最新刊期
卷 12 ， 期 2 ， 1991
- 摘要：According to Sellmeier equation, the calculation and analysis on the collinear sum-frequence generation and frequency doubling in biaxial crystal LiB3O5(LBO) are made in terms of principle axes. The results demonstrate that sum-frequency mixing of a Nd:YAG laser<1.064nm)and a dry laser (from 0.56μm to 0.85μm) radiation can be realized in both of the two types of phase-matching(PM)process. Type Ⅱ PM is generally more efficient than that of type Ⅰ, while type Ⅰ is phase matchable over a larger wavelength range. As mentioned in the latter, 0.266μm UV radiation can be generated by sum-frequency mixing of the Nd:YAG laser with 1.064μm radiation and its third-harmonic generation with 0.355μm radiation by type I PM process in LBO crystal.An interesting feature of sum-frequency generation and frequency doubling in LBO is that non-critical phase matching(NCPM)can be obtained in x-y plane (type Ⅰ PM)and in y-z plane (type Ⅱ PM) at room temperature, while the nonlinear coefficient deff reaches its maximum. NCPM ensures the advantage of both a large acceptance angle and a small walkoff angle, thus makes LBO with a longer coherent length and higher efficiency in frequency conversion. The curves of the phase matching angle,effective nonlinear coefficient,walkoff angle, acceptance angle and spectral bandwidth versus the fundamental wavelength are plotted according to the formulas we derived in type I PM in x-y plane and type Ⅱ PM in y-z plane, respectively. The theoretical guiding to experiments and applications in LBO is presented.111|99|2更新时间：2020-08-11
- 摘要：The spontaneous and stimulated emission in Ⅱ-Ⅵ compounds such as CdS, CpSe and ZnSe have been studied [1-5]. In this paper, we report the first observation of spontaneous and stimulated emission at 77 K in VPE ZnSxSe1-x epilayers, which were grown on (100)GaAs substrate[6].The diagram of experimental setup is shown in Fig.1.Usually, there is only E band in the photoluminescence (PL) spectra in VPE ZnSxSe1-x epilayers excited with 337.1 nm line of a N2 laser at 77K, as shown in Fig.2. E band should be attributed to the free ex-citon recombination scattered by electrons[7].132|108|0更新时间：2020-08-11
- 摘要：The electronic structure and spectrum of laser crystal MgO:Ni2+ are investigated. The theoretical method used includes a DV-Xα method of calculating electronic structures and spectra of transition-metal com-plexs supposed[1]. It has taken account of the multiplet effects arising from the metal-ion 3d electrons by extending the one-electron DV-Xa calculation and incorporating with Bird's molecular orbital description of Ligand-field spectra.The one-electron energy levels, total density of states, spin polarization splitting and spin-orbital coupling constant are given. The charge transfer transition energy is calculated with the transition state theory. All the crystal-field transition energies are obtained by calculating the two-electron integrals based on results of the spin-restricted one-electron DV-Xα calculation. Results obtained are in good agreement with the experimental ones.114|117|0更新时间：2020-08-11
- 摘要：Design and fabrication of 1.3nm InGaAsP/InP DH LED with a monolithic integral lens, which exhibits high-speed performance,have been presented.Dependences of operating characteristics, such as the coupled power, the far field radiation patterns and the cut-off frequency on the LED and fiber structure parameters, have been analyzed and applied to complete an optimal design. LED's coupled to graded fiber with 50μm core, 0.2NA were fabricated at the wavelength of 1.3μm. A significant improvement has been achieved particularly in the cut-off frequency and the maximum value of 425MHz at 150mA has been realized.Remarkable improvement in the coupling efficiency is demonstrated.164|120|0更新时间：2020-08-11
- 摘要：Na5Eu(MoO4)4 like Na6Eu(MoO4)4 is a kind of good stoichiometric host luminescent material having high concentration of Eu3+ and no concentration quenching effect.The power crystals Na5Eu(MoO4)4 and NaEu(MoO4)2 have been synthesized. According to differential thermal and X-ray diffraction analyses, a phase diagram of the system Na2MoO4-Eu2(MoO4)3 has been determined.The methods for synthesizing pure Na5Eu(MoO4)4 and NaEu(MoO4)2 have been determined. It shows that Na5Eu(MoO4)4 will not be dissociated to NaEu(MoO4)2 when Na2MoO4 is excessive and the ratio of molal concentration of Na2MoO4 to Eu2O3 is more than about 8:1 at sintering temperature lower than 700℃.Both of Na5Eu(MoO4)4 and NaEu(MoO4)2 crystallize in the schee-lite structure type and belong to the tetragonal crystal system. The X-ray powder diffraction pattern of NaEu(MoO4)2 was indexed in a"pure" scheelite cell with parameters α=0.5236nm and c=1.1439nm (dcaic=5.24g/cm3, z=2, space group I41/α). Thus, the entire series of NaEu (MoO4)2 compounds is isostructural. But all of the X-ray powder diffraction lines of Na5Eu(MoO4)4 can only be indexed in the enlarged scheelite cell with parameters α=1.1439nm and c=1.1486nm (dcaic=4.01g/cm3, z=4, space group I41/α). In this paper, the cation distribution in the unit cell of both compounds is discussed.The purity of Na5Eu(MoO4)4 and NaEu(MoO4)2 samples can be determined sensitively by the intensity analysis of main peaks of the two compounds by X-ray diffraction mathod.The excitation and emission spectra of both compounds have been determined.115|134|4更新时间：2020-08-11
