Spectroscopic properties and thermal stability of Er3+-doped tungsten-tellurite glass for waveguide amplifier application

Tungsten-tellurite glass with molar composition of 60TeO(2)-30WO(3)-10Na(2)O has been investigated for developing planar broadband waveguide amplifier application. Spectroscopic properties and thermal stability of Er3+-doped tungsten-tellurite glass have been discussed. The results show that the introduction Of WO3 increases significantly the glass transition temperature and the maximum phonon energy. Er3+-doped tungsten-tellurite glass exhibits high glass transition temperature (377 degrees C), large emission cross-section (0.91 x 10(-20) cm(2)) at 1532 nm and broad full width at half maximum (FWHM), which make it preferable for broadband Er3+-doped waveguide amplifier application. (c) 2005 Elsevier B.V. All rights reserved.

Thermal analysis of glasses in TeO2-BaF2-LaF3 systems

Divalent metal fluorides MF2 (M=Sr, Mg, Ca) in oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were synthesized. The densities, refractive indices and characteristic temperatures of synthesized glasses were measured. The influence of divalent metal fluorides MF2 (M=Sr, Mg, Ca) on the thermal stability of oxyfluoride tellurite glasses TeO2-BaF2-LaF3 were studied. Results show that the replacement of BaF2 by SrF2 and MgF2 can enhance the thermal stability against crystallization of the glass. A glass system with good thermal stability was produced, which could be a potential candidate for the host materials of the fiber devices.

Spectroscopic properties and thermal stability of Er3+/Yb3+-codoped fluorophosphate glasses

A comprehensive study on the thermal stability and spectroscopic properties of Er3+/Yb3+-codoped Al(PO3)(3)-based fluorophosphate glasses is reported of the 1.5μ m fibre amplifiers in this paper. From optical absorption spectra, the Judd-Ofelt parameters of Er3+ in the glasses and several important optical properties, such as the radiative transition probability, the branching ratio and the spontaneous emission probability, have been calculated by using Judd-Ofelt theory. The fluorophosphate glass exhibits broadband near-infrared emission at 1.53μ m with a full width at half-maximum over 63nm, and a large calculated stimulated-emission cross-section of 6.85 x 10(-21)cm(2).

Effect of alkali and alkaline earth fluoride introduction on thermal stability and structure of fluorophosphate glasses

The thermal stability and structure of RF-RF2-AIF(3)-Al(PO3)(3) fluorophosphate glasses were investigated. Analyses of infrared absorbance spectra and Raman spectra reveal that with increasing number of alkali and alkaline earth fluoride components, the sum of P-O-P bond and O-P-O bond increases and glass network is strengthened. Consequently, the inhibition to nucleation and crystallization processes is improved, which is proved by the increment of thermal stability factors AT and S determined by differential scanning calorimetry. In addition, it was found that LiF has poor ability to form glass in univalent alkali fluorides and MgF2 has comparative strong ability to form glass in bivalent alkaline earth fluorides. (c) 2006 Published by Elsevier B.V.

Effect of CdF2 addition on thermal stability and upconversion luminescence properties in Tm3+-Yb3+ codoped oxyfluoride silicate glasses

Tm3+-Yb3+ codoped oxyfluoride silicate glasses suitable for upconversion laser has been fabricated. In this paper, effect of CdF2 addition on thermal stability and upconversion luminescence properties in Tm3+-Yb3+ codoped oxyfluoride silicate glasses have been systematically investigated. The experimental results indicate that, with the substitution CdF2 for PbF2, the glass thermal stability increases and the UV cutoff edge moves to short-wave band slightly. With increasing CdF2 content, the blue and red upconversion luminescence intensity increases slightly at first, and then increases rapidly. While the near infrared (NIR) upconversion emission intensity increases notably at first and then increases slightly. However, the blue and NIR luminescence intensity are much stronger than that of red, indicating these oxyfluoride silicate glasses are more preferable for blue and NIR emissions than red emission. The possible upconversion mechanisms for the blue, red and NIR fluorescence are also estimated and evaluated. (c) 2006 Elsevier B.V. All rights reserved.

Effects of thermal treatment on broadband near-infrared emission from Bi-doped chalcohalide glasses

GeGaSKBr glass with Bi ions as emission centers were fabricated. An intense emission centered at around 1230 nm with the width of more than 175 nm was observed by 808 nm photo-excitation of the glass. Lower quenching rate and thermal treatment promote micro-crystallization process, thus strengthening the emission. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.

