Beam-quality factor of single-mode gain-guided fiber lasers

The beam-quality factor M(2) for the fundamental LP01 mode of a step-index fiber is calculated in the presence of gain, in a closed form, as a function of the complex generalized V number. It is shown that the M(2) value of a single-mode gain-guided fiber laser can be arbitrarily large. The results are important for the interpretation of the beam-quality measurements in recent experiments on single-mode gain-guided fiber lasers.     

Essential oil from aerial parts of of Betonica grandiflora Willd. from Iran

The chemical composition of the essential oil obtained from the aerial parts of Betonica grandiflora Willd., growing wild in Iran, was analysed by gas chromatography-mass spectrometry for the first time. Overall, 40 volatile components were identified on the basis of their mass spectra characteristics and retention indices in which ledol (21.8%), myrtenyl acetate (21.7%), eudesm-7(11)-en-4-ol (6.5%), trans-caryophyllene (5.5%), α-bisabolol (4.9%) and isolongifolol (4.5%) were the major constituents. Oxygenated sesquiterpenes, monoterpene hydrocarbons and sesquiterpene hydrocarbons were the main groups of compounds with 45.6%, 23.1% and 18.4%, respectively. The oil was moderately active against Bacillus subtilis and Staphylococcus aureus and inactive against Enterococcus faecalis and Klebsiella pneumoniae.