Population mechanisms of the green Er3+:LiYF4 laser

In computer simulations the mechanisms that lead to room-temperature continuous-wave green upconversion lasing in Er3+:LiYF4 are investigated. The rate-equation system considers the full erbium level scheme up to 2H9/2, ground-state depletion, excited-state absorption on the pump and laser wavelengths, three interionic processes, stimulated emission, and the crystal and resonator data of the experiments. Experimental results performed at the University of Hamburg, Germany, are reproduced in the simulation. The influence of different parameters as pump wavelength, absorption cross sections, interionic parameters, dopant concentration, and temperature is investigated. An avalanche effect which exploits the strong cross relaxation from the upper laser level and the upconversion from 4I13/2 leads to an efficient population of the upper laser level. At higher dopant concentrations the cross relaxation becomes detrimental to stimulated emission due to the depletion of the upper laser level. This concentration dependence can be considered as a general behavior of rare-earth-doped avalanche lasers

Excited-state absorption in ZBLAN:Er3+: implications for a diode-pumped 3-µm fiber laser

Effective excited-state absorption (ESA) cross-sections are measured in ZBLAN:Er3+ at 780-840 nm. Pump losses by ESA are present over the whole absorption band. Diode pumping at 979 nm seems more favorable for high-power 3-µm fiber lasers

Human pharmacology of 5-epi-sisomicin (Sch 22591) following intramuscular administration

5-epi-sisomicin was given as a single intramuscular injection of 1 mg/kg to six healthy male adults. Serum peak concentrations averaged 3.07 mg/l, the mean elimination half life was 179 min and the mean 24 h urinary recovery was 85.3%. Local and systemic tolerance was goo

Investigations on the slope efficiency of a pulsed 2.8-µm Er3+:LiYF4 laser

A slope efficiency of 40% from an Er3+:LiYF4 laser is demonstrated under pulsed Ti:sapphire pumping at 973 nm. With reduction of the pump-pulse duration a significant decrease of the slope efficiency and an increase of the threshold is observed in the experiment and confirmed with high accuracy in a computer simulation. This behavior is due to interionic upconversion from the lower laser level, which leads to energy recycling into the upper laser level. The upconversion rate is negative at threshold but increases strongly with rising pump pulse energy, thus enhancing the slope efficiency. The conditions are derived that are necessary for achieving the high slope efficiency of the energy-recycling regime

150 mW unsaturated output power at 3 µm from a single-mode-fiber erbium cascade laser

We report on an erbium cascade laser in a fluorozirconate fiber. Lasing on the transition 4I11/2 -> 4I13/2 at 2.71 µm is supported by colasing on the transition 4S3/2 -> 4I9/2 at 1.72 µm. This recycles the excitation that is lost via excited-state absorption and avoids the saturation of the output power. Threshold at 2.71 µm is 33 mW launched pump power at 791 nm. The measured slope efficiency of 22.6% is relatively close to the 29.1% stokes-efficiency limit. An output power of 158 mW is obtained, limited only by the 1.43 W power available from the Ti:sapphire pump laser. Output power is 15 and slope efficiency 2.5 times higher than reported in previous publications

Serological diagnosis of Q fever endocarditis

The diagnosis of Q fever endocarditis cannot be made by bacterial cultures and necessitates serological identification of specific antibodies to Coxiella burnetii which stimulates mainly the production of anti-phase II antibodies during the acute diséase, but primarily anti-phase I antibodies in endocarditis. Indirect micro-immunofluorescence allows rapid detection of specific IgA, IgG and IgM. The results of serological analyses of 191 acute cases of Q fever were compared with those of 8 cases of Coxiella burnetii endocarditis. All sera were evaluated by complement fixation and microimmunofluorescence tests. The highest titre differences between primary Q fever and Q fever endocarditis were observed with anti-phase IIgA and IgG antibodies measured by microimmunofluorescence followed by anti-phase I antibodies measured by complement fixation tests. Anti-phase IIgG and IgM titres were consistently higher than anti-phase II titres in endocarditis. The reverse is true in acute Q fever. In addition, anti-phase I Ig A appeared to be diagnostic for Coxiella burnetii endocarditis. Accordingly we recommend the testing of these specific IgA, IgG, and IgM by microimmunofluorescence in cases of culture-negative endocarditis. These tests could also prove useful for following the development of Coxiella burnetii endocarditis in patients under treatmen