掺铒碲钨酸盐玻璃及其平面波导

研制了一种用于宽带波导放大器的掺铒碲钨酸盐激光玻璃材料，对玻璃热稳定性、光谱性质进行了表征，并在其上采用离子交换法制作了平面光波导．掺铒碲钨酸盐玻璃的转变温度Tg和析品开始温度Tx分别为377．1和488．5℃；荧光半高宽为52nm；应用McCumber理论，计算得出Er^3+离子4I13／2→^4I15／2跃迁在峰值波长1532nm的受激发射截面为0．91×10^-20cm^2．不同条件下制作了在632．8nm处多模的平面光波导，通过拟合得到Ag^+离子在300℃的有效扩散系数De为2．82×10^-1

钕离子掺杂和钕铝共掺高硅氧玻璃的光谱性质研究

Nd-doped and Nd-Al-codoped high silica glasses were obtained by sintering porous glass impregnated with Nd3+ and Al3+ ions. The absorption, fluorescence spectra and fluorescence lifetime of Nd-doped and Nd-Al-codoped high silica glasses were measured. The intensity parameters Omega(1), ( t = 2, 4, 6), fluorescence lifetime, radiative quantum efficiency and stimulated emission cross section were calculated by Judd-Ofelt theory. The effect of aluminum codoping on the fluorescence and structural properties of Nd-doped silica glass has been discussed. By comparing the spectroscopic properties with other Nd-doped oxide glasses and commercial silicate glasses, this Nd-doped high silica glass is likely to be a promising laser material for use in high power and high repetition rate lasers.

铕离子掺杂和铕铝共掺高硅氧玻璃的光谱性能

Eu-doped and Eu/Al-codoped high silica glass to investigate the properties of europium ions in high silica glasses were obtained. The porous glasses were immersed into europium nitrate solution or mixed solution of europium nitrate and aluminum nitrate. After dried, the doped porous glasses were sintered at 1200°C to obtain Eu-doped and Eu/Al-codoped high silica glasses. The reduction of Eu³⁺&rarrEu²⁺ was observed in Eu/Al-codoped high silica glass. The ratio of trivalent and bivalent europium ions was adjusted by the addition of aluminum ions and then the luminescent color of the glasses was controlled. A detailed mechanism was given to explain this reduction process.

碱金属氟化物对掺Yb~(3+)氟磷酸盐玻璃析晶稳定性和光谱性质的影响

研究了碱金属氟化物对掺Yb3+氟磷玻璃的光谱性质和析晶稳定性能的影响。运用倒易法计算了Yb3+的发射截面。结果显示,LiF的引入对吸收和发射截面的提高作用较大并出现最佳引入量极值,其次为KF。碱金属氟化物的引入可提高二元体系的析晶稳定性能,使玻璃网络结构得到改善;拉曼光谱显示二元体系中引入YbF3后玻璃网络结构得到增强,而在引入碱金属氟化物的三元体系中掺杂YbF3后破坏了网络完整性,降低系统析晶稳定性能。

Special effects of YbF3 on the structural changes for fluorophosphate glass

From Raman and IR spectra, obvious differences of the glass structure were observed in non-Yb3+-doped and Yb3+ -doped fluorophosphate glasses. Results showed that Yb3+ ions can induce, in a better glass, polymerization and network uniformity. Compared with the monophosphate-mastered Yb3+-free glass, Yb3+-doped glass has a pyrophosphate environment. The main building blocks in Yb3+ -doped samples are metaphosphate groups, pyrophosphate groups (P-2(O,F)(7),PO3F), Al[F-6]+Al[O,F](6) and F3Al-O-AlF3 while those of the Yb3+ -free glasses are monophosphate groups P(O,F)(4), little pyrophosphate groups, Al[F-4]+Al[F-6]+Al[O,F](4)+Al[O,F](6) and F3Al-O-AlF3. The DSC analysis also showed a slight increase in crystallization stability. (c) 2005 Elsevier B.V. All rights reserved.

