Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interfere...Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interference between the defect states. Therefore, the designed double defect modes in the zero effective-phase gap can be adjusted independently by changing the thickness of different defect layers. In addition, the two tunable defect modes have the omnidirectional characteristics. This multi-defect structure with above-mentioned two advantages has potential applications in modern optical devices such as tunable omnidirectional filters.展开更多
By means of the transfer-matrix method, the effects of parameter modulation on the quafity of near-field imaging in one-dimensional photonic crystal consisting of alternately left-handed material and right-handed mate...By means of the transfer-matrix method, the effects of parameter modulation on the quafity of near-field imaging in one-dimensional photonic crystal consisting of alternately left-handed material and right-handed material are investigated. Based on analyses of the recovery rate and ph＇ase shift, the results show that the imaging quality is not obviously affected by the minor changes of layer thickness. In addition, by modulating the material parameters of the left-handed material, it is found that for both the real part and the imaginary part, the system is more sensitive to the permeability than the permittivity for the TE wave. For the TM wave, it is reverse. These properties are very useful to fabricate left-handed material photonic crystals in practice.展开更多
Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.T...Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.The nontoxic cerium-doped lead-free perovskites with intrinsically efficient and short lifetime d–f transitions are a prospective replacement for the toxic Pb^(2+).Here,we demonstrated Ce-doped cesium lanthanide chloride perovskites (Cs_(3)LnCl_(6),Ln=Gd,Y,Lu) synthesized through a facile solution method for the first time.These perovskites exhibit blue-violet emission,which arises from Ce 5d→4f transitions.Among three types of Cs_(3)LnCl_(6) perovskites,Ce:Cs_(3)LuCl_(6) exhibited high photoluminescence quantum yield (PLQY) of 82%and a short excited-state lifetime of approximately 34 ns.When utilized as X-ray scintillators,Ce:Cs_(3)LuCl_(6) crystals display a high light yield of 8120 photons per MeV and a low detection limit of 36.8 n Gy air s^(-1).Importantly,the figure of merit (FoM),representing the ratio of light yield to decay time,reaches 239,which is the highest reported value for lead-free perovskite scintillators up to now.Additionally,the fabrication of perovskite/PMMA films was undertaken for practical demonstrations in X-ray imaging,resulting in the attainment of a resolution of up to 8.38 lp/mm.We anticipate that this work will inspire the utilization of Ce-doped Cs_(3)LnCl_(6) perovskites in ultrafast scintillation applications such as high-energy physics,nuclear reaction monitoring,and dynamic X-ray imaging.展开更多
A novel fiber Bragg grating (FBG) current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam,which has a step thickness alo...A novel fiber Bragg grating (FBG) current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam,which has a step thickness along the beam axis. Due to the electromagnetic force created by a solenoid and a permanent magnet mounted on the top of the beam,a step strain is applied on the fiber Bragg grating. The change of the electric current in the solenoid makes the spectrum of the fiber Bragg grating split. By monitoring the shift difference of the two split center wavelengths,which is related to the electric current in the solenoid,a current sensor with temperature compensation is obtained. The test range of 0-400 mA is achieved. The experimental results also show that the relationship between the shift difference of the two split center wavelengths of the FBG and the electric current has a linearity of 0.9937,and the sensitivity is about 2.64 nm/A; the test results are independent of the temperature,so the cross sensitive problem is solved.展开更多
