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An unusual almost flat broadband plasmonic absorption, ranging from 400nm to well beyond 2500nm, was observed in a 150nm thin film of Ag nanoparticles embedded in a Teflon AF® matrix. The nanocomposites were synthesized by a simple single-step vapor-phase codeposition method. The Ag nanoparticles of various sizes and shapes, and thus various resonance frequencies, form a fractal percolating network. The broadband absorption, attributed to plasmon excitations within the nanoparticles, could be useful for multicolor applications in the visible and infrared wavelengths region.

We present a spectroscopic overview of Cr +-doped Y3A150» (YAG), a new laser material for the near-infrared region (NIR). It is found that only 2% of the Cr ions are tetrahedrally coordinated Cr +.However, the optical spectra are dominated by this ion. The missing inversion symmetry for the tetrahedral site causes higher cross sections than are common for octahedrally coordinated ions. The experimental data include a survey of the absorption and emission features. Lifetime measurements, as well as piezospectroscopic experiments yield additional spectroscopic information. Our data suggest an energy-level assignment that is different from the one previously used to describe the spectrum. Instead of ascribing the strong NIR absorption band, centered at around 1000 nm, to the '8&('A2) 'E('T2) transition, we assign it to the '8&('A&)~'A2('T&) transition. This assignment is able to describe the polarization-dependent spectra, the piezospectroscopic results, and the results from earlier polarizationdependent saturation experiments.An analysis of the luminescence decay rate yields quantum eSciencies of around 49% at 10 K and 15% at room temperature, resulting in a peak emission cross section of 3.5X10 19 cm2

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Luminescent europium-doped Y2O3 precursors are evaluated as potential ex situ thermal sensors for rapid heating events. The material is heated via pyroprobe for periods between 1 and 100 s. The morphological and optical properties of the material are measured as a function of heated temperature and dwell time. Upon heating, the material is believed to transform according to Y2(CO3)3 → Y2O(CO3)2 → Y2O2CO3 → Y2O3, with the transition to the crystalline Y2O3 phase occurring at about 666 °C. The optical spectra of the heat-treated samples reflect the presence of amorphous and crystalline components. The amorphous peak of the excitation spectra initially shifts to shorter wavelength and increases in width. With increasing temperature, a crystalline peak appears and grows in intensity while the amorphous peak disappears. By use of peak position and peak width, it is possible to monitor the temperature that the particles were exposed to.

Silver nanoparticles embedded in a dielectric matrix are investigated for their potential as broadband-absorbing optical sensor materials. This contribution focuses on the electrical properties of silver nanoparticles at various morphological stages. The electrical current through thin films, consisting of silver nanoparticles, was characterized as a function of film thickness. Three distinct conductivity zones were observed. Two relatively flat zones ("dielectric" for very thin films and "metallic" for films thicker than 300 -400 Å) are separated by a sharp transition zone where percolation dominates. The dielectric zone is characterized by isolated particle islands with the electrical conduction dominated by a thermally activated tunneling process. The transition zone is dominated by interconnected silver nanoclusters -a small increase of the film thickness results in a large increase of the electrical conductivity. The metallic conductivity zone dominates for thicknesses above 300 -400 Å.

Luminescent nanophase europium-doped ZrO 2 precursors are subjected to pyroprobe heating with nominal heating rates of 20 000°C/s for 1 and 10 s to various temperatures. When heated above the crystallization temperature, the material forms tetragonal and monoclinic polymorphs. Optical spectroscopy is used to measure the excitation spectra, fluorescence spectra, and fluorescence lifetimes of the heated samples. These optical signatures are evaluated for their potential as temperature indicators for short heating events. The fluorescence lifetimes and the intensity ratio of two fluorescence peaks appear to be promising temperature indicators. The fluorescence intensity ratio of two peaks at about 591 and 592 nm of the tetragonal polymorph decreases linearly with temperature and the peak position increases linearly with temperature between about 800 and 1300 K. The fluorescence lifetimes of both polymorphs increase with temperature. As the temperature reaches about 1000 K for the tetragonal phase and 1200 K for the monoclinic phase, the fluorescence lifetime starts to decrease again.