掺铒磷酸盐玻璃波导放大器的特性研究

研究了掺铒磷酸盐玻璃波导放大器的特性。利用重叠因子将980nm光抽运的掺铒玻璃波导放大器四能级模型的速率-传输方程进行化简，在考虑上转换效应和放大自发发射的情况下．利用数值模拟的方法，得到了掺铒玻璃波导放大器的增益与Er^3+离子浓度、抽运功率、波导长度等参量之间的关系曲线；同时模拟出放大自发发射曲线并与实验测量结果进行比较。结果表明在考虑上转换效应和放大自发发射的情况下,理论结果和实验测量结果是一致的。同时看到，选择合适的铒离子浓度是制作掺铒玻璃波导放大器的关键；并且为了全面发挥掺铒玻璃波导放大器的性能

用于波导放大器的Er^3＋／Yb^3＋共掺磷酸盐玻璃的性能研究

通过优化熔融条件和玻璃组份，成功开发出一种新的Er^3+／Yb^3+共掺磷酸盐玻璃，其在沸水和熔盐中均表现出很好的化学稳定性。通过分析室温下Er^3+／Yb^3+共掺磷酸盐玻璃的吸收光谱，计算得到了Er^3+离子在波长1533nm处的峰值发射截面和杜得-奥菲而特强度参数；其中Er^3+离子在波长1533nm处的峰值发射截面为0．72×10^20cm^2，大于Schott的IOG1玻璃中Er^3+离子的峰值发射截面0．67×10^-20cm^2。通过改变离子交换的条件，获得了1．55μm单模光波导的制作条件

Er^3＋掺杂钨酸铅晶体的发光和光谱特征

本试验测试了Er^3＋掺杂钨酸铅晶体（PbWO4：Er^3＋）的吸收光谱，依据J-O理论，首次计算报道了光谱项特征：J-O强度参数、量子荧光效率、荧光分支比等，Ω2=3．75×10^-20cm^2，Ω4=0．67×10^-20cm^2，Ω6=0．41×10^-20cm^2。计算证实，PWO：Er^3＋中几乎有80％的激发能量非辐射跃迁转移致^4I13／2能级，^4I13／2的计算寿命是5200μs，J-O计算显示，在PWO中产生^4I13/2→^4I15/2和发射1．53μm．有高的几率。讨论了不同浓度E

Growth and spectral properties of Er:Gd2SiO5 crystal

Er3+ -doped Gd2SiO5 (Er:GSO) single crystal with dimensions of circle divide 35 x 40 mm(3) has been grown by the Czochralski method. The absorption and fluorescence spectra of the Er:GSO crystal were measured at room temperature. The spectral parameters were calculated based on Judd-Ofelt theory, and the intensity parameters Omega(2), Omega(4) and Omega 6 are obtained to be 6.168 x 10(-20), 1.878 x 10(-20), and 1.255 x 10(-20) cm(2), respectively. The emission cross-section has been calculated by Fuechtbauer-Ladenbury formula. (c) 2007 Elsevier B.V. All rights reserved.

Infrared emissions, visible up-conversion, thermoluminescence and defect centres in Er(3)Al(5)O(12) phosphor obtained by solution combustion reaction

The Er(3)Al(5)O(12) phosphor powders were prepared using the solution combustion method. Formation and homogeneity of the Er(3)Al(5)O(12) phosphor powders have been verified by X-ray diffraction and energy-dispersive X-ray analysis respectively. The frequency up-conversion from Er(3)Al(5)O(12) phosphor powder corresponding to the (2)H(9/2) -> (4)I(15/2), (2)H(11/2) -> (4)I(15/2), (4)S(3/2) -> (4)I(15/2), (4)F(9/2) -> (4)I(15/2) and the infrared emission (IR) due to the (4)I(13/2) -> (4)I(15/2) transitions lying at similar to 410, similar to 524, similar to 556, 645-680 nm and at similar to 1.53 mu m respectively upon excitation with a Ti-Sapphire pulsed/CW laser have been reported. The mechanism responsible for the frequency up-conversion and IR emission is discussed in detail. Defect centres induced by radiation were studied using the techniques of thermoluminescence and electron spin resonance. A single glow peak at 430A degrees C is observed and the thermoluminescence results show the presence of a defect center which decays at high temperature. Electron spin resonance studies indicate a center characterized by a g-factor equal to 2.0056 and it is observed that this center is not related to the thermoluminescence peak. A negligibly small concentration of cation and anion vacancies appears to be present in the phosphor in accordance with the earlier theoretical predictions.

