1.55 μm direct bandgap electroluminescence from strained n-Ge quantum wells grown on Si substrates

Electroluminescence from strained n-Ge quantum well light emitting diodes grown on a silicon substrate are demonstrated at room temperature. Electroluminescence characterisation demonstrates two peaks around 1.55 μm and 1.8 μm, which correspond to recombination between the direct and indirect transitions, respectively. The emission wavelength can be tuned by around 4% through changing the current density through the device. The devices have potential applications in the fields of optical interconnects, gas sensing, and healthcare

In vivo imaging of the tonoplast intrinsic protein family in Arabidopsis roots

Background: Tonoplast intrinsic proteins (TIPs) are widely used as markers for vacuolar compartments in higher plants. Ten TIP isoforms are encoded by the Arabidopsis genome. For several isoforms, the tissue and cell specific pattern of expression are not known. Results: We generated fluorescent protein fusions to the genomic sequences of all members of the Arabidopsis TIP family whose expression is predicted to occur in root tissues (TIP1;1 and 1;2; TIP2;1, 2;2 and 2;3; TIP4;1) and expressed these fusions, both individually and in selected pairwise combinations, in transgenic Arabidopsis. Analysis by confocal microscopy revealed that TIP distribution varied between different cell layers within the root axis, with extensive co-expression of some TIPs and more restricted expression patterns for other isoforms. TIP isoforms whose expression overlapped appeared to localise to the tonoplast of the central vacuole, vacuolar bulbs and smaller, uncharacterised structures. Conclusion: We have produced a comprehensive atlas of TIP expression in Arabidopsis roots, which reveals novel expression patterns for not previously studied TIPs

Germanium Plasmonic Nanoantennas for Third-Harmonic Generation in the Mid Infrared

We explore the nonlinear optical properties of plasmonic semiconductor antennas resonant in the mid infrared. The nanostructures are fabricated on silicon substrates from heavily doped germanium films with a plasma frequency of 30 THz, equivalent to a wavelength of 10 μm. Illumination with ultrashort pulses at 10.8 μm produces coherent emission at 3.6 μm via third-harmonic generation

Optical activation of germanium plasmonic antennas in the mid-infrared

Impulsive interband excitation with femtosecond near-infrared pulses establishes a plasma response in intrinsic germanium structures fabricated on a silicon substrate. This direct approach activates the plasmonic resonance of the Ge structures and enables their use as optical antennas up to the mid-infrared spectral range. The optical switching lasts for hundreds of picoseconds until charge recombination redshifts the plasma frequency. The full behavior of the structures is modeled by the electrodynamic response established by an electron-hole plasma in a regular array of antennas

Nuevos estudios sobre radiación nocturna en Cachi

Se han realizado varias campañas de medidas de radiación nocturna en Cachi, Valles Calchaquíes, con el propósito de obtener un mejor conocimiento de esta cantidad en la zona. Los datos fueron utilizados para mejorar una correlación anterior de la emisividad de cielo y para proponer una nueva regresión basada en la depresión nocturna de temperaturas. Se han utilizado datos de los meses de Julio, Mayo y Septiembre en distintos años (1990, 1996, 2003, 2004). La correlación obtenida para la emisividad se aparta en un 6 % del promedio nocturno medido mientras que las derivadas para la depresión nocturna tienen una gran dispersión. Se dan las expresiones encontradas y se discute su bondad.Several campaigns to measure nocturnal radiation in Cachi, Valles Calchaquíes, were made with the proposal of getting a better knowledge of this quantity in the zone. The data were used to enhance a prior correlation of sky emissivity and to propose a new regression based on the night temperature depression. Data of months of July, May and September in different years (1990, 1996, 2003, 2004) were employed. The obtained correlation for the emissivity is 6% apart of the nocturnal average measured whereas the derived for the nocturnal depression have a great dispersion. The expressions founded are given and their kindnesses are discussed.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Depresión nocturna en Salta

Para evaluar la capacidad de enfriamiento de la atmósfera se trabajó sobre una nueva regresión basada en la depresión de temperaturas en función de la temperatura de rocío, como ya se había realizado en Cachi. Se han utilizado datos de medidas realizadas entre 1989 y 2006. La correlación obtenida para la depresión nocturna da una forma rápida de obtener la temperatura de cielo y con ello la radiación nocturna recibida. Se da la expresión encontrada y se discute su bondad con medidas realizadas en el año 2007.To evaluate the cooling capacity from the atmosphere a new regression was worked on based in the temperature depression against the dew point temperature, like it was made in Cachi. Data measures between 1989 and 2006 were used. The achieved correlation for the nocturnal depression give a quick way to obtain the sky temperature y with it, the nocturnal radiation received. The encountered expression was given and its kindness is discussed using measures made during year 2007.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Evolución de la temperatura de rocío para el cálculo de la emisividad media

Con el objetivo de disponer de una primera información sobre emisividad de cielo claro para cálculos, balances radiativos, etc. para Salta y zona del valle de Lerma, se buscó una correlación para el promedio mensual de la temperatura de rocío. En base a medidas realizadas entre 2003 y 2007 se obtuvieron dos expresiones con las cuales se llega a resultados similares, ninguno de los cuales se aparta más allá de un 5 % respecto de las medidas. Se presentan las correlaciones obtenidas, las emisividades predichas a través de ellas y la comparación de éstas con trabajos anteriores.With the objective of having a first sight about the clear sky emissivity to use in radiative balances, etc. for Salta and the Lerma valley, a correlation for the monthly averaged dew point temperature was searched. Based on measures done between 2003 and 2007 two expressions were obtained with similar results, none of them separate more than 5 % of the measures. The obtained correlations, the predicted emissivities calculated with them and a comparison with a previous work were given.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Mid-Infrared Plasmonic Platform Based on n-Doped Ge-on-Si: Molecular Sensing with Germanium Nano-Antennas on Si

CMOS-compatible, heavily-doped semiconductor films are very promising for applications in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in this wavelength range. In this work we investigate n-type doped germanium epilayers grown on Si substrates. We design and realize Ge nanoantennas on Si substrates demonstrating the presence of localized plasmon resonances, and exploit them for molecular sensing in the mid-infrared

Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  1019 cm−3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  1020 cm−3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved