Visible laser operation of Pr3+-doped fluoride crystals pumped by a 469 nm blue laser

French National Research Agency (ANR)We report continuous-wave (CW) laser operation of Pr3+-doped LiLuY4, LiYF4 and KY3F10 single crystals in the Red, Orange and Green spectral regions by using a new pumping scheme. The pump source is an especially developed compact, slightly tunable and intracavity frequency-doubled diode-pumped Nd:YAG laser delivering a CW output power of 0.9W at 469.12 nm. At this pump wavelength, efficient room temperature laser emissions corresponding to the P-3(0)-> F-3(2), P-3(0)-> H-3(6) and P-3(1)-> H-3(5) Pr3+ transitions are observed. While a maximum slope efficiency of 45% is obtained in the red with Pr:LiYF4, the demonstration is made for the first time of the orange laser operation of Pr:KY3F10 at about 610 nm. (C) 2011 Optical Society of Americ

A Ce: LiCAF UV laser pumped by an intracavity frequency-doubled radiation at 532 nm

We examine here the lasing conditions of a Ce: LiCAF laser crystal placed intracavity with a BBO nonlinear crystal and pumped longitudinally throughout an input dichroic mirror by the 532 nm radiation of a frequency-doubled diode-pumped Nd: YAG laser. The comparison with the results obtained with an off-axis configuration shows lower laser slope efficiencies but similar laser performance in terms of threshold absorbed pump fluences (around 200 mJ/cm 2). A model based on revisited spectroscopic parameters is developed to account for these laser performance

Human-like PB2 627K Influenza Virus Polymerase Activity Is Regulated by Importin-α1 and -α7

Influenza A viruses may cross species barriers and transmit to humans with the potential to cause pandemics. Interplay of human- (PB2 627K) and avian-like (PB2 627E) influenza polymerase complexes with unknown host factors have been postulated to play a key role in interspecies transmission. Here, we have identified human importin-α isoforms (α1 and α7) as positive regulators of human- but not avian-like polymerase activity. Human-like polymerase activity correlated with efficient recruitment of α1 and α7 to viral ribonucleoprotein complexes (vRNPs) without affecting subcellular localization. We also observed that human-like influenza virus growth was impaired in α1 and α7 downregulated human lung cells. Mice lacking α7 were less susceptible to human- but not avian-like influenza virus infection. Thus, α1 and α7 are positive regulators of human-like polymerase activity and pathogenicity beyond their role in nuclear transport

Activation of Type I and III Interferon Signalling Pathways Occurs in Lung Epithelial Cells Infected with Low Pathogenic Avian Influenza Viruses

The host response to the low pathogenic avian influenza (LPAI) H5N2, H5N3 and H9N2 viruses were examined in A549, MDCK, and CEF cells using a systems-based approach. The H5N2 and H5N3 viruses replicated efficiently in A549 and MDCK cells, while the H9N2 virus replicated least efficiently in these cell types. However, all LPAI viruses exhibited similar and higher replication efficiencies in CEF cells. A comparison of the host responses of these viruses and the H1N1/WSN virus and low passage pH1N1 clinical isolates was performed in A549 cells. The H9N2 and H5N2 virus subtypes exhibited a robust induction of Type I and Type III interferon (IFN) expression, sustained STAT1 activation from between 3 and 6 hpi, which correlated with large increases in IFN-stimulated gene (ISG) expression by 10 hpi. In contrast, cells infected with the pH1N1 or H1N1/WSN virus showed only small increases in Type III IFN signalling, low levels of ISG expression, and down-regulated expression of the IFN type I receptor. JNK activation and increased expression of the pro-apoptotic XAF1 protein was observed in A549 cells infected with all viruses except the H1N1/WSN virus, while MAPK p38 activation was only observed in cells infected with the pH1N1 and the H5 virus subtypes. No IFN expression and low ISG expression levels were generally observed in CEF cells infected with either AIV, while increased IFN and ISG expression was observed in response to the H1N1/WSN infection. These data suggest differences in the replication characteristics and antivirus signalling responses both among the different LPAI viruses, and between these viruses and the H1N1 viruses examined. These virus-specific differences in host cell signalling highlight the importance of examining the host response to avian influenza viruses that have not been extensively adapted to mammalian tissue culture

Energy transfer between Jahn-Teller systems in RbMnF3

Energy transfer in RbMnF3 was studied by time-resolved spectroscopy of 4T1g exciton and trap luminescence. Uniaxial stress was used to lift the orientational degeneracy of the Jahn-Teller distorted MnF6 octahedra. Stress also reduces the excitonic transfer rates considerably. The most drastic reduction of transfer and a nonexponential decay was observed with (110) stress. Evidence for two-dimensional transfer under (110) stress is given by computer simulation of random-walk processes and by a calculation of nearest-neighbour transfer integrals

THE TUNABLE VIBRONIC LASER MATERIALS BASED ON TRANSITION METAL IONS : SEARCH OF NEW SYSTEMS AND EXCITED STATE SPECTROSCOPY

For they are stable and they allow to get intense and tunable radiations in a large spectral domain, the vibronic solid state laser materials based on transition metal ions such as Ti3+, Cr3+, V2+, Ni2+ and Co2+ give rise presently to a renewed and increased interest, and more particularly in our laboratory as concerns the optical studies

A NEW GENERATION OF LASER ACTIVE IONS FOR TUNABLE LASER OPERATION : THE TRANSITION - METAL IONS IN TETRAHEDRAL COORDINATION

We report the polarized absorption spectra, and the emission or stimulated emission cross-section spectra of several Cr4+, Mn5+ and Co2+ doped crystals. The emission lifetimes as a function of temperature are repported as well