We use the label-free microsphere-assisted microscopy to image low-contrast hexagonally close-packed polystyrene nanoparticle arrays with diameters of 300 and 250 nm.When a nanoparticle array is directly placed on a g...We use the label-free microsphere-assisted microscopy to image low-contrast hexagonally close-packed polystyrene nanoparticle arrays with diameters of 300 and 250 nm.When a nanoparticle array is directly placed on a glass slide,it cannot be distinguished.If a 30-nm-thick Ag film is deposited on the surface of a nanoparticle array,the nanoparticle array with nanoparticle diameters of 300 and 250 nm can be distinguished.In addition,the Talbot effect of the 300-nm-diameter nanoparticle array is also observed.If a nanoparticle sample is assembled on a glass slide deposited with a 30-nm-thick Ag film,an array of 300-nm-diameter nanoparticles can be discerned.We propose that in microsphere-assisted microscopy imaging,the resolution can be improved by the excitation of surface plasmon polaritons(SPPs) on the sample surface or at the sample/substrate interface,and a higher near-field intensity due to the excited SPPs would benefit the resolution improvement.Our study of label-free super-resolution imaging of low-contrast objects will promote the applications of microsphere-assisted microscopy in life sciences.展开更多
The spectra of fiber Bragg grating (FBG) in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method ...The spectra of fiber Bragg grating (FBG) in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method can be employed for exact simulation of the spectrum of Bragg grating in such field, but the convergence speed is slow. On the other hand, although the transfer matrix method could be used with higher convergence speed, the precision is poor because of the neglect of the grads of strain change. By improving the FBG equivalent period, a novel simulation method based on a modified transfer matrix method is proposed, which has the advantage of quick-convergence as well as good accuracy.展开更多
A symmetrical π-shaped metamaterial is investigated. Numerical simulations exhibit the negative-refractive property of this structure. The complex refractive index n, wave impedance z, effective permittivity ε and e...A symmetrical π-shaped metamaterial is investigated. Numerical simulations exhibit the negative-refractive property of this structure. The complex refractive index n, wave impedance z, effective permittivity ε and effective permeability μ have been retrieved from the simulated S parameters. The negative-refractive band lies between 11.2 GHz and 13.05 GHz. The frequency band with high transmission with low loss occurs between 11.95 GHz and 12.5 GHz, which is helpful for practical applications. The mechanism of the electromagnetic resonance is also revealed.展开更多
Two tribranched chromophores,1,3,5-triazine as electron deficient core,9,9-dimethylfluorene asπ-conjugated bridge, diphenylamino（4a） and naphthylamino（4b） as electron-donating end-groups,were successfully prepare...Two tribranched chromophores,1,3,5-triazine as electron deficient core,9,9-dimethylfluorene asπ-conjugated bridge, diphenylamino（4a） and naphthylamino（4b） as electron-donating end-groups,were successfully prepared via Buchwald-Hartwig coupling reaction.Their linear photophysical and two-photon absorption（TPA） properties were investigated by absorption, fluorescence and nonlinear transmission method,respectively.The absorption cut-offs of the chromophores are below 550 nm and both chromophores have strong fluorescence emission.The compound 4a（206.3 GM） exhibits larger TPA cross-section than 4b （57.8 GM） in the femtosecond regime at 800 nm.展开更多
Second harmonic generation （SHG） of a new organic optical crystal-urea L-malic acid （ULMA） was studied. A comparison of SHG efficiency of ULMA and KDP at a fundamental wavelength of 1064 nm using the Kurtz powder ...Second harmonic generation （SHG） of a new organic optical crystal-urea L-malic acid （ULMA） was studied. A comparison of SHG efficiency of ULMA and KDP at a fundamental wavelength of 1064 nm using the Kurtz powder method demonstrated that the second order nonlinear coefficient of ULMA is 1 57 times of that of KDP,and the damage threshold of ULMA is relatively higher Finally,both Type Ⅰ and Type Ⅱ phase match angles of the biaxial crystal ULMA were calculated.展开更多
Well-crystallized MgZnO alloy thin films with hexagonal wurtzite structure were fabricated by sol-gel method. With the band gap increases, the surface roughness and the grain size reduces. It is worth noting that the ...Well-crystallized MgZnO alloy thin films with hexagonal wurtzite structure were fabricated by sol-gel method. With the band gap increases, the surface roughness and the grain size reduces. It is worth noting that the intensity of the band-edge luminescence of Mg doped films enhances with the increase of the Mg content. The microstructure and photoluminescence mechanism have been discussed based on X-ray diffraction patterns, atomic force microscopy images, ultraviolet-visible absorption spectra, photoluminescence spectra and Fourier transform infrared spectra.展开更多
Employing an organic dye salt of trans-4-[p-[N-methyl-N-（hydroxymethyl）amino]styryl]-N-methylphridinium tetraphenylbovate （ASPT） as the active layer, 8-hydrocyquinoline aluminium （Alq3） as the electron transport...Employing an organic dye salt of trans-4-[p-[N-methyl-N-（hydroxymethyl）amino]styryl]-N-methylphridinium tetraphenylbovate （ASPT） as the active layer, 8-hydrocyquinoline aluminium （Alq3） as the electron transporting layer and N, N＇-diphenyl-N, N＇-bis（3-methylphenyl）-[1,1＇-biphenyl]-4,4＇-diamine （TPD） as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence （EL）. The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region.展开更多
ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmissi...ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmission electron microscopy. The ZnO nanorods exhibit single crystals with the hexagonal wurtzite structure. Many of them are tetrapod-like. The diameters range from several nanometres to about lOOnm, and the main diameters of the nanorods is around 20nm. The length-to-diameter ratio is more than 5, and the grown directions are along the [001] axis. Photoluminescence spectra show a narrow ultraviolet emission at around 389nm and a broad green emission at around 520 nm. The growth process can be interpreted by the vapour-solid mechanism.展开更多
A pioneering glass-compatible transparent temperature alarm system self-powered by luminescent solar concentrators(LSCs) is reported.Single green-emitted organic manganese halides(OMHs) of PEA_(2)MnBr_(2)I_(2),which h...A pioneering glass-compatible transparent temperature alarm system self-powered by luminescent solar concentrators(LSCs) is reported.Single green-emitted organic manganese halides(OMHs) of PEA_(2)MnBr_(2)I_(2),which has a unique temperature-dependent backward energy transfer process from selftrapped state to^(4)T_(1)energy level of Mn,is used for triggering the temperature alarm.The LSC with redemitted CsPbI_(3)perovskite-polymer composite films on the glass substrate is used for power supply.The spectrally separated nature between the green-emitted OMHs for temperature alarm and red-emitted CsPbI3in LSC for power supply allows for probing the signal light of temperature-responsive OMHs without the interference of LSCs,making it possible to calibrate the temperature visually just by a self-powered brightness detection circuit with LED indicators.Taking advantage of LSC without hot spot effects plaguing the solar cells,as-prepared temperature alarm system can operate well on both sunny and cloudy day.展开更多
The donor-acceptor complex derived from 2-amino-1,3-benzothiazole （ABT） and ethyl 5,6-benzocoumarin-3-carboxylate （EBCC） has been synthesized and its crystal structure was determined by single-crystal X-ray diffra...The donor-acceptor complex derived from 2-amino-1,3-benzothiazole （ABT） and ethyl 5,6-benzocoumarin-3-carboxylate （EBCC） has been synthesized and its crystal structure was determined by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/c, with a = 8.6485（3）, b = 7.7743（3）, c = 29.1963（10） A, β = 92.0460（10）°, Z = 4, Mr = 418.45, V= 1961.79（12） A^3, Dc = 1.417 g/cm^3,μ = 0.199 mm^-1, F（000） = 872, the final R = 0.0350 and wR = 0.1226. The complex is an A…D…D＇…A＇ H-bonded tetramer. The intermolecular N-H…O and N-H…N hydrogen bonds, together with π-π stacking interactions, stabilize the crystal structure by forming a supramolecular architecture. It is found that, in solid state, the fluorescence emission of the complex is quenched significantly while the UV-vis spectrum exhibits a broad band at 346 nm with shoulder, which can be attributed to the donor-acceptor complex formed.展开更多
Three-photon absorption（3PA） of a push-pull chromophore,2-（3-cyano-（3-（4-（dimethylamino）styryl）-5,5-dimethylcyclohex- 2-enylidene）methyl）-5,5-dimethylfuran-2-ylidene） malononitrile（CFM） including TCF grou...Three-photon absorption（3PA） of a push-pull chromophore,2-（3-cyano-（3-（4-（dimethylamino）styryl）-5,5-dimethylcyclohex- 2-enylidene）methyl）-5,5-dimethylfuran-2-ylidene） malononitrile（CFM） including TCF group was measured by the nonlinear transmission method using a femto-second Ti：Sapphire oscillator-amplifier laser system.Its three-photon absorption cross-sections at 1300 ran were 36.8×10^-79 cm^6 s^2 in the solution of DMF and 12.3×10^-79 cm^6 s^2 in the solution of CH_2Cl_2,respectively.The large values were got by experiments in this paper,which is a new exploration for these kinds of materials.The molecule has the potential application foreground of 3PA areas and optical power limiting.展开更多
