Effect of water content in sol on optical properties of hybrid sol-gel derived TiO2/SiO2/ormosil film

Sol-gel derived TiO2/SiO2/ormosil hybrid planar waveguides have been deposited on soda-lime glass slides and silicon substrates, films were heat treated at 150 degreesC for 2 h or dried at room temperature. Different amounts of water were added to sols to study their impacts on microstructures and optical properties of films. The samples were characterized by m-line spectroscopy, Fourier transform infrared spectroscopy (FT-IR), UV/VIS/NIR spectrophotometer (UV-vis), atomic force microscopy (AFM), thermal analysis instrument and scattering-detection method. The refractive index was found to have the largest value at the molar ratio H2O/OR = 1 in sol (OR means -OCH3, -OC2H5 and -OC4H9 in the sol), whereas the thickest film appears at H2O/OR = 1/2. The rms surface roughness of all the films is lower than 1.1 nm, and increases with the increase of water content in sol. Higher water content leads to higher attenuation of film. (C) 2004 Elsevier B.V. All rights reserved.

Intense frequency upconversion fluorescence of Er3+/Yb3+-codoped novel potassium-barium-strontium-lead-bismuth glasses

Er3+/Yb3+-codoped potassium-barium-strontium-lead-bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Based on the results of energy transfer efficiency, the optimal Yb3+/Er3+ concentration ratio is found to be 5:1. Intense green and red emissions centered at 525, 546, and 657 run, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. (c) 2004 Elsevier B.V. All rights reserved.

Fluorescence lifetime increase by introduction of F- ions in ytterbium-doped TeO2-based glasses

this paper was retracted

Fabrication and amplified spontaneous emission spectrum of Er3+-doped tellurite glass fiber with D-shape cladding

Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A single-mode Er3+-doped tellurite glass fiber with D-shape cladding was fabricated in this work. The characterization of amplified spontaneous emission (ASE) from this newly fabricated Er3+-doped tellurite fibers are exhibited. When pumped at 980 nm, a very broad erbium ASE nearly 150 nm around 1.53 mum is observed. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of 2 mW from Er3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW. The broad 1.53 mum emission of Er3+ in tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers. (C) 2004 Elsevier B.V. All rights reserved.

Spectroscopic and fluorescence decay behaviors of Yb3+ -doped SiO2-PbO-Na2O-K2O glass

The spectroscopic and fluorescent decay behaviors of Yb3+-doped SiO2-PbO-Na2O-K2O glass is reported in this work. Yb2O3 contents of 1, 1.5 and 2mol% are added into the glass. Through the measurement of absorption and fluorescence spectra, and fluorescent decay rate at room temperature and at low temperature (18 K), it is found that the nonradiative decay rate of Yb3+ ions is mainly determined by the interaction between residual hydroxyl groups and Yb3+ ions. Concentration quenching effect can be omitted in this glass up to the Yb3+ ion concentration of 8.98 x 10(20)/cm(3). Multiphonon decay rate is also very small because of the large energy gap between F-2(5/2) and F-2(7/2) levels of Yb3+ ions. (c) 2004 Elsevier B.V. All rights reserved.

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.

Comparison of spectroscopic parameters of 15 at% Yb : YAlO3 and 15 at% Yb : Y3Al5O12

Yb: YAlO3 (YAP) (15 at %) and Yb: Y3Al5O12 (YAG)(15 at %) have been grown using the Czochralski method. Their absorption and fluorescence spectra were measured at room temperature and important spectroscopic parameters were calculated. Through the comparison of spectroscopic parameters of Yb:YAP and Yb: YAG, all results indicate that 15 at % Yb:YAP crystal is a potential candidate used for compact, efficient thin chip lasers when the laser output wavelength is 1012 or 103 8 nm. (C) 2004 Elsevier B.V. All rights reserved.

Simulation of growth process of thin film on non-planar substrate

In (2 + 1) dimension, growth process of thin film on non-planar substrate in Kuramoto-Sivashinsky model is studied with numerical simulation approach. 15 x 15 semi-ellipsoids arranged orderly on the surface of substrate are used to represent initial rough surface. The results show that at the initial stage of growth process, the surface morphology of thin film appears to be grid-structure, and the interface width constantly decreases with the growth time, then reaches minimum. However, the grid-structure becomes ambiguous, and granules of different sizes distribute evenly on the surface of thin film with the increase of growth time. Thereafter, the average size of granules and the interface width gradually increase, and the surface morphology of thin film presents fractal properties. The numerical results of height-height correlation functions of thin film verify the surface morphology of thin film to be fractal for a longer growth time. By fitting of the height-height correlation functions of thin film with different growth times, the growth process is described quantitatively. (c) 2004 Elsevier B.V. All rights reserved.

