High-density holographic recording parameters under different wavelength of a two dyes-sensitized photopolymer

The high-density holographic recording parameters of a novel two dyes-sensitized photopolymer under different exposure wavelengths are studied. The results show that the maximum diffraction efficiency, exposure sensitivity, maximum refraction index modulation, dynamic range, and the exposure time constant increases with the increase of the exposure wavelength. The analysis indicates that the scattering has an important role in the forming of the holographic grating. (c) 2005 Elsevier GmbH. All rights reserved.

A new photopolymerizable holographic recording material based on acrylamide and N-hydroxymethyl acrylamide

A new polyvinylalcohol-based photopolymeric holographic recording material has been developed. The recording is obtained by the copolymerization of acrylamide and N-hydroxymethyl acrylamide. Diffraction efficiencies near 50% are obtained with energetic exposure of 80mJ/cm(2). N-hydroxymethyl acrylamide can improve the optical quality of the film. With the increase of the concentration of N-hydroxymethyl acrylamide, the flatness of the film increases, scattering reduces and the straight image is clearer with a small distortion. The postexposure effect on the grating is also studied. The diffraction efficiency of grating increases further during postexposure, gradient of monomer exists after exposure.

A humidity-resistant highly sensitive holographic photopolymerizable dry film

A new humidity-resistant highly sensitive acrylamide-based photopolymeric holographic recording material has been developed. The photopolymer is resistant to the humidity of environment. Diffraction efficiencies near 50% are obtained with exposure energy of 60 mJ/cm(2) in materials of 150 mu m. thickness. Diphenyl iodonium chloride is added to the material and can increase the exposure sensitivity by a factor of more than 4 (to about 28 mJ/cm(2)). An image has been successfully stored in the material with a small distortion. (C) 2005 Elsevier B.V. All rights reserved.

Efeito da superalimentação neonatal sobre a função adrenal e o desenvolvimento da microesteatose hepática em ratos adultos

O estado nutricional e hormonal em fases iniciais de desenvolvimento (gestação e lactação) está relacionado a alterações epigenéticas, que podem levar ao desenvolvimento de doenças. A obesidade infantil está relacionada com a ocorrência da obesidade na idade adulta, resistência à insulina e maior risco cardiometabólico. Em estudos experimentais, a superalimentação neonatal causa obesidade e aumenta o risco de doenças cardiovasculares. Estes animais apresentam obesidade visceral, hiperfagia, hiperleptinemia e hipertensão na idade adulta. Previamente, demonstramos que a hiperleptinemia neonatal causa hiperfunção da medula adrenal e microesteatose na idade adulta. No presente estudo avaliamos a função adrenal de ratos adultos obesos no modelo de superalimentação neonatal por redução do tamanho da ninhada e a sensibilidade as catecolaminas no tecido adiposo visceral (TAV) e no fígado. Ao nascimento todas as ninhadas tiveram seu número de filhotes ajustados para 10. Para induzir a superalimentação neonatal, o tamanho da ninhada foi reduzido de dez para três filhotes machos no terceiro dia de lactação até o desmame (SA), enquanto que o grupo controle permaneceu com 10 filhotes durante toda a lactação. Após o desmame, os ratos tiveram livre acesso à dieta padrão e água até 180 dias (1 animal de cada ninhada, n = 7). O TAV e as glândulas adrenais foram pesadas. As contrações hormonais séricas, o conteúdo hepático de glicogênio e triglicerídeos foram avaliados por kits comerciais. O conteúdo e a secreção de catecolaminas adrenais foram avaliados utilizando o método do trihidroxindol. O conteúdo dos hormônios eixo hipotálamo-hipófise-córtex adrenal, das enzimas da via de síntese das catecolaminas na glândula adrenal, ADRB2 no fígado e ADRB3 no TAV foram determinados por Western blotting ou imunohistoquímica. As diferenças foram consideradas significativas quando p <0,05. Aos 180 dias de vida, o grupo SA apresentou maior massa corporal (+15%), maior consumo alimentar (+15%) e maior adiposidade visceral (+79%). Os hormônios do eixo hipotálamo-hipófise-córtex-adrenal não foram alterados. O grupo SA apresentou maior expressão de tirosina hidroxilase e de DOPA descarboxilase (+31% e 90%, respectivamente); conteúdo de catecolaminas adrenais (absoluta: 35% e relativa: 40%), e secreção de catecolaminas, tanto basal quanto estimulada por cafeína (+35% e 43%, respectivamente). O conteúdo ADRB3 no TAV não foi alterado nos grupo SA, entretanto o ADRB2 no fígado apresentou-se menor (-45%). O grupo SA apresentou maior conteúdo de glicogênio e triglicerídeos no fígado (+79% e +49%, respectivamente), além de microesteatose. A superalimentação neonatal resulta em hiperativação adrenomedular e aparentemente está associada a preservação da sensibilidade às catecolaminas no VAT. Adicionalmente sugerimos que o maior conteúdo de glicogênio e triglicerídeos hepático seja devido a menor sensibilidade as catecolaminas. Tal perfil pode contribuir para a disfunção metabólica hepática e hipertensão arterial que são características deste modelo de obesidade programada.

