T. Hinklin

Ultrafine titania by flame spray pyrolysis of a titanatrane complex

Ultrafine titania particles can be produced by flame spray pyrolysis of a chelated metal alkoxide. The precursor can be made by reacting a titanium hydrosol with triethanolamine in ethylene glycol. The chelate, dissolved in ethanol, is misted as an aerosol into an oxidizing flame where it undergoes combustion. The combustion process generates particles, probably by a gas phase condensation process, that are discrete single crystals that exhibit some faceting. The powder is a mixture of anatase and rutile (<10%), with a 45±5 m2 g−1 BET surface area. The calculated equivalent spherical diameter (34+4 nm) is consistent with typical particle sizes found in TEM micrographs. The particles are briefly compared with commercial ultrafine particles produced by flame hydrolysis of TiCl4 and by Ti vapor condensation.

Continuous-wave ultraviolet laser action in strongly scattering Nd-doped alumina

We report electrically pumped, cw laser action near 405 nm from Nd(3+) -doped delta -alumina nanopowders. To our knowledge, this is the first report of stimulated emission from the high-lying F(2) -excited states, achieved through feedback from strong elastic scattering of light over transport path lengths shorter than half a wavelength.

Ultraviolet emission and Fano resonance in doped nano-alumina

Emission properties of Al2O3 nanopowders, synthesized by flame spray pyrolysis with Mg, Cr, and Sc dopants, are investigated, principally in the protein lysing range of 250–290nm (UV-C band). As expected, point defect densities depend on crystal phase and irradiation history and strongly influence emission properties at short wavelengths. Ultraviolet and visible emission intensities of aggregated point defect centers change upon electron beam exposure at high current densities, but ultraviolet emission from point defects is persistently enhanced over a narrow range of Mg-doped Al2O3 compositions slightly off spinel stoichiometry. At 40% Mg concentration, emission intensities at 320nm rise by over an order of magnitude after beam exposure. Quantum efficiency for cathodoluminescence in the 250–300nm range nevertheless remains low. Point defect ionization at high currents shifts the emission of Al2O3 nanopowders to the infrared and is shown to be correlated with a ubiquitous Fano resonance in ionized Cr-vaca...

Electrical generation of stationary light in random scattering media

In recent years there has been great interest in controlling the speed of propagation of electromagnetic waves. In gases and crystals, coherent techniques have been applied to alter the speed of light without changing the physical or chemical structure of the medium. Also, light transmitted by highly disordered solids has exhibited signatures of Anderson localization, indicating the existence of a regime of “stopped” light that is mediated by random elastic scattering. However, to date, light has not been generated in a random medium as a pointlike excitation that is fixed in space from the outset. Here we report experimental evidence for the electrical generation and confinement of light within nanosized volumes of a random dielectric scattering medium in which a population inversion has been established, and discuss the properties of these novel light sources.