ZnO is introduced as an alternative to TiO2 in dye sensitized solar cells （DSSCs） due to its band gap similar to TiO2, higher electron mobility, and flexible procedures of preparations. Several samples of ZnO films ...ZnO is introduced as an alternative to TiO2 in dye sensitized solar cells （DSSCs） due to its band gap similar to TiO2, higher electron mobility, and flexible procedures of preparations. Several samples of ZnO films are prepared with the hydrothermal synthesis method and the sol-gel technique, respectively. These ZnO films were assembled as photoanodes in DSSCs using N3 dye as the sensitizer. The ZnO-based cells prepared by the hydrothermal synthesis show typical current source characteristics, whose fill factor （FF） is 0.44 and photo-to-electric power conversion efficiency is 0.34%. On the other hand, all the samples prepared with the sol-gel technique show accompanied source characteristics with relatively higher power conversion efficiencies （1%） but a lower FF （0.26）. X-ray diffraction （XRD） and atomic force microscopy （AFM） measurements indicate that the sol-gel samples have small particles sizes. Therefore, sol-gel samples could adsorb more dye molecules to generate high conversion efficiencies. At the same time, more grain boundaries make it more possible for injected electrons to recombine with the oxidized electrolyte. Hydrothermal samples have bigger grains, so they show poor conversion efficiency and relatively high FF.展开更多
A novel octupolar chromophore with 1,3,5-triazine as core,2,7-divinylene-9,9-dimethylfluorene as extendedπ-conjugated bridge,triarylamine as the electron-donating end-groups was successfully synthesized and character...A novel octupolar chromophore with 1,3,5-triazine as core,2,7-divinylene-9,9-dimethylfluorene as extendedπ-conjugated bridge,triarylamine as the electron-donating end-groups was successfully synthesized and characterized.Their linear photophysical and two-photon absorption（TPA） properties were investigated by UV absorption,excited fluorescence（SPEF） spectra and nonlinear transmission method,respectively.The absorption cut-off of the chromophore is below 520 nm and it has stronger fluorescence emission in a nonpolar solvent.In addition,the chromophore exhibits larger TPA cross-section（226.0 GM） in the femtosecond regime at 800 nm.展开更多
Strong second-order nonlinear effect of ZnO nanowires on a silicon wafer are demonstrated by using the hyper- Rayleigh scattering （FIRS） measurement. The large nonlinear effect can be attributed to the following two...Strong second-order nonlinear effect of ZnO nanowires on a silicon wafer are demonstrated by using the hyper- Rayleigh scattering （FIRS） measurement. The large nonlinear effect can be attributed to the following two factors： （1） the large total dipole moment caused by high surface defect density and electrostatic potential gradient, （2） coherent effect due to high crystal quality of single nanowire. Moreover, the second-order nonlinear effect is found to become weaker when the chip is put into organic solvent due to modification of surface defect caused by organic molecules. The variation of second-order signal in the solvent indicated the potential applications of ZnO nanowires as a sensor-on-chip （SoC）.展开更多
We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula off...We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes.展开更多
An organic dye salt trans-4-[p-（N-hydroxyethyl-N-methylamino）styryl]-N-methylpyridinium iodide （ASPI） is doped with an electron transport organic molecule tris（8-hydroxyquinoline） aluminium （Alq3） in a host ma...An organic dye salt trans-4-[p-（N-hydroxyethyl-N-methylamino）styryl]-N-methylpyridinium iodide （ASPI） is doped with an electron transport organic molecule tris（8-hydroxyquinoline） aluminium （Alq3） in a host matrix of poly（methylmethacrylate） （PMMA）, and the amplified spontaneous emission （ASE） is studied. By efficient Forster energy transfer from Alq3 to ASPI, it is demonstrated that the ASE threshold of ASPI：Alq3：PMMA waveguide （about 11 μJ/pulse） is much lower than that of ASPI：PMMA system （about 38 μJ/pulse）. Meanwhile, the peak position of ASE can be controlled by the effect of film thickness on waveguide modes. We show that the ASE peak position can be tuned over 37nm. These characteristics indicate the ASPI：Alq3 system as a promising gain medium for optical amplifiers and organic semiconductor lasers.展开更多
文摘Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interference between the defect states. Therefore, the designed double defect modes in the zero effective-phase gap can be adjusted independently by changing the thickness of different defect layers. In addition, the two tunable defect modes have the omnidirectional characteristics. This multi-defect structure with above-mentioned two advantages has potential applications in modern optical devices such as tunable omnidirectional filters.
