Concentration quenching of luminescence lifetime in ytterbium-doped potassium double tungstate waveguide amplifiers

Integrated optical amplifiers employing ytterbium-doped potassium double tungstates exhibit an ultra-high peak gain exceeding 1000 dB/cm, in addition to a broad gain of up to 150 dB/cm over a 55-nm wavelength range. Here we report a study of the luminescence lifetime in samples spanning a broad range of dopant concentrations (1.2−57.5 at.%). By use of the pinhole method, elongation of the luminescence lifetime due to radiation trapping is avoided, providing a more accurate analysis of concentration quenching of the luminescence lifetime, which directly influences the waveguide amplifier performance and can, in principle, inhibit scaling of the gain with increasing dopant concentration

Metabolismo urbano de nutrientes: reúso y compostaje de residuos asociados con la porcicultura en Ciudad Juárez

Se documentan las prácticas de manejo y los volúmenes de residuos orgánicos asociados con la porcicultura periurbana (escamocha y excretas), así como el manejo de las podas municipales que permitirían cerrar ciclos biogeoquímicos en Ciudad Juárez. Se determinó que, con 177 toneladas al año, existen suficientes podas municipales para compostar las 1967 toneladas anuales de excretas porcinas generadas, y que existe tanto la necesidad como la superficie suficiente para utilizar ese compost en las áreas verdes municipales. En este análisis parcial del metabolismo urbano de la ciudad, se demuestra que se tienen cubiertos los requisitos para el establecimiento del proceso de compostaje en la localidad (el interés de los actores, la experiencia en el proceso, la infraestructura mínima)

Exploring the transferability of large supramolecular assemblies to the vacuum-solid interface

We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111) surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces. The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111) surface under ultra-high vacuum conditions; the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly, suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation. This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface

Highly Yb-doped KGd(WO₄)₂ thin-film amplifier

We report record-high small-signal gain of 1050 dB/cm at 981 nm wavelength in a KGd0.425Yb0.575(WO4)2 thin film. The sensitivity of gain to the shift of beam-focus position, which is critical under non-waveguiding conditions, is investigated

La traducción del lenguaje soez para el doblaje de la película Chicas Pesadas

This article presents the results of an analysis applied to the dubbing of the movie Mean Girls, whose lexical content is abundant in foul language, which has historically been the subject of discussion, which has led to attenuation strategies and even censorship. For this, a content analysis of the dialogues was carried out in which it was sought to determine in which cases there is a greater distance between the original message and the converted message. The results showed that no excessive attenuation or omission of this type of language was implemented, although some changes were achieved in response to the cultural differences between American English and Latin Spanish.Este artículo presenta los resultados de un análisis aplicado al doblaje de la película Chicas Pesadas, cuyo contenido léxico es abundante en lenguaje soez, el cual ha sido motivo de discusión históricamente, lo que ha llevado a estrategias de atenuación e incluso censura. Para ello, se realizó un análisis de contenido de los diálogos en el que se buscó determinar en qué casos existe una mayor distancia entre el mensaje original y el mensaje traducido. Los resultados mostraron que no se implementó un exceso de atenuación u omisión de este tipo de lenguaje, si bien se realizaron ciertos cambios en respuesta a las diferencias culturales presentes entre el inglés americano y el español latino.&nbsp

Spiral amplifiers in a-Al₂O₃:Er on a silicon chip with 20 dB internal net gain

Spiral-waveguide amplifiers in erbium-doped amorphous aluminum oxide are fabricated by RF reactive co-sputtering of 1-µm-thick layers onto a thermally-oxidized silicon wafer and chlorine-based reactive ion etching. The samples are overgrown by a SiO2 cladding. Spirals with several lengths ranging from 13 cm to 42 cm and four different erbium concentrations between 0.5-3.0×10^20 cm^-3 are experimentally characterized. A maximum internal net gain of 20 dB in the small-signal-gain regime is measured at the peak emission wavelength of 1532 nm for two sample configurations with waveguide lengths of 13 cm and 24 cm and erbium concentrations of 2×10^20 cm^-3 and 1×10^20 cm^-3, respectively. The obtained gain improves previous results by van den Hoven et al. in this host material by a factor of 9. Gain saturation as a result of increasing signal power is investigated. Positive net gain is measured in the saturated-gain regime up to ~100 µW of signal power, but extension to the mW regime seems feasible. The experimental results are compared to a rate-equation model that takes into account migration-accelerated energy-transfer upconversion (ETU) and a fast quenching process affecting a fraction of the erbium ions. Without these two detrimental processes, several tens of dB/cm of internal net gain per unit length would be achievable. Whereas ETU limits the gain per unit length to 8 dB/cm, the fast quenching process further reduces it to 2 dB/cm. The fast quenching process strongly deteriorates the amplifier performance of the Al2O3:Er3+ waveguide amplifiers. This effect is accentuated for concentrations higher than 2×10^20 cm^-3