Cr:LiSrAlF6 channel waveguides as broadband fluorescence sources

We report on the production and fluorescence of active channel waveguides in Cr:LiSrAlF6. We have produced ∼10μm wide and 5μm high channel waveguides by He+ ion implantation, lithographic patterning and subsequent Ar+ ion sputtering. Diode-pumped waveguides emitted 13μW of fluorescence light with a spectrum ranging from 760nm to 900nm at a pump power of 165mW and a pump wavelength of 660nm. The compact and cheap optical pump source is a main advantage of this fluorescence material. This makes Cr:LiSrAlF6 channel waveguides a suitable candidate for a broadband fluorescence source in low-coherence interferometry and other applications in the near-infrared wavelength rang

SCIAMACHY validation by aircraft remote measurements: design, execution, and first results of the SCIA-VALUE mission

International audienceFor the first time three different remote sensing instruments ? a sub-millimeter radiometer, a differential optical absorption spectrometer in the UV-visible spectral range, and a lidar ? were deployed aboard DLR's meteorological research aircraft Falcon 20 to validate a large number of SCIAMACHY level 2 and off-line data products such as O3, NO2, N2O, BrO, OClO, H2O, aerosols, and clouds. Within two main validation campaigns of the SCIA-VALUE mission (SCIAMACHY VALidation and Utilization Experiment) extended latitudinal cross-sections stretching from polar regions to the tropics as well as longitudinal cross sections at polar latitudes at about 70° N and the equator have been generated. This contribution gives an overview over the campaigns performed and reports on the observation strategy for achieving the validation goals. We also emphasize the synergetic use of the novel set of aircraft instrumentation and the usefulness of this innovative suite of remote sensing instruments for satellite validation

Revisiting the hemispheric asymmetry in mid-latitude ozone changes following the Mount Pinatubo eruption: A 3-D model study

Following the eruption of Mt. Pinatubo, satellite and in-situ measurements showed a large enhancement in stratospheric aerosol in both hemispheres, but significant mid-latitude column O3 depletion was observed only in the north. We use a three-dimensional chemical transport model to determine the mechanisms behind this hemispheric asymmetry. The model, forced by European Centre for Medium-Range Weather Forecasts ERA-Interim reanalyses and updated aerosol surface area density, successfully simulates observed large column NO2 decreases and the different extents of ozone depletion in the two hemispheres. The chemical ozone loss is similar in the northern (NH) and southern hemispheres (SH), but the contrasting role of dynamics increases the depletion in the NH and decreases it in the SH. The relevant SH dynamics are not captured as well by earlier ERA-40 reanalyses. Overall the smaller SH column O3 depletion can be attributed to dynamical variability and smaller SH background lower stratosphere O3 concentrations

Reconciliation of halogen-induced ozone loss with the total-column ozone record

The observed depletion of the ozone layer from the 1980s onwards is attributed to halogen source gases emitted by human activities. However, the precision of this attribution is complicated by year-to-year variations in meteorology, that is, dynamical variability, and by changes in tropospheric ozone concentrations. As such, key aspects of the total-column ozone record, which combines changes in both tropospheric and stratospheric ozone, remain unexplained, such as the apparent absence of a decline in total-column ozone levels before 1980, and of any long-term decline in total-column ozone levels in the tropics. Here we use a chemistry–climate model to estimate changes in halogen-induced ozone loss between 1960 and 2010; the model is constrained by observed meteorology to remove the effects of dynamical variability, and driven by emissions of tropospheric ozone precursors to separate out changes in tropospheric ozone. We show that halogen-induced ozone loss closely followed stratospheric halogen loading over the studied period. Pronounced enhancements in ozone loss were apparent in both hemispheres following the volcanic eruptions of El Chichon and, in particular, Mount Pinatubo, which significantly enhanced stratospheric aerosol loads. We further show that approximately 40% of the long-term non-volcanic ozone loss occurred before 1980, and that long-term ozone loss also occurred in the tropical stratosphere. Finally, we show that halogen-induced ozone loss has declined by over 10% since stratospheric halogen loading peaked in the late 1990s, indicating that the recovery of the ozone layer is well underway

Finite-wavevector Jahn-Teller-pairing and superconductivity in the cuprat es

A model interaction is proposed in which pairing is caused by a non-local Jahn-Teller (JT) -like instability due to the coupling between planar O states and knot equal to 0 phonons. Apart from pairing, the interaction is found to naturally allow metallic stripe formation. The consequences of the model for superconductivity in the cuprates are discussed. The model is shown to be consistent with numerous sets of experimental data in quite some detail.Comment: 20 pages, 6 ps figure