Laser conditioning and multi-shot laser damage accumulation effects of HfO2/SiO2 antireflective coatings

Laser conditioning effects of the HfO2/SiO2 antireflective (AR) coatings at 1064 nm and the accumulation effects of multishot laser radiation were investigated. The HfO2/SiO2 AR coatings were prepared by E-beam evaporation (EBE). The singleshot and multi-shot laser induced damage threshold was detected following ISO standard 11254-1.2, and the laser conditioning was conducted by three-step raster scanning method. It was found that the single-shot LIDT and multi-shot LIDT was almost the same. The damage mostly > 80% occurred in the first shot under multi-shot laser radiation, and after that the damage occurring probability plummeted to < 5%. There was no obvious enhancement of the laser damage resistance for both the single-shot and multi-shot laser radiation of the AR coatings after laser conditioning. A Nomarski microscope was employed to map the damage morphology, and it found that the damage behavior is defect-initiated for both unconditioned and conditioned samples. © 2004 Elsevier B.V. All rights reserved.

Laser conditioning of ZrO2 : Y2O3/SiO2 mirror coatings prepared by E-beam evaporation

Laser conditioning effects of the dielectric mirror coatings with different designs were investigated. Simple quarter-wave ZrO2:Y2O3/SiO2 mirrors and half-wave SiO2 over-coated ZrO2:Y2O3/SiO2 mirror coatings were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously. During the sub-threshold fluence raster scanning, the minor damage about defects size was found and the assumption of pre-damage mechanism, based on the functional damage concept, was put forward. The improvement of the laser induced damage threshold (LIDT) was attributed to the benign damage of the defects and the dependence on the coating design owed to the damage growth behavior of different coating designs. (C) 2004 Elsevier B.V. All rights reserved.

Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films

The effects of oxygen partial pressure on the structure and photoluminescence (PL) of ZnO films were studied. The films were prepared by direct current (DC) reactive magnetron sputtering with various oxygen concentrations at room temperature. With increasing oxygen ratio, the structure of films changes from zinc and zinc oxide phases, single-phase ZnO, to the (002) orientation, and the mechanical stresses exhibit from tensile stress to compressive stress. Films deposited at higher oxygen pressure show weaker emission intensities, which may result from the decrease of the oxygen vacancies and zinc interstitials in the film. This indicates that the emission in ZnO film originates from the oxygen vacancy and zinc interstitial-related defects. From optical transmittance spectra of ZnO films, the plasma edge shifts towards the shorter wavelength with the improvement of film stoichiometry. (C) 2004 Elsevier B.V. All rights reserved.

Efficiency improvement of organic light-emitting diodes using 8-hydroxy-quinolinato lithium as an electron injection layer

Organic light-emitting diodes (OLEDs) using tris-(8-hydroxy-quinolinato) aluminum (Alq(3)) as an emitter, 8-hydroxy-quinolinato lithium (Liq) as an electron injection layer, were prepared. Experimental results show that the efficiency of device with Liq is three times higher than that without Liq. The device using Liq as an injection layer is less sensitive in efficiency to the Liq thickness than that using LiF. In addition to the Alq3 based devices, Liq is also very effective as an electron injection layer for 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl based blue OLED and poly (2-methoxy,5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene) based orange polymer OLED. (c) 2004 Elsevier B.V. All rights reserved.

1987 ecosystem view of management research in the Myakka River: review of Phase I and Phase II reports

This memorandum has four parts. The first is a review and partial synthesis of Phase 1 and Phase 2 Reports by Dr. Ernest Estevez of the Mote Marine Laboratory to the Board of County Commissioners of Sarasota County, Florida. The review and synthesis emphasizes identification of the most important aspects of the structure of the Myakka system in terms of forcing functions, biological components, and major energy flows. In this context, the dominant primary producers, dominant fish species and food habits, and major environmental variables were of articular interest. A major focus of the review and synthesis was on the river zonations provided in the report and based on salinity and various biological indicators. The second part of this memorandum is a review of a draft report by Mote Marine Laboratory on evaluation of potential water quality impacts on the Myakka River from proposed activities in the watershed. This Memorandum's third part is a review of resource-management related ecosystem models in the context of possible future models of the Myakka River Ecosystem. The final part of this memorandum is proposed future work as an extension of the initial reports.