246 resultados para LPS : Ce
Resumo:
We have investigated ultraviolet (UV) photorefractive effect of lithium niobate doubly doped with Ce and Cu. It is found the diffraction efficiency shows oscillating behavior Under UV-1ight-recording. A model in which electrons and holes can be excited from impurity centers in the UV region is proposed to study the oscillatory behavior of the diffraction efficiency. Oil the basis of the material equations and the coupled-wave equations, we found that the oscillatory behavior is due to the oscillation of the relative spatial phase shift Phi. And the electron-hole competition may cause the oscillation of the relative spatial phase shift. A switch point from electron grating to hole grating is chosen to realize nonvolatile readout by a red light with high sensitivity (0.4 cm/J). (c) 2005 Elsevier GmbH. All rights reserved.
Resumo:
Three wavelengths of red, green and blue of recording beams are systemically tested for the UV-assistant recording and optical fixing of holograms in a strongly oxidized Ce:Cu:LiNbO3 crystal. Three different photorefractive phenomena are observed. It is shown that the green beams will optimally generate a critical strong nonvolatile hologram with quick sensitivity and the optimal switching technique could be jointly used to obtain a nearly 100% high diffraction. Theoretical verification is given, and a prescription on the doping densities and on the oxidation/reduction states of the material to match a defined recording wavelength for high diffraction is suggested.
Resumo:
YAlO3 single crystal doped with Ce3+ at concentration 1% was grown by the temperature gradient technique. The as-grown crystal was pink. After H-2 annealing or air annealing at 1400degreesC for 20 h, the crystal was turned into colorless. We concluded there were two kinds of color centers in the as-grown crystal. One is F+ center attributed to absorption band peaking at about 530 nm, the other is O- center attributed to absorption band peaking at about 390 nm. This color centers model can be applied in explaining the experiment phenomena including the color changes, the absorption spectra changes, and the light yield changes of Ce:YAP crystals before and after annealing. (C) 2004 American Institute of Physics.
Resumo:
采用中频感应提拉法生长出尺寸为Ф60mm×110mm的Ce:Lu1.6Y0.4SiO5(LYSO)晶体,与LSO晶体相比,LYSO晶体的优势是提高了晶体质量、降低了熔点和原料成本等.在室温下测试了LYSO晶体的透过光谱、激发光谱和发射光谱,结果表明Y的加入使LSO晶体的吸收边向短波方向偏移.Ce^3+的4f^1→5d^1跃迁吸收导致紫外区产生三个吸收带.发射光谱具有Ce^3+典型的双峰特征,经Gaussian多峰值拟合,双峰395nm和418nm归属于Ce1发光中心,而435nm的发光峰与Ce2发光中心有
Resumo:
Photoluminescence spectrum of Ce:YAG single crystal was studied employing vacuum ultraviolet (VUV) synchrotron radiation. Intrinsic absorption edge at about 52,000 cm(-1) was observed in the absorption spectrum. From the VUV excitation spectrum, the energy of the highest d-component of 53,191 cm(-1) (188 nm) for the Ce3+ ions in YAG was obtained at 300 K. The disappearance of the third 5d level at 37,735 cm(-1) (265 nm) in absorption and excitation spectra in our samples may be due to the impurity Fe3+ ions absorption. (C) 2006 Elsevier Ltd. All rights reserved.
Resumo:
采用提拉法成功生长了纯LaAlO3和掺铈的LaAlO3单晶体,测试了它们的远红外吸收谱,紫外吸收谱,荧光谱,根据吸收光谱确定了晶体中Ce^3+的能级结构,利用这一能级结构模型较好地解释了Ce:LaAlO3晶体的荧光光谱。
Resumo:
Five absorption hands, at 227, 300 340, 370 and 457nm, were observed in the optical absorption spectrum of Ce:Y3Al5O12 (Ce:YAG) crystals grown by the temperature gradient technique (TGT). The absorption bands at 227, 340, and 457 nm were identified Lis belonging to the Ce3+ -ion in the YAG crystal. A near UV optical emission band at 398nm was observed. with an excitation spectrum containing two bands, at 235 and 370nm. No fluorescence was detected under 300 nm excitation. The pair of absorption bands at 235 and 370 nm and the absorption band at 300 nm were attributed to the F- and F+-type color centers, respectively. The color centers model was also applied to explain the spectral changes in the Ce:YAG (TGT) crystal, including the reduction in the Ce 31 -ion absorption intensity, after annealing in an oxidizing atmosphere (air). (C) 2004 Elsevier B.V. All rights reserved.
