Papilionidae and pieridae butterflies (lepidoptera, papilionoidea) of the state of Guanajuato, México

An annotated list of butterflies of the families of Papilionidae and Pieridae (Lepidoptera: Papilionoidea) of the state of Guanajuato, Mexico, is presented for the first time. The list is the result of systematic monitoring of these taxa in a few localities of the state (mainly, in the vicinities of León and Guanajuato City) during 1998-2004, as well as from specimens at the Mexican National Collection of Insects. We report 12 species of Papilionidae (4 new records for the state), and 27 species of Pieridae (15 first records for Guanajuato). Therefore, at least about 30% and 50% of species of, respectively, Papilionidae and Pieridae, are registered as new state records. Some distributional and ecological observations for the butterflies are addressed as well.Presentamos, por primera vez, una lista anotada de las familias Papilionidae y Pieridae (Lepidoptera: Papilionoidea) para el estado de Guanajuato. Esta lista es el resultado de muestreos sistemáticos de estos taxones en un conjunto de localidades del estado (principalmente en las cercanías de León y la Ciudad de Guanajuato) durante 1998-2004, así como de especímenes depositados en la Colección Nacional de Insectos. Se registran 12 de Papilionidae y 27 especies de Pieridae, de las cuales 4 y 15 respectivamente son nuevos registros para el estado. Por lo anterior 30% de las especies de Papilionidae y 50% Pieridae constituyen nuevos registros estatales. Se presentan algunas observaciones de la ecología y distribución de los taxones encontrados

Resonant and thermal changes of refractive index in a heavily doped erbium fiber pumped at wavelength 980 nm

We report a theoretical and experimental study of the refractive index variation in a heavily doped erbium silica fiber within the spectral range 1500-1580 nm under the pumping at the wavelength 980 nm. The two main contributions in the refractive index change are addressed the resonant part determined by the saturation effect in the fiber and the thermal part stemming from the fiber heating due to the excited-state absorption and Stokes losses. We demonstrate that the thermal contribution in the resultant refractive index change is a notable value, which is the feature of erbium fibers with a high concentration of erbium ions

Dual-kind Q-switching of erbium fiber laser

Two different regimes of Q-switching in the same implementation of an actively Q-switched erbium-doped fiber laser are demonstrated. Depending on the active fiber length and repetition rate of an intracavity Q-cell (acousto-optic modulator), the laser operates either in the regime of common, rather long and low-power, pulses composed of several sub-pulses or in the one of very short and powerful stimulated Brillouin scattering-induced pulses. The basic physical reason of the laser system to oscillate in one of these two regimes is the existence or absence of CW narrow-line 'bad-cavity' lasing in the intervals when the Q-cell is blocked

Bose condensation in a model microcavity

We study the equilibrium properties of a system of dipole-active excitons coupled to a single photon mode at fixed total excitation. Treating the presence or absence of a trapped exciton as a two-level system produces a model that is exactly soluble. It gives a simple description of the physics of polariton condensation in optical cavities beyond the low-density bosonic regime.Comment: 5 pages, 3 figures, uses RevTeX and psfig. Revised version: (1)Corrects an error in our treatment of the constraint, leading to a rescaled transition temperature, and (2)Extends our discussion of the relevance of the model to real system

Nonsaturable absorption in alumino-silicate bismuth-doped fibers

We report an experimental and theoretical investigation of fluorescence decay and transmission coefficient at ∼1 μm pumping for a series of bismuth (Bi) doped alumino-silicate fibers with different concentrations of Bi centers. By modeling the experimental data, we show that the excited-state absorption (ESA) and up-conversion (UC) processes are responsible for a growth of nonsaturable absorption and deviation from exponential the fluorescence decay in the fibers with an increase in Bi centers content. Assuming that Bi centers ensemble is composed of subsystems of single and paired centers, and an increase in partial weight of the latter with a Bi centers concentration growth, we can successfully explain the experimental data. Also, these assumptions allow us to estimate the constants characterizing the ESA and both homogeneous and inhomogeneous UC processes in the fibers

Robustness of Quadratic Solitons with Periodic Gain

We address the robustness of quadratic solitons with periodic non-conservative perturbations. We find the evolution equations for guiding-center solitons under conditions for second-harmonic generation in the presence of periodic multi-band loss and gain. Under proper conditions, a robust guiding-center soliton formation is revealed.Comment: 5 pages, 5 figures, submitted to Optics Communicatio

Power-dependent effective reflection of fiber Bragg grating as output coupler of Ytterbium-doped fiber laser

In this paper, we discuss the effective reflection of a fiber Bragg grating and its dependence on laser power when it is used as an output coupler of an ytterbium-doped fiber laser (here the effective reflection is considered to be a part of intracavity laser power reflected by the grating back to the laser cavity). We propose and discuss an experimental technique based on spectral and power analysis and derive simple formulae that permits one to obtain the intra-cavity power and the grating effective reflection. We show that, due to spectral broadening, the effective reflection dramatically decreases with increasing laser power, the effect precisely fitted using the derived formulae describing this quantity. The experimental part of the present study is based on an analysis of the operational regime of a long-wavelength ytterbium-doped fiber laser

Spectroscopic Properties of Holmium-Aluminum- Germanium Co-doped Silica Fiber

We report the basic spectroscopic properties of a home-made holmium-aluminum-germanium co-doped silica fiber, designed for laser applications. We present the ground-state and excitedstate absorption spectra of the fiber along with the upconversion emission spectrum under laser action, which served for making an energy levels’ diagram of Ho3+ ion. We discuss the ways to assess the kinetics of Ho3+ 2-μm fluorescence, focusing on measuring fluorescence lifetime from 5I7 level and nonradiative decay time from 5I6 level. The simple analytical formulae, applicable for fitting of the fluorescence decay curve, are derived, which can be useful for precise modeling of holmiumdoped fiber lasers.PID2019-104276RB-I0

Novel Y2O3-codoped Yb/Tm-doped picosecond fiber laser

We demonstrate the novel picosecond mode-locked Y2O 3-codoped Yb/Tm-doped fiber lasers, operating at 1950 nm and producing pulses of up to 1 nJ energy, using a SESAM and an Er-doped pump fiber laser operating at the wavelength 1590 nm or a semiconductor pump laser operating at the wavelength of 1560 nm. We also report on the spectroscopic characterization of these new fibers with various compositions, identifying the optimum one for the maximum Yb/Tm energy transfer, the latter increasing with the increase of the Y concentration. The observed energy transfer between Yb and Tm makes this laser promising also for direct diode-pumping with most advanced and low cost 975 nm diodes, making this laser attractive for compact low cost picosecond Tm-doped fiber laser systems