- 摘要：Since the discovery of high-Tc superconductivity in Bi-Sr-Ca-Cu-O system, a great deal of efforts has been made to study the structure and electronic properties of superconducting phases. The di cussion on Raman spectra of high-Tc superconductor aims to clarify the feature of phone structure and to gain information on physical properties of material. Much research work has been done on Raman spectra of Bi-Sr-Ca-Cu-O systeem while a little on Pb-doped Bi-Sr-Ca-Cu-O system.This paper discusses the similarities and differences of Raman spectra from (2212) single crystal (Tc=85K, sp1), Pb doped (2223) phase (Tc=107K, sp2) and Pb-doped Bi-Sr-Ca-Cu-O nonsuperconductor which is amorphous solid (sp3). The spectra involve in 20-720cm-1. Raman spectra were excited by an argon laser (λ=514.5nm) and detected by Model SPEX-140 Raman Spectrometer with a resolution of 4cm-1. AⅡ the experiments were carried out at room temperature.The lines of 169, 456-466 and 631-650cm-1 only occur in the spectra of sp1 and sp2. The spectrum of sp3 is quite different from those of sp1 and sp2 either in the location of lines or the structure of spectrum, which suggests the structure disparity. The most unambiguous character is that high intensity lines are always narrow, and they pile up on two broad weak backgrounds.116|132|0更新时间：2020-08-11
- 摘要：The bistable bahavior originating from optical nonlinear coupling between a prism and a nonlinear waveguide by using Fresnel formulas is described. Modulation and feedback curves of the optical bistable device are analyzed. Optical bistable curves at different offset angles are calculated.The results show that the smallest offset angle and threshold of the device can be determined by using this method.In prism nonlinear waveguide coupling system, as shown in Fig. 2, assuming prism the index of refraction n0=1,751, gap(air) s=100nm and its index of refraction n1=1.000, waveguide thickness w=1400nm and its index of refraction n2=n20+n2EIg=1.527 +10-14m2/W, substrate index of refraction offset angles (values of the angle shift from the incidence coupling angle) are calculated. If the offset angle △θ<0.18', optical switch occurs. If the offset angle △θ>0.18', optical bistable operation occurs. And the hysteresis cycle width and threshlod power increase with the increase of offset angle.126|134|0更新时间：2020-08-11
- 摘要：In this report, the refractive index-profile of semiconductor-doped glass waveguide has been determined based on the measurement of effective refractive indices of the multi-mode waveguide. Firstly, a reiterative method is used to determine the surface refractive index of waveguide with the effective refractive index measured. And then the different order mode depth and the effective refractive-indices of waveguide are evaluated by computer with the Fermi refractive index-profile mode equation. When laser power density coupled into the waveguide is changed, the nonlinear refractive index coefficient of the waveguide can be measured in different mode depth. So the nonlinear refractive index coefficient versus power densities is obtained and the nonlinear saturation value is 1.54×10-4.127|167|0更新时间：2020-08-11
- 摘要：The synthesis of 4 (SrEu)O·7Al2O3 phosphor and the effects of the concentration of activator Eu, contents of B2O3 and P2O5 on fluorescence property were investigated.The phosphors were prepared by solid state reaction of Al(OH)3, SrCO3, Eu2O3 and H3BO3, firing in air at 1550℃ for 3hr followed by flowing in H2-N2 at 1250℃ for 3hr.It was found that B2O3 and P2O5 influenced the luminescence brightness and emission spectra of the phosphor. The emission peak of phosphor shifted from 520nm to 490nm with adding H3BO3 and (NH4)2 HPO4 in raw material. Meanwhile, the emission intensity was remarkably enhanced by adding (NH4)ZHPO4 to starting material.The results show that adding P2O5 to 4(Sr1-xEux)0.7Al2O3 leads to more effective energy transfer from 410 emititng center to 490nm one. The two bands might be originated from inequivalent Eu ions (Eu ions on different crystallographic sites)In addition to the fast decay of phosphor (τ~40-50μs), the long fluorescence aftergrow was also observed to last for a few hours.241|528|30更新时间：2020-08-11
- 摘要：Luminescence properties of the salicylic-RE complex have been studied. The results for salicylic-RE complex doped with Tb3+ or Tb3+/Gd3+ ions show that they are high efficiency luminescent materials. The energy transfer between salicylic radical and Tb3+ ions were observed through the measurement of excitation spectrum and emission spectrum as well as fluorescence decay time and it was quite efficient from salicylic radical to Tb3+ or Tb3+/Gd3+. The substitution of 4/5 mol Tb3+ for Gd3+ ions was obtained with satisfatory results.The following formula can be used to estimate the energy transmission efficiency between salicylic radical and Tb3+ ions: P=1/τ*-1/τ (1) η=1-τ*/τ (2) where P is energy transmission probability, η the energy transmission efficiency,and τ and τ* are decay time of sal and sal-Tb3+ respectively.124|123|13更新时间：2020-08-11
