Fluorescence lifetime-resolved imaging (FLI) is a relatively new technique of fluorescence imaging whereby the spatial distribution of fluorescence decay times can be determined directly at every pixel of an image simultaneously. The fluorescence decay times of many chromophores can act as sensitive gauges of their molecular environments. By employing measurement techniques that are quantitatively related to the radiative dynamics of the dye molecules (in the nanosecond time range), additional physical parameters are available for discerning different fluorophores with disparate lifetimes, or for characterizing a single fluorophore in different surroundings. Many physical processes such as molecular aggregation, binding of dyes to macromolecular species, inclusion of chromophores in specific cellular organwelles, fluorescence resonance energy transfer, and dynamic quenching determine the excited-state lifetime of a fluorophore. The FLI technique provides a way to measure these processes directly at 103–106 pixels in an image. In addition, if image domains differ with respect to the mean fluorescence lifetime, FLI can be used to improve the contrast of a fluorescence image. By measuring the fluorescence lifetime one can determine whether fluorescence intensity differences from different locations in an image can be attributed to differences in dye concentration or whether physical spectroscopic effects such as local differences in the rate of dynamic quenching are responsible. All the above applications provide new possibilities for biology and medical diagnostics. However the speed of data acquisition and analysis in current FLI instrumentation is limited in general to several minutes; for real-time applications (in order to follow rapid changes of microscopic samples or make in vivo endoscopic medical diagnosis) the present instruments are too slow. We present here a FLI apparatus that is capable of acquiring, processing, and displaying fluorescence lifetime-resolved images in quasi-real time. We also present rapid algorithms for analyzing the data in real time.

No abstract

The waveguide strain and the surface morphologies of AlGaN-based laser heterostructures emitting in the deep UV spectral range have been investigated. In particular, the impact of the AlGaN heterostructure design on the strain relaxation as well as the effect of the growth temperature on the surface morphology were explored. We found strain-induced plastic relaxation for laser heterostructures with 130 nm thick Al0.45Ga0.55N waveguide layers, whereas pseudomorphic growth was obtained for laser heterostructures with Al0.70Ga0.30N waveguide layers. Optically pumped lasing near 280 nm was demonstrated for the coherently grown laser heterostructures. A strong correlation of the surface morphology with the waveguide growth conditions was also observed. Low growth temperatures of 900 °C lead to a high density of V-pits originating from dislocations. By increasing the growth temperatures to 1070 °C the V-pit density significantly decreases, resulting in a more than two-fold reduction of the threshold power density of optically pumped lasers.

No abstract

In this work we present the highest spatial and spectral resolution integral field observations to date of the bipolar jet from the Orion proplyd 244–440 using Multi-Unit Spectroscopic Explorer (MUSE) narrow-field mode (NFM) observations on the Very Large Telescope (VLT). We observed a previously unreported chain of six distinct knots in a roughly S-shaped pattern, and by comparing them with Hubble Space Telescope (HST) images we estimated proper motions in the redshifted knots of 9.5 mas yr−1 with an inclination angle of 73°, though these quantities could not be measured for the blueshifted lobe. Analysis of the [Fe II] and [Ni II] lines suggests jet densities on the order of ~105 cm−3. We propose that the observed S-shaped morphology originates from a jet launched by a smaller source with M★ < 0.2 M⊙ in orbital motion around a larger companion of M★ ≃ 0.5 M⊙ at a separation of 30–40 au. The measured luminosities of the knots using the [O I]λ6300 Å and [S II]λ6731 Å lines were used to estimate a lower limit to the mass-loss rate in the jet of 1.3 × 10−11 M⊙ yr−1 and an upper limit of 10−9 M⊙ yr−1, which is typical for low-mass driving sources. While the brightness asymmetry between the redshifted and blueshifted lobes is consistent with external irradiation, further analysis of the [Ni II] and [Fe II] lines suggests that photoionization of the jet is not likely to be a dominant factor, and that the emission is dominated by collisional excitation. The dynamical age of the jet compared to the anticipated survival time of the proplyd demonstrates that photoevaporation of the proplyd occurred prior to jet launching, and that this is still an active source. These two points suggest that the envelope of the proplyd may shield the jet from the majority of external radiation, and that photoionization of the proplyd does not appear to impact the ability of a star to launch a jet.

Laser-induzierte periodische Oberflächenstrukturen (LIPSS) weisen ein hohes Potenzial für Anwendungen in den Bereichen der Oberflächenfunktionalisierung auf. Die Steuerung der Richtung dieser Nanostrukturen kann nur durch Änderung der Laserpolarisation erfolgen. Auf dem Markt gibt es kein System zur automatischen Änderung der LIPSS-Orientierung. Für den industriellen Einsatz ist dies vom Vorteil, um Inhomogenität im Strukturverlauf zu vermeiden. In diesem Beitrag wird eine Systemlösung vorgestellt, indem die Steuerung der Richtung von Nanotexturen ermöglicht wird.

Context. The He I λ10830 Å line is a high excitation line which allows us to probe the material in the innermost regions of protostellar disks, and to trace both accreting and outflowing material simultaneously. Aims. We use X-Shooter observations of a sample of 107 young stars in the Lupus (1-3 Myr) and Upper Scorpius (5-10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity. Methods. We identified eight distinct profile types in the sample. We fitted Gaussian curves to the absorption and/or emission features in the line to measure the maximum velocities traced in absorption, the full-width half-maximum (FWHM) of the line features, and the Gaussian area of the features. Results. We compare the proportion of each profile type in our sample to previous studies in Taurus. We find significant variations between Taurus and Lupus in the proportion of P Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the number of emission-only and combination profile types. We examine the emission-only profiles in our sample individually and find that most sources (nine out of 12) with emission-only profiles are associated with known jets. When examining the absorption features, we find that the blue-shifted absorption features appear less blue-shifted at disk inclinations close to edge-on, which is in line with past works, but no such trend with inclination is observed in the sources with only red-shifted features. Additionally, we do not see a strong correlation between the FWHM and inclination. Higher accretion rates were observed in sources with strong blue-shifted features which, along with the changes in the proportions of each profile type observed in the two regions, indicates that younger sources may drive stronger jets or winds. Conclusions. Overall, we observe variations in the proportion of each He I λ10830 Å profile type and in the line properties which indicates an evolution of accretion and ejection signatures over time, and with source properties. These results confirm past works and models of the He I λ10830 Å line, but for a larger sample and for multiple star-forming regions. This work highlights the power of the He I λ10830 Å line as a probe of the gas in the innermost regions of the disk.