文摘By means of the transfer-matrix method, the effects of parameter modulation on the quafity of near-field imaging in one-dimensional photonic crystal consisting of alternately left-handed material and right-handed material are investigated. Based on analyses of the recovery rate and ph＇ase shift, the results show that the imaging quality is not obviously affected by the minor changes of layer thickness. In addition, by modulating the material parameters of the left-handed material, it is found that for both the real part and the imaginary part, the system is more sensitive to the permeability than the permittivity for the TE wave. For the TM wave, it is reverse. These properties are very useful to fabricate left-handed material photonic crystals in practice.
基金supported by the National Natural Science Foundation of China (Grant Nos. 22075043, 21875034, 12274075, 62375142)。
文摘Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.The nontoxic cerium-doped lead-free perovskites with intrinsically efficient and short lifetime d–f transitions are a prospective replacement for the toxic Pb^(2+).Here,we demonstrated Ce-doped cesium lanthanide chloride perovskites (Cs_(3)LnCl_(6),Ln=Gd,Y,Lu) synthesized through a facile solution method for the first time.These perovskites exhibit blue-violet emission,which arises from Ce 5d→4f transitions.Among three types of Cs_(3)LnCl_(6) perovskites,Ce:Cs_(3)LuCl_(6) exhibited high photoluminescence quantum yield (PLQY) of 82%and a short excited-state lifetime of approximately 34 ns.When utilized as X-ray scintillators,Ce:Cs_(3)LuCl_(6) crystals display a high light yield of 8120 photons per MeV and a low detection limit of 36.8 n Gy air s^(-1).Importantly,the figure of merit (FoM),representing the ratio of light yield to decay time,reaches 239,which is the highest reported value for lead-free perovskite scintillators up to now.Additionally,the fabrication of perovskite/PMMA films was undertaken for practical demonstrations in X-ray imaging,resulting in the attainment of a resolution of up to 8.38 lp/mm.We anticipate that this work will inspire the utilization of Ce-doped Cs_(3)LnCl_(6) perovskites in ultrafast scintillation applications such as high-energy physics,nuclear reaction monitoring,and dynamic X-ray imaging.
文摘A novel fiber Bragg grating (FBG) current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam,which has a step thickness along the beam axis. Due to the electromagnetic force created by a solenoid and a permanent magnet mounted on the top of the beam,a step strain is applied on the fiber Bragg grating. The change of the electric current in the solenoid makes the spectrum of the fiber Bragg grating split. By monitoring the shift difference of the two split center wavelengths,which is related to the electric current in the solenoid,a current sensor with temperature compensation is obtained. The test range of 0-400 mA is achieved. The experimental results also show that the relationship between the shift difference of the two split center wavelengths of the FBG and the electric current has a linearity of 0.9937,and the sensitivity is about 2.64 nm/A; the test results are independent of the temperature,so the cross sensitive problem is solved.
