Toward a structural model for the aluminum tellurite glass system

Neutron diffraction, 27Al MAS NMR, and 27Al Double Quantum MAS NMR results are presented and analyzed to determine the local environments of the cations in a series of aluminum tellurite glasses. Total scattering results show that, within a maximum Te–O distance of 2.36 Å, tellurium exhibits a mix of [TeO3E] and [TeO4E] environments (E = electron lone-pair), with a linear reduction in the average tellurium–oxygen coordination number as Al2O3 is added to the glass. This is accompanied by a linear decrease in the average aluminum–oxygen coordination number as [AlO4] units form at the expense of [AlO6] units, while the fraction of [AlO5] units remains roughly constant. A consideration of the bonding requirements of the five structural units in the glass, [TeO3E], [TeO4E], [AlO4], [AlO5], and [AlO6], has allowed a direct quantitative relationship between tellurium–oxygen and aluminum–oxygen coordination numbers to be derived for the first time, and this has been successfully extended to the boron tellurite system. Double Quantum 27Al MAS NMR indicates that, in contrast to previous reports, the shortest Al...Al separations are significantly smaller (∼3.2 Å) than expected for a uniform distribution and there is a preference for [AlO6]–[AlO6] and [AlO4]–[AlO4] corner sharing polyhedra. These associations support a new structural model which successfully applies the principle of charge balance to describe the interaction of tellurium and aluminum and identifies and explains the clustering of [AlOn] polyhedra in the glass and their preferred associations. [AlO6] and [TeO4E] units dominate the network in TeO2-rich glasses and [AlO4]− units form to stabilize the [TeO3E]+ units as alumina is added to the glass

Characteristic of femtosecond titanium sapphire oscillator

A mode locked Titanium sapphire Ti:Al2O3 oscillator energized by Diode pumped solid state laser at 532 nm was developed and characterized. The oscillator was aligned based on z-folder cavity. The stability of the output was monitor via the oscilloscope. The mode locked frequency was operated at 75 MHz. The power was detected by high-speed photodiode and digitized on a broadband powermeter. The pulse duration was directly measured via autocorellator. A beam profiler was utilized to record the dynamic expansion of the beam along the Rayleigh region. The average output power of the laser was found to be as 260 mW corresponding the input power of 4 W. The energy of the femtopulse is 3.57 nJ with pulse duration of 50 fs. The focused intensity is achieved almost 4×108W/cm2 with M2~2

Generation of mode-locked pulse in non self-starting Ti:sapphire laser

Generation of mode locked pulse from non-self starting Titanium Sapphire laser is reported. Initially the output power of the Ti:sapphire laser was detected at various cavity lengths. The result shown that the stability region was found in the range between 104 to 106 mm. However the mode locked signal was only realized within 100 micron a distance apart at the near boundary of the stability region. The distribution of the mode lock pulsed in the stable zone is operating in a normal Gaussian profile

Comparative spectroscopic studies on luminescence performance of Er3+ doped tellurite glass embedded with different nanoparticles (Ag Co and Fe) at 0.55 µm emission

The spectroscopic performance of Er3+ doped glass at 0.55 µm emission contain different nanoparticles NPs have been comparatively evaluated. Glass containing 1.0 mol % of Er3+ doped with different NPs (Ag, Co and Fe ) have been prepared using melt quenching technique. X-ray diffraction analysis reveals the all the prepared samples are amorphous. The UV-Vis absorption spectra of all glasses show several prominent peaks at 525 nm, 660 nm, 801nm, 982 nm and 959 nm due to transition from ground state4I15/2 to different excited of2H11/2,4F9/2,4I9/2,4I11/2, and4I13/2. The emission of Er3+ at 0.55 µm for glass contain Ag NP shows significant enhancement about 3 folds up to 0.6 mol%. On the other hand, the emission of Er3+ at 0.55 µm for glass containing Fe NPs and Co NPs intensely quench probably due to the energy-transfer from Er3+ ion to NPs and magnetic contributions