Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission.

We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime's coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.

Species status of Colias misti (Pieridae: Coliadinae) from the Arequipa region, South Peru, and a description of its new subspecies, from Cotahuasi canyon, South-Central Peru.

A new species of the genus Colias Fabricius from the Arequipa region of Peru, C. misti Kir'yanov sp. nov., stat. nov., is established by raising it from the subspecies rank, C. lesbia misti Kir'yanov 2017. This taxonomic act is justified after detailed comparison of C. misti with representatives of phenotypically similar other South American Colias, including the subspecies of C. lesbia. The newly presented taxa are diagnosed by adult morphology, bionomics, and male genitalia. The diagnosis of a new subspecies Colias misti ccota Kir'yanov ssp. nov., discovered in the World's deepest canyon Cotahuasi (Peru), is based on different and stable characters in phenotypes, genitalia, and bionomics of C. misti ccota and C. misti misti. Both subspecies of C. misti are endemic to the Western slopes of the Andes. It is also demonstrated that the shape of the male aedeagus is diagnostic for a reliable identification of the South American Colias.

Influence of electron irradiation on optical properties of Bismuth doped silica fibers.

We report a study of the attenuation spectra transformations for a series of Bismuth (Bi) doped silica fibers with various contents of emission-active Bi centers, which arise as the result of irradiation by a beam of high-energy electrons. The experimental data reveal a substantial decrease of concentration of the Bi centers, associated with the presence of Germanium in silica glass, at increasing the irradiation dose (the resonant-absorption bleaching effect in germano-silicate fiber). In contrast, the spectral changes that appear in Bi doped alumino-silicate fiber have through irradiation a completely different character, viz., weak growth of the resonant-absorption peaks ascribed to the Bi centers, associated with the presence of Aluminum in silica glass. These results demonstrating high susceptibility of Bi centers to electron irradiation while opposite routes of the irradiation-induced spectral changes in Bi doped germanate and aluminate fibers seem to be of worth notice for understanding the nature of these centers.