Potentialities and practical limitations of absolute neutron dosimetry using thin films of uranium and thorium applied to the fission track dating

Neutron dosimetry using natural uranium and thorium thin films makes possible that mineral dating by the fission-track method can be accomplished, even when poor thermalized neutron facilities are employed. In this case, the contributions of the fissions of (235)U, (238)U and (232)Th induced by thermal, epithermal and fast neutrons to the population of tracks produced during irradiation are quantified through the combined use of natural uranium and thorium films.If the Th/U ratio of the sample is known, only one irradiation (where the sample and the films of uranium and thorium are present) is necessary to perform the dating. However, if that ratio is unknown, it can be determined through another irradiation where the mineral to be dated and both films are placed inside a cadmium box.Problems related with film manufacturing and calibration are discussed. Special attention is given to the utilization of thin films having very low uranium content. The problems faced suggest that it may be better to substitute these films by uranium doped standard glasses calibrated with thicker uranium films (thickness greater than 1.5 x 10(13) mu m).

Local Er(III) environment in luminescent titanosilicates prepared from microporous precursors

The local environment of Er3+ ions in microporous titanosilicate ETS-10 and in synthetic narsarsukite and glassy materials obtained by calcination of ETS-10 has been investigated by EXAFS, Raman and photoluminescence spectroscopies. Er L-III-edge EXAFS studies of Er3+-doped ETS-10 support the view that the exchanged Er3+ ions reside close to the (negatively charged) TiO6 octahedra. In ETS-10, Er3+ is partially bonded to framework oxygen atoms and hydration water molecules. The Er...Ti distance (3.3 Angstrom) is similar to the Na...Ti distances (3.15-3.20 Angstrom) reported previously for Na-ETS-10. Although the exact location of the ErO6 units within the host structure of Er3+-doped synthetic narsarsukite is still an open question, it is most likely that Er3+ substitutes Ti4+ rather than Na+ ions. EXAFS spectroscopy indicates that no significant clustering of erbium atoms occurs in the titanosilicate samples studied. Evidence for the insertion of Er3+ ions in the framework of narsarsukite has been obtained by Raman spectroscopy. This is indicated by the increasing full-width at half-maximum (FWHM) of the 775 cm(-1) peak and the increasing intensity of the anatase peaks as the erbium content increases. In addition, as the narsarsukite Er3+ content increases a band at ca. 515 cm(-1) firstly broadens and subsequently a new peak appears at ca. 507 cm(-1).Er3+-doped narsarsukite exhibits a characteristic local vibrational frequency, (h) over bar omega ca. 330 cm(-1), with an electron-phonon coupling, g ca. 0.2, which constitutes additional evidence for framework Er3+ insertion. The number of lines in the infrared emission spectrum of synthetic narsarsukite indicates the presence of two optically-active erbium centres with very similar local environments and an average I-4(13/2) lifetime of 7.8 +/- 0.2 ms.

Geração de segundo harmônico em vidros teluritos TeO2 – LiNbO3

Pós-graduação em Ciência dos Materiais - FEIS

Produção e caracterização de guias de onda dopados com terras-raras contendo nanopartículas semicondutoras.

O presente trabalho tem como objetivo estudar a produção e caracterização de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopartículas (NPs) semicondutoras, dopados e codopados com íons de Er3+ ou Er3+/Yb3+ para a produção de amplificadores ópticos. A produção de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia óptica seguida por processo de corrosão por plasma e deposição física a vapor. A incorporação dos íons de terras-raras (TRs) foi verificada a partir dos espectros de emissão. Análises de espectroscopia e microscopia foram indispensáveis para otimizar os parâmetros dos processos para a construção dos guias de onda. Foi observado aumento significativo da luminescência do Er3+ (região do visível e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presença de nanopartículas de Si. As perdas por propagação mínimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presença de NPs de silício (1,8 dB/cm). O ganho óptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de silício também foi medido. Ganho de ~8dB/cm em 1542 nm, sob excitação em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 átomos/cm3, Yb = 3,60.1020 átomos/cm3) com largura de 80 µm; para os guias codopados com concentração superior de Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) e com NPs de Si, foi observado aumento do ganho óptico de 50% para guia com largura de 100 µm. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, são promissores para aplicações em dispositivos fotônicos.