of these materials receive much attention.An important difference between aggregates and most other nanostructures is the absence of electron delocalization,which makes its optical response easier to model.The red shift and narrowing for J-band were observed from the absorption spectrum of molecular aggregates PIG-I in this paper.The number of monomers in the chain N≈3,or chain length L=0.3nm×3=0.9nm were calculated,and vibration mode 1368cm-1 was derived from the experimental data.Com-paring the fluorescence spectrum with the absorption spectrum it is found that the emission band 572.5nm and absorption band 572.5nm is resonance.Raman spectra(100~1800cm-1) of molecular aggregates PIC-I were systematically investigated.关键词：organic nanomaterial;molecular aggregate;Raman spectrum96|81|0更新时间：2020-08-11
- 摘要：The four kinds of films MEH-PPV(1mg)/ml,[MEH-PPV(1mg)+TiO2(1mg)]/ml,[MEH-PPV(1mg)+TiO2(2mg)]/ml and [MEH-PPV( 1mg)+TiO2(3mg)]/ml were made by dip coating method.The diameters of the scatters TiO2 are of submicrometer in all reports published before in films or solutions.Random lasing with the scatters of 20nm has been reported in this letter.The femtosecond laser through OPA hamornics produce 130fs pulse duration,544nm exciting wavelength,1kHz repeat ratio,and 3~μJ/pulse pump power.The spectrum line narrowed dramatically almost in two orders of magnitude,smaller than the spectrum lines excited by Xenon lampe.The outputs on the end of the film were exponen-tially increased with lengthening the excitation stripe of laser beam.It is shown that the amplified sponta-neous emission(ASE) is the dominant mechanism.The effects of Anderson location of light on random las-ing with the mean free path l=5.4×105nm were discussed.关键词：random microcavity;lasing of polymer;localization of light110|72|0更新时间：2020-08-11
- 摘要：The LB method is usually used to fabricate highly ordered ultrathin films of various organic sub-stance based on amphiphyllic molecules.Now the LB technique is used to made some of oxide thin films.The metal carboxylate films were constructed by LB technique and used as precursors.The organic component was removed to form metal oxide films by directly heating the LB films or exposing the LB films to ultraviolet light and reactive oxygen.In this paper we constructed Eu-doped yttrium arachidate LB film us-ing YCl3 and EuCl3 aqueous as subphase.The π-A isotherm indicated that the arachidic acid had good film-forming ability on the YC13 aqueous subphase,the monolayer collapse pressure was about 53mN/m.The monolayer on the surface of YCl3 aqueous was successfully transferred onto different substrates such as mica,silicon wafer,quartz and so on.The AFM image exhibited the uniformity of the transferred mono-layer.The IR spectrum and the X-ray photoelectron spectrum confirmed that the arachidic acid reacted with YCl3 and formed yttrium arachidate.From the emission spectrum,the luminescence of Eu3+ was ob-served.These results indicated that the Eu-doped yttrium arachidate LB film was constructed successfully and some treatment could be completed to make Y2O3 Eu thin film.100|82|0更新时间：2020-08-11
- 摘要：LaPO4:Ce,Tb was an important green luminescence material used in tricolour fluorescent lamp.It could replace the(Ce,Tb) MgAl11O19 phosphor used in the China.The main synthesis method of the phosphor was the high temperature solid state method.The phosphor had a great particle size.It must be milled when it was used.This way not only increased production cost,but also influenced on luminescence intensity.(La,Ca,Tb)PO4 was prepared by coprecipitation of a rare earth nitrate solution with diammonium hydrogen phosphate as precipitation agent while adding little surfactant and controlling the conditions of the reaction.The green-emitting phosphor LaPO4:Ce,Tb used in fluorescent lamps was prepared by it as the precursors.The most suitable technological conditions were obtained.RE(NO3)3 and(NH4)2HPO4 were si multaneously added at the same rate in the experiment.The concentrations of RE(NO3)3 and(NH4)2HPO4 should be the same in order to ensure a uniform precipitation.The suitable concentration of the feed liquid is 0.2mol/L.The suitable reaction temperature was controlled to be 30~40℃ in the experiment.The crystal size of(La,Ce,Tb) PO4 in precipitation and its property of filtre were improved by adding a little surfacetant.The precipitation and mother liquid were aged for a period with a pH value of 7 usually.The suitable aging time is 1-2h,and the suitable aging temperature was determined to be 50-60℃.The most suitable calcination temperature of the phosphor is 900℃ and calcination time is 1h under the carbon-reducing atmosphere.The partical size of the LaPO4:Ce,Tb fluorescent powder prepared in present experiment was mea-sured by a laser granularity meter:D50=4.34μm.The particle is fine and the granularity displays a narrow normal distribution which can meet the needs of fluorescent lamp fabrication.The X-ray diffraction spec-trum clearly shows that the fluorescent powder has a phosphatic monoclinic monazete structure without any impurity phase and the structure didn't change after adding H3BO3.The phosphor LaPO4:Ce,Tb was mea-sured by PMS-3 chromatic detector,and its luminescent chromatic coordinate parameters are:x=0.347 4,y=0.758 4,the colour rending index is Ra=22.5.The phosphor had high luminescence intensity which was equal to that of the(Ce,Tb) MgAl11O19 phosphor in market.The phosphor LaPO4:Ce,Tb prepared by coprecipitation had higher luminescence lightness,finer particle and lower calcinations temperature than that prepared by the high temperature solid state method.The coprecipitation method become possible synthesis ways of non-grinding green fluorescent powder of phosphate.关键词：coprecipitation;no-grinding;phosphate;phosphor92|77|6更新时间：2020-08-11
- 摘要：Using benzoic acid gas,we fabricated proton-exchanged planar waveguide layer in z-cut LiTaO3 surface.'The preparations of the samples are as follows:First,waveguides layer was fabricated in the-c and+c face of LiTaO3 substrates in benzoic acid gas at 245℃ for 8~20h.The proton-exchanged layers were formed in the face of LiTaO3.Then the samples of waveguide were measured by prism coupling method.After that,waveguide layer in the surface of LiTaO3 was etched in HF:HNO3 acid and then measusured by use of electronic microscope.Using chemical etch method,we observed waveguide layer and the shape and form of inner interface of waveguides.Using X-ray diffraction method,we measured the change of lattice constant of proton-exchanged waveguide.The double crystal X-ray diffraction rocking curves analysis was used to determine the lattice constants of the proton-exchanged(PE) and annealed proton-exchanged(APE) 1ayer.The X-ray diffrac-tion rocking curves of the sample show that the rate of the lattice constant changes of the PE and APE were different.The lattice constants of the LiTaO3 substrates without and with the domain-inverted slab struc-ture were measured.The experimentaI results were reported and discussed in detail.关键词：proton-exchanged waveguide;LiTaO3;lattice constant96|82|0更新时间：2020-08-11
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