- 摘要：The pure, 0.005, 0.01, 0.2 and 0.5 wt% Cr2O3-doped strontium titanate single crystals were prepared using melt method in a reduction atmosphere (N2). The transmission spectra at room temperature and the fluorescence spectra above 6.5 K were measured under various annealing conditions for thess crystals. The oxidization-heating-induced absorption and the effects of annealing and concentration on the luminescence from the crystals were studied in detail.The pure as-grown SrTiO3 crystal is dark in colour because of the absorption of oxygen vacancy, and no fluorescence occurs from it. After annealing in air atmosphere, most of oxygen vacancies are removed from the crystal and it turns a yellow colour. The yellow sample has a weak sharp line emission near 794 nm which is attributed to the ppm Cr in the crystal.The lightly doped as-grown SrTiO3 crystals (0.005 and 0.01 wt%) have three colours: yellow, dark green and dark, in which the yellow sample has an intense emission in near infrared region consisting of sharp line at 794 nm and its sidebands and being ascribed to the vibronic transition 2E-4A2 of Cr3+ ion. The dark green and dark ones have no fluorescence to be seen at any temperature, and after annealing in air atmosphere above 660℃ they can turn yellow or red (dark red) colour determined by whether the time of annealing is short or long and the temperature of annealing is low or high. The red sample has a weaker fluorescence than the yellow one. It is mainly due to the oxidization from Gr3+ to Cr4+ ion. The oxidization-heating-induced absorption peak appears near 530 nm and is attributed to the absorption of Gr4+ ions in the crystal.The heavily doped as-grown samples (0.2 and 0.5 wt%) have dark red and dark colours and after annealing above 660℃ they turn dark. The dark red samples have a different emission from the lightly doped samples in which the sharp line emission of Gr3+ ion is much weakened and a new emission spectrum occurs in the longer wavelength region which is attributed to the Gr3+ -pair emission. No fluorescence occurs from the dark samples, which is mainly due to the intense absorption of Gr4+ ions.147|162|0更新时间：2020-08-11
- 摘要：With the development of the science and technique of solid, properties of the polaron in crystals have been of considerable interest. A lot of scholars studied the problem of the polaron by a variety of theoretical method, but many of them mainly concentrated their attention on the weak and intermediate coupling cases. In early 1970's, Huybrechts proposed a linear-combination-operator method, by which a strong-coupling polaron was discussed.107|145|4更新时间：2020-08-11
- 摘要：The use of laser excitation in the study of the absorption of two photons for chla was reported by Terenin (1968) and Liu Yixian (1981). This paper reports the fluorescence spectra of the higher excited singlet state for chla solution in n-pentane excited by xenon lamp (430nm),and the fluorescence excitation spectra.When centre emitting mode was applied to excited sample of chla solution (see Fig. la) the fluorescence of chla solution in the concentration range of 10-4-10-3 M at 300K excited by 430nm shows emission bands at about 665nm and 720nm, and in the concentration range of 10-7-10-5M, it shows emission band at about 493nm. The intensity rate of 665nm to 493nm is about 100(see Fig.2).However, when surface emitting mode was applied to excited sample of chla (see Fig.1b), the fluorescence of chla solution in the concentration range of 10-7-10-5M at 300K excited by 430nm shows emission bands at 520nm and 580nm, and it shows emission band at about 665nm only in the higher concentration range of 10-5-10-3M (see Fig.3). When sample was frozen to 77K excited by 430nm, its fluorescence shows emission bands at about 520nm, 580nm, 665nm and 720nm (see Fig.4).Absorption spectra and excitation spectra of chla were measured. Excitation spectrum of the fluorescence at 665nm coincides with absorption spectrum for chla. Two principal absorption peaks are at about 430nm and 660nm(see Fige.5e).The excitation spectrum of the fluorescence at 493nm shows peaks at 354nm and 430nm(see Fig.5a),while excitation spectrum of the fluorescence at 520nm shows peak at 430nm (see Fig,5b) and excitation spectrum of the fluorescence at 580nm shows pea- ks at 430nm and 490nm (see Fig.5c). It can be seen from the experimental results that the reabsorption of chla solution was minimized due to the use of surface emitting mode. So that the fluorescence at 520nm and 580nm was measured from transition of the higher excited singlet state S2 to the ground state S0. And weaker fluorescence at 493nm from transition S2-S0 was measured by higher detection sensitivity. From the experimental results processes of electronic transition in chla can be shown by the schematic energy level diagram in Fig. 6.169|232|0更新时间：2020-08-11
- 摘要：Persistent hole was burnt at room temperature within the 40cm-1 inhomogeneous line of 7F0-5D2 transition of divalent samerium in Sro.,Ba0.5FC10.5Br0.5.The holewidth detected with excitation spectrum is 7cm-1, and the depth is about 15%,124|184|7更新时间：2020-08-11
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