Study on the hydrolytic property and thermal stability of LiAlO2 substrate

The hydrolytic property and thermal stability of LiAlO2 (LAO), important factors for its application, were examined by AFM and X-ray rocking curve. We found that H2O may be deleterious for LAO surface polishing when the root mean square (RMS) value is less than 1 nm. However, when the RMS value is more than 1 nm it may be useful for LAO polishing. (100)-plane LAO substrates are annealed in the range of 850-900 degrees C in flux N-2, Slick AlN layer probably is produced on the substrate surface. M-plane GaN layer has grown on the substrate by metal-organic chemical vapor deposition (MOCVD) method. Theses results show that LiAlO2 crystal is a promising substrate of fabricating high-efficiency LEDs by MOCVD. (c) 2006 Elsevier B.V. All rights reserved.

Thermal, spectroscopic and laser properties of Yb3+Na+: CaF2 single crystals

The effects of Na+ doping level on the thermal conductivities, absorption and emission spectra, and fluorescence lifetimes of Yb3+ ,Na+ :CaF2 crystals were systematically studied. Sites structure, covalent force, and crystal field strength of Yb3+ :CaF2 crystals were markedly varied by codoping Na+ as charge compensator. The 2.0at% Yb3+ and 3.0at% Na+-codoped CaF2 crystal was demonstrated to operate in diode-pumped passively mode-locking scheme. Transform-limited 1 ps laser pulses were obtained, showing the crystal capable of producing ultra-short laser pulses. (c) 2006 Elsevier B.V. All rights reserved.

Influence of vapor transport equilibration on the crystal quality and thermal-expansion coefficients of gamma-LiAlO2

gamma-LiAlO2 (LAO) single crystal has been grown by the Czochralski method. However, its quality was deteriorated due to lithium volatilization during the crystal growth. The full width at half maximum value drops from 116.9 to 44.2 arc sec after the LAO slice was treated by vapor transport equilibration at 1000, 1100, and 1200 degrees C/48 h in sequence. The treated slice shows higher optical transmission than the as-grown one in the measured wavelength range of 190-1900 nm, meanwhile, its absorption edge exhibits a blueshift. According to Raman spectra, the treated slice has homogeneous quality at different depths from surface to 0.01 mm. The expansion coefficient of the treated slice for a axis drops from 17.2398x10(-6)/degrees C to 16.5240x10(-6)/degrees C, and that for c axis drops from 10.7664x10(-6)/degrees C to 10.0786x10(-6)/degrees C.

Thermal stress-induced birefringence in borate glass irradiated by femtosecond laser pulses

Thermal stress-induced birefringence in borate glass which has been irradiated by 800-nm femtosecond laser pulses is observed under cross-polarized light. Due to the high temperature and pressure formed in the focal volume, the material at the edge of the micro-modified region is compressed between the expanding region and the unheated one, then stress emerges. Raman spectroscopy is used to investigate the stress distribution in the micro-modified region and indicates the redistributions of density and refractive index by Raman peak shift. We suggest that this technique can develop waveguide polarizers and Fresnel zone plates in integrated optics.

Optimization of thermal environment during crystal growth of large-sized Nd : YAG by Temperature Gradient Technique

A finite-element model is employed to analysis the thermal environments in Temperature Gradient Technique (TGT) furnace during the growth of large-sized Nd:YAG crystal. The obtained results show that when the crucible is located at the lower position inside of the heater, a flatter solid-liquid interface is established, which makes it easier to obtain the core-free Nd:YAG crystal. Meanwhile, the lower crucible position can induce higher axial temperature gradient, which is beneficial to the release of latent heat. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ synthesis of ZrO2/ZrW2O8 composites with near-zero thermal expansion

In this paper, ZrO2 and WO3 were used as the raw materials to prepare ZrO2/ZrW2O8 composites by in situ reaction method and the thermal expansion property of the composites was studied. This novel method included a heating step up to 1473 K for 24 h, which combines the synthesizing and sintering of ZrW2O8. The result indicates that ZrO2/ZrW2O8 composite shows near-zero thermal expansion when the weight ratio of ZrO2 and WO3 is 2.5:1. Compared with composites prepared previously by non-reactive sintering of ZrO2 and ZrW2O8, the composites show higher relative density and lower porosity.

Thermal and electric conductivity of near-zero thermal expansion ZrW 2O8//ZrO2 composites

In this work, the microstructure, thermal and electric conductivity properties of near-zero thermal expansion ZrW2O8/ZrO2 and Al2O3 added ZrW2O8/ZrO2 composites were studied. Both the two composites exhibit very low thermal conductivity and the thermal conductivity decreases slightly as the temperature increases. The electric conductivity of the two composites increases with the increasing of the measurement temperature. The Al2O3 added ZrW2O8/ZrO2 composite has higher thermal and electric conductivity than ZrW2O8/ZrO2 composite. The most important factor which causes the difference of the thermal and electric conductivity of the composites is the porosity. (C) 2008 The Ceramic Society of Japan. All rights reserved.