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Fluorescence experiments have been performed to study the interaction of 193-nm laser radiation with dielectric thin films of LaF/sub 3/, AlF/sub 3/, and MgF/sub 2/. Spectral- and time-resolved measurements reveal the presence of cerium in LaF/sub 3/ and the influence of hydrocarbons in MgF/sub 2/ and LaF/sub 3/. Virtually no fluorescence response is observable in the case of AlF/sub 3/. Supplementary measurements on multilayer stacks confirm the contribution of hydrocarbon and cerium emission in high-reflective UV mirrors upon ArF excimer laser irradiation. Energy density dependent measurements indicate a linear absorption process as the origin of UV laser induced fluorescence in LaF/sub 3/. Luminescence calculations are applied as a helpful tool in order to account for interference effects that are inherently to be found in the multilayer emission spectra.

Time-resolved luminescence experiments have been set up in order to study the interaction of 193-nm laser radiation with dielectric thin films. At room temperature, Al/sub 2/O/sub 3/ coatings show photoluminescence upon ArF excimer laser irradiation, with significant intensity contributions besides the known substrate emission. Time- and energy-resolved measurements indicate the presence of oxygen-defect centers in Al/sub 2/O/sub 3/ coatings, which suggests a strong single- photon interaction at 193 nm by F/sup +/ and F center absorption. Measurements on highly reflective thin-film stacks, consisting of quarter-wave Al/sub 2/O/sub 3/ and SiO/sub 2/ layers, indicate similar UV excitations, mainly from color centers of Al/sub 2/O/sub 3/

Small oscillations of surface electrons that manipulate light on the nanoscale could be the route to applications as disparate as faster computer chips and cures for cancer. Joerg Heber reports.

Thin films of oxygen-bearing compounds could have myriad practical applications, finds Joerg Heber, if a few problems can be overcome.

Although the Internet has fundamentally changed the way we communicate, science publishing is remarkably hesitant in making full use of the potential offered by new technology.

The 2014 Nobel Prize in Physics has been awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources."

Recent interest in intersubband (IS) transitions in semiconductor heterostructures with large band offset has been fueled by attempts to extend the wavelength range of IS-based optical devices to the fiber-optics wavelength range around ~ 1.55 μm. GaN/AlGaN-based heterostructures are of particular interest due to their large effective electron mass and large longitudinal optical phonon energy. Both are essential to achieve ultrafast electron relaxation at large transition energies. IS absorption in GaN/AlGaN single and coupled double quantum wells (DQWs) has been measured. The samples were grown by molecular beam epitaxy on sapphire substrate and with a large (0.65 or 0.9) AlN-mole fraction in the barriers. Peak absorption wavelengths as short as 1.35 μm and 1.52 μm were measured for a symmetric DQW of 12 Å wide wells coupled by a 10 Å wide barrier, which also showed evidence of excited-state anti-crossing. As expected, asymmetric DQWs displayed no such anti-crossing, and the ground-state anti-crossing energies were found to be much smaller – as a result of the comparatively large effective electron mass – than the energy broadening of individual transitions. The asymmetric DQWs displayed peak absorption wavelengths between 1.5 and 2.9 μm. The electron relaxation time, attributed to longitudinal optical phonon scattering has been measured by pump-probe technique as 240 fs for a coupled DQW sample.

Despite the good education of its scientists, science and technology in Mexico faces multiple challenges, says Juan Ramon de la Fuente, a former Minister of Health and former Rector of the National Autonomous University of Mexico.