Resumo:
Color centers and impurity defects of Ce:YAG crystals grown in reduction atmosphere by temperature gradient techniques have been investigated by means of gamma irradiation and thermal treatments. Four absorption bands associated with color centers or impurity defects at 235, 255, 294 and 370 nm were observed in as-grown crystals. Changes in optical intensity of the 235 and 370 nm bands after gamma irradiation indicate that they are associated with F+-type color center. Charge state change processes of Fe3+ impurity and Ce3+ ions take place in the irradiation process. The variations of Ce3+ ions concentration clearly indicate that Ce4+ ions exist in Ce:YAG crystals and gamma irradiations could increase the concentration of Ce3+ ions. Annealing treatments and the changes in optical density suggest that a heterovalent impurity ion associated with the 294 nm band seems to be present in the crystals. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
Cerium-doped lutetium pyrosilicate crystal, Ce:Lu2Si2O7 (Ce:LPS), was grown by the Czochralski method. The segregation coefficient of Ce3+ ion was studied by the ICP-AES method. X-ray diffraction analysis showed that the structure of Ce:LPS crystal was monoclinic symmetry with space group of C2/m. Perfect cleavage planes (110) and imperfect cleavage planes (001) were observed by optical microscope. The reasons why it is difficult to grow crack-free crystals were studied. After optimized growth parameters, a Ce:LPS crystal with dimension of Phi 25 x 30 mm was grown, which is colorless, high optical quality, cracking-free and no inclusions. The transmittance of Ce:LPS crystal from 380 to 800 nm is over 82% and there is no observable absorption. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
用波长为266nm的激光激发不同尺寸、不同掺Ce^3+浓度的YAP:Ce闪烁晶体,测量其光致激光荧光衰减常数,测量结果表明:YAP:Ce闪烁晶体的光致荧光衰减常数约为18.2ns,且与实验晶体厚度及Ce^3+掺杂浓度(0.1%~0.6%原子分数)无关。
Resumo:
For the first time, a high optical quality Yb3+-doped lutetium pyrosilicate laser crystal Lu2Si2O7 (LPS) was grown by the Czochralski (Cz) method. The segregation coefficient of ytterbium ion in Yb:LPS crystal detected by the inductively coupled plasma atomic emission spectrometer (TCP-AES) method is equal to 0.847. X-ray powder diffraction result confirms the C2/m phase monoclinic space group of the grown crystal and the peaks corresponding to different phases were indexed. The absorption and fluorescence spectra, as well as fluorescence decay lifetime of Yb3+ ion in LPS have been investigated. The absorption and fluorescence cross-sections of the transitions F-2(7/2) <-> F-2(5/2) of Yb3+ ion in LPS crystal have been determined. The advantages of the Yb:LPS crystal including high crystal quality, quasi-four-level laser operating scheme, high absorption cross-sections (1.33 x 10(-2) cm(2)) and particularly broad emission bandwidth (similar to 62 nm) indicated that the Yb:LPS crystal seemed to be a promising candidate used as compact, efficient thin chip lasers when LD is pumped at 940 and 980 nm due to its low-symmetry monoclinic structure and single crystallographic site. (c) 2007 Elsevier B.V. All rights reserved.
Resumo:
Spectroscopic properties of Ce-doped yttrium orthoaluminate (Ce:YAlO3 or Ce:YAP) crystals grown by temperature gradient technique (TGT) were investigated, and the effects of the growth conditions on the properties were analyzed.. Methods of optical absorption (OA), photoluminescence (PL), photoluminescence decay (PLD), X-ray excited luminescence (XL) and cathodeluminescence (CL) were used in these investigations. The results showed that the absorption band peak at 202, 394 and 532 nm originated from F and F+ color center induced by the weak reducing growth atmosphere, green emission band near 500 ran derived from Ce3+ -Ce3+ pairs and band at 650 similar to 850 run from some unintentional impurity in crystals.
Resumo:
Gamma-rays radiation effects on Ce:YAG crystals grown by Czochralski (Cz) and temperature gradient techniques (TGT) have been studied by means of optical absorption and luminescence spectra. Valence of Ce3+ ion changes during the gamma-ray irradiation process and this result indicates Ce4+ ion may exist in both Cz-Ce:YAG and TGT-Ce:YAG crystals. Thermally stimulated luminescence measurements reveal intense thermoluminescence peaks in gamma-irradiated Ce:YAG crystals and trap parameters were calculated by general-order kinetics expression. (C) 2006 Elsevier B.V. All rights reserved.