基金Project supported by the National Natural Science Foundation of China(Grant No.61673287)。
文摘We use the label-free microsphere-assisted microscopy to image low-contrast hexagonally close-packed polystyrene nanoparticle arrays with diameters of 300 and 250 nm.When a nanoparticle array is directly placed on a glass slide,it cannot be distinguished.If a 30-nm-thick Ag film is deposited on the surface of a nanoparticle array,the nanoparticle array with nanoparticle diameters of 300 and 250 nm can be distinguished.In addition,the Talbot effect of the 300-nm-diameter nanoparticle array is also observed.If a nanoparticle sample is assembled on a glass slide deposited with a 30-nm-thick Ag film,an array of 300-nm-diameter nanoparticles can be discerned.We propose that in microsphere-assisted microscopy imaging,the resolution can be improved by the excitation of surface plasmon polaritons(SPPs) on the sample surface or at the sample/substrate interface,and a higher near-field intensity due to the excited SPPs would benefit the resolution improvement.Our study of label-free super-resolution imaging of low-contrast objects will promote the applications of microsphere-assisted microscopy in life sciences.
基金This workis supported by Jiangsu Province Natural Science Fou-ndation of China under project BK2004207 the National Sci-ence Fund for Distinguished Young Scholars under project60125513 .
文摘The spectra of fiber Bragg grating (FBG) in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method can be employed for exact simulation of the spectrum of Bragg grating in such field, but the convergence speed is slow. On the other hand, although the transfer matrix method could be used with higher convergence speed, the precision is poor because of the neglect of the grads of strain change. By improving the FBG equivalent period, a novel simulation method based on a modified transfer matrix method is proposed, which has the advantage of quick-convergence as well as good accuracy.
文摘A symmetrical π-shaped metamaterial is investigated. Numerical simulations exhibit the negative-refractive property of this structure. The complex refractive index n, wave impedance z, effective permittivity ε and effective permeability μ have been retrieved from the simulated S parameters. The negative-refractive band lies between 11.2 GHz and 13.05 GHz. The frequency band with high transmission with low loss occurs between 11.95 GHz and 12.5 GHz, which is helpful for practical applications. The mechanism of the electromagnetic resonance is also revealed.
基金supported financially by National Natural Science Foundation of China(Nos.20774039 and 20872061)the National Basic Research(No.2007CB925103)
文摘Two tribranched chromophores,1,3,5-triazine as electron deficient core,9,9-dimethylfluorene asπ-conjugated bridge, diphenylamino（4a） and naphthylamino（4b） as electron-donating end-groups,were successfully prepared via Buchwald-Hartwig coupling reaction.Their linear photophysical and two-photon absorption（TPA） properties were investigated by absorption, fluorescence and nonlinear transmission method,respectively.The absorption cut-offs of the chromophores are below 550 nm and both chromophores have strong fluorescence emission.The compound 4a（206.3 GM） exhibits larger TPA cross-section than 4b （57.8 GM） in the femtosecond regime at 800 nm.
文摘Second harmonic generation （SHG） of a new organic optical crystal-urea L-malic acid （ULMA） was studied. A comparison of SHG efficiency of ULMA and KDP at a fundamental wavelength of 1064 nm using the Kurtz powder method demonstrated that the second order nonlinear coefficient of ULMA is 1 57 times of that of KDP,and the damage threshold of ULMA is relatively higher Finally,both Type Ⅰ and Type Ⅱ phase match angles of the biaxial crystal ULMA were calculated.
基金supported by the National Natural Science Foundation of China(Nos.10674023 and 60725413)863 Program(No.2006AA03Z313)+1 种基金973 Program(No.2007CB936300)the NSFJ(No.BK2006090)
文摘Well-crystallized MgZnO alloy thin films with hexagonal wurtzite structure were fabricated by sol-gel method. With the band gap increases, the surface roughness and the grain size reduces. It is worth noting that the intensity of the band-edge luminescence of Mg doped films enhances with the increase of the Mg content. The microstructure and photoluminescence mechanism have been discussed based on X-ray diffraction patterns, atomic force microscopy images, ultraviolet-visible absorption spectra, photoluminescence spectra and Fourier transform infrared spectra.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60125513, 10474010, and 10274009, and the Jiangsu High-Technology Program under Grant No BG2003032.