Low loss waveguide in Nd3+-doped silicate glass fabricated by carbon ion implantation

Low loss index enhanced planar waveguides in Nd3+-doped silicate glass were fabricated by 3.0 MeV C+ ion implantation. The enhancement of the refractive index confined the light propagating in the waveguide. The prism-coupling method was used to measure dark modes in the waveguide. The effective refractive indices of the waveguide were obtained based on the dark modes. The moving fiber method was applied to measure the waveguide propagation loss. Loss measured in non-annealed samples is about 0.6 dB/cm. And the waveguide mode optical near-field output at 633 nm was presented. (c) 2005 Elsevier B.V. All rights reserved.

Property studies of optical waveguide formed by 6.0 MeV carbon ion implantation into Nd : silicate glass

Nd:silicate glass was implanted at room temperature by 6.0 MeV C3+ ions with a dose of 2.0 x 10(15) ions cm(-2). A waveguide with thickness of about 6.3 mu m was formed. The prism-coupling method was used to observe the dark modes of the waveguide at 633 nm and 1539 nm, respectively. There are three dark modes at 633 nm, of which one is the enhanced-index mode. The propagation loss of the enhanced-index mode in the waveguide measured at 633 nm is 0.42 dB cm(-1) after annealing at 217 degrees C for 35 min. The reflectivity calculation method was applied to simulate the refractive index profiles in the waveguide. The mode optical near-field output at 633 nm was presented.

Effects of surface treatment on sapphire substrates

The influence of mechanical polishing, chemo-mechanical polishing (CMP), as well as CMP and subsequent chemical etching on the properties of sapphire substrate surfaces has been studied. The sapphire substrates have been investigated by means of polarizing microscopy, atomic force microscopy (AFM). X-ray diffraction rocking curves (XRCs) and micro-Raman spectroscopy. The results show that CMP with subsequent chemically etching yields the best-quality sapphire substrate surfaces. (C) 2004 Elsevier B.V. All rights reserved.

MOCVD growth and properties of ZnO thin films on LiNbO3 substrates

ZnO thin films were grown on (0001)LiNbO3 substrates by the MOCVD technique. The substrate temperatures during growth were changed from 400 to 600 degrees C. The X-ray diffraction (XRD) pattern of the ZnO film showed a strong [002] reflection peak, and the peak intensity was dependent on substrate temperature. The ZnO columnar grains were highly oriented along the (002) direction when the film processing temperature was 600 degrees C. The optical transmission and PL results also indicated that highest crystalline quality of the ZnO films could be obtained at elevated temperatures. (c) 2005 Elsevier B.V. All rights reserved.

Annealing effect on properties of ZnO thin films grown on LiNbO3 substrates by MOCVD

ZnO films were grown on (0 0 0 1) LiNbO3 substrates by metal organic chemical vapor deposition (MOCVD). Annealing of ZnO films was performed in air for I h at 800 degrees C. The effects of annealing on the structural and optical properties of ZnO thin films on LiNbO3 substrates were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) measurements. XRD patterns and AFM showed that the as-grown and the annealed ZnO films grown on LiNbO3 substrates had c-axis preferential orientation, the crystallinity of the ZnO films grown on LiNbO3 Substrates was improved, and the grain size increased by annealing. The PL spectra showed that the intensity of the UV near-band-edge peak was increased after annealing, while the intensity of visible peak (deep-level emission) decreased. (c) 2005 Elsevier B.V. All rights reserved.

Blue-yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique

We report on the realization of ZnO homojunction light-emitting diodes (LEDs) fabricated by metalorganic chemical vapor deposition on (0001) ZnO bulk substrate. The p-type ZnO epilayer was formed by nitrogen incorporation using N2O gas as oxidizing and doping sources. Distinct electroluminescence (EL) emissions in the blue and yellow regions were observed at room temperature by the naked eye under forward bias. The EL peak energy coincided with the photoluminescence peak energy of the ZnO epilayer, suggesting that the EL emissions emerge from the ZnO epilayer. In addition, the current-voltage and light output-voltage characteristics of ZnO homojunction LEDs have also been studied. (c) 2006 American Institute of Physics.

Structural, optical and electrical properties of ZnO films grown on c-plane sapphire and (100)gamma-LiAlO2 by pulse laser deposition

ZnO thin films were grown on single-crystal gamma-LiAlO2 (LAO) and sapphire (0001) substrate by pulsed laser deposition (PLD). The structural, optical and electrical properties of ZnO films were investigated. The results show that LAO is more suitable for fabricating ZnO films than sapphire substrate and the highest-quality ZnO film was attained on LAO at the substrate temperature of 550 degrees C. However, when the substrate temperature rises to 700 degrees C, lithium would diffuse from the substrate (LAO) into ZnO film which makes ZnO film on LAO becomes polycrystalline without preferred orientation, the stress in ZnO film increases dominantly and the resistivity of the film decreases exponentially. (c) 2005 Elsevier B.V. All rights reserved.

Spectral hole-burning of Eu3+: Y2SiO5 crystal at 579.62 mm

By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth : 0.5 cm(-1)) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu3+ : Y2SiO5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in (5)Do-(7)Fo transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength : 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.