文摘Employing an organic dye salt of trans-4-[p-[N-methyl-N-（hydroxymethyl）amino]styryl]-N-methylphridinium tetraphenylbovate （ASPT） as the active layer, 8-hydrocyquinoline aluminium （Alq3） as the electron transporting layer and N, N＇-diphenyl-N, N＇-bis（3-methylphenyl）-[1,1＇-biphenyl]-4,4＇-diamine （TPD） as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence （EL）. The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region.
基金Supported by the National Natural Science Foundation of China under Grant No 60576008, and the Doctoral Programme High Education （20050286004）.
文摘ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmission electron microscopy. The ZnO nanorods exhibit single crystals with the hexagonal wurtzite structure. Many of them are tetrapod-like. The diameters range from several nanometres to about lOOnm, and the main diameters of the nanorods is around 20nm. The length-to-diameter ratio is more than 5, and the grown directions are along the [001] axis. Photoluminescence spectra show a narrow ultraviolet emission at around 389nm and a broad green emission at around 520 nm. The growth process can be interpreted by the vapour-solid mechanism.
基金supported by the Natural Science Foundation of China(22075043,21875034,61704093)。
文摘A pioneering glass-compatible transparent temperature alarm system self-powered by luminescent solar concentrators(LSCs) is reported.Single green-emitted organic manganese halides(OMHs) of PEA_(2)MnBr_(2)I_(2),which has a unique temperature-dependent backward energy transfer process from selftrapped state to^(4)T_(1)energy level of Mn,is used for triggering the temperature alarm.The LSC with redemitted CsPbI_(3)perovskite-polymer composite films on the glass substrate is used for power supply.The spectrally separated nature between the green-emitted OMHs for temperature alarm and red-emitted CsPbI3in LSC for power supply allows for probing the signal light of temperature-responsive OMHs without the interference of LSCs,making it possible to calibrate the temperature visually just by a self-powered brightness detection circuit with LED indicators.Taking advantage of LSC without hot spot effects plaguing the solar cells,as-prepared temperature alarm system can operate well on both sunny and cloudy day.
基金supported by the Jiangsu Planned Projects for Postdoctoral Research Funds (No. 0701001B)
文摘The donor-acceptor complex derived from 2-amino-1,3-benzothiazole （ABT） and ethyl 5,6-benzocoumarin-3-carboxylate （EBCC） has been synthesized and its crystal structure was determined by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/c, with a = 8.6485（3）, b = 7.7743（3）, c = 29.1963（10） A, β = 92.0460（10）°, Z = 4, Mr = 418.45, V= 1961.79（12） A^3, Dc = 1.417 g/cm^3,μ = 0.199 mm^-1, F（000） = 872, the final R = 0.0350 and wR = 0.1226. The complex is an A…D…D＇…A＇ H-bonded tetramer. The intermolecular N-H…O and N-H…N hydrogen bonds, together with π-π stacking interactions, stabilize the crystal structure by forming a supramolecular architecture. It is found that, in solid state, the fluorescence emission of the complex is quenched significantly while the UV-vis spectrum exhibits a broad band at 346 nm with shoulder, which can be attributed to the donor-acceptor complex formed.
基金the National Natural Science Foundation of China(No.61178057)for financial support
文摘Three-photon absorption（3PA） of a push-pull chromophore,2-（3-cyano-（3-（4-（dimethylamino）styryl）-5,5-dimethylcyclohex- 2-enylidene）methyl）-5,5-dimethylfuran-2-ylidene） malononitrile（CFM） including TCF group was measured by the nonlinear transmission method using a femto-second Ti：Sapphire oscillator-amplifier laser system.Its three-photon absorption cross-sections at 1300 ran were 36.8×10^-79 cm^6 s^2 in the solution of DMF and 12.3×10^-79 cm^6 s^2 in the solution of CH_2Cl_2,respectively.The large values were got by experiments in this paper,which is a new exploration for these kinds of materials.The molecule has the potential application foreground of 3PA areas and optical power limiting.
基金Supported by the Natural Science Foundation of Southeast University under Grant No XJ0706271. We thank Professor Long Ba, Guohua Hu and Yuqiao Wang for help in the process of device preparation and measurements.
文摘ZnO is introduced as an alternative to TiO2 in dye sensitized solar cells （DSSCs） due to its band gap similar to TiO2, higher electron mobility, and flexible procedures of preparations. Several samples of ZnO films are prepared with the hydrothermal synthesis method and the sol-gel technique, respectively. These ZnO films were assembled as photoanodes in DSSCs using N3 dye as the sensitizer. The ZnO-based cells prepared by the hydrothermal synthesis show typical current source characteristics, whose fill factor （FF） is 0.44 and photo-to-electric power conversion efficiency is 0.34%. On the other hand, all the samples prepared with the sol-gel technique show accompanied source characteristics with relatively higher power conversion efficiencies （1%） but a lower FF （0.26）. X-ray diffraction （XRD） and atomic force microscopy （AFM） measurements indicate that the sol-gel samples have small particles sizes. Therefore, sol-gel samples could adsorb more dye molecules to generate high conversion efficiencies. At the same time, more grain boundaries make it more possible for injected electrons to recombine with the oxidized electrolyte. Hydrothermal samples have bigger grains, so they show poor conversion efficiency and relatively high FF.
基金supported financially by National Natural Science Foundation of China(Nos.20774039,20872061)the National Basic Research(No.2007CB925103)
文摘A novel octupolar chromophore with 1,3,5-triazine as core,2,7-divinylene-9,9-dimethylfluorene as extendedπ-conjugated bridge,triarylamine as the electron-donating end-groups was successfully synthesized and characterized.Their linear photophysical and two-photon absorption（TPA） properties were investigated by UV absorption,excited fluorescence（SPEF） spectra and nonlinear transmission method,respectively.The absorption cut-off of the chromophore is below 520 nm and it has stronger fluorescence emission in a nonpolar solvent.In addition,the chromophore exhibits larger TPA cross-section（226.0 GM） in the femtosecond regime at 800 nm.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60877024, 10374013, 60576008, 1067402 and 60725413, the National High-Tech Research and Development Programme of China under Grant No 2006AA03Z313, the National Basic Research Programme of China under Grant No 2007CB936300, and the Natural Science Foundation of Jiangsu Province （BK2006553）.
文摘Strong second-order nonlinear effect of ZnO nanowires on a silicon wafer are demonstrated by using the hyper- Rayleigh scattering （FIRS） measurement. The large nonlinear effect can be attributed to the following two factors： （1） the large total dipole moment caused by high surface defect density and electrostatic potential gradient, （2） coherent effect due to high crystal quality of single nanowire. Moreover, the second-order nonlinear effect is found to become weaker when the chip is put into organic solvent due to modification of surface defect caused by organic molecules. The variation of second-order signal in the solvent indicated the potential applications of ZnO nanowires as a sensor-on-chip （SoC）.
文摘We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes.
文摘An organic dye salt trans-4-[p-（N-hydroxyethyl-N-methylamino）styryl]-N-methylpyridinium iodide （ASPI） is doped with an electron transport organic molecule tris（8-hydroxyquinoline） aluminium （Alq3） in a host matrix of poly（methylmethacrylate） （PMMA）, and the amplified spontaneous emission （ASE） is studied. By efficient Forster energy transfer from Alq3 to ASPI, it is demonstrated that the ASE threshold of ASPI：Alq3：PMMA waveguide （about 11 μJ/pulse） is much lower than that of ASPI：PMMA system （about 38 μJ/pulse）. Meanwhile, the peak position of ASE can be controlled by the effect of film thickness on waveguide modes. We show that the ASE peak position can be tuned over 37nm. These characteristics indicate the ASPI：Alq3 system as a promising gain medium for optical amplifiers and organic semiconductor lasers.
