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Radial Bragg gratings are commonly used to enhance light extraction from quantum emitters, but lack a well‐suited, fast simulation method for optimization beyond periodic designs. To overcome this limitation, an algorithm based on the transfer matrix model (TMM) to calculate the free‐space emission of such gratings is proposed and demonstrated. Using finite difference time domain (FDTD) simulations, free‐space emission, and transfer matrices of single grating components are characterized. The TMM then combines any number of components to receive the total emission. Randomized benchmarks verify that results from this method agree within 98% with FDTD while reducing simulation time by one to two orders of magnitude. The speed advantage of this approach is shown by maximizing emission of a fifteen‐trench circular grating into a Gaussian mode. It is expected that this novel algorithm will facilitate the optimization of radial gratings, enabling quantum light sources with unprecedented collection efficiencies. [ABSTRACT FROM AUTHOR]

A growing number of studies warn of the adverse health effects of indoor particulate matters (PM). However, little is known about the molecular compositions and emission characteristics of PM‐bound organics (OM) indoors, a critical group of species with highest concentration and complexity in indoor PM. In a Hong Kong residence where prescribed activities were performed with normal frequency and intensity, we found that the activities significantly elevated not only the total concentration but also the fraction of OM in indoor PM. However, the concentration of the total PM‐bound OM outdoors (10.3 ± 0.7 μg/m3) surpassed that for the indoor counterpart during the undisturbed period (8.2 ± 0.1 μg/m3), that is, period when there was no activity with high emission of PM but the residual effects of previous activities might remain. Emissions of indoor activities involving combustion or high‐temperature processes significantly elevated the indoor‐to‐outdoor (I/O) ratios for a majority of organic species. In addition, gas‐to‐particle partitioning, secondary formation, carrying‐over (residues of pollutants in the air), and re‐emission also modulated the I/O ratios of some compounds. Chemically comprehensive emission profiles of speciated organics were obtained for 5 indoor activities in the residence. While the indoor contribution to PM‐bound OM was estimated to be not higher than 13.1% during the undisturbed period, carrying‐over and/or re‐emission seemed to exist for certain compounds emitted from cigarette smoking and incense burning. This study enhances knowledge on emissions and airborne fate of speciated organics in indoor PM. [ABSTRACT FROM AUTHOR]

Morphological characteristics of Strong Thermal Emission Velocity Enhancement (STEVE) are investigated during an event on July 17, 2018. We calibrate photographs from citizen scientists for scientific purposes. We determine the altitude profiles for STEVE emissions. The spectral continuum purplish STEVE emission peaks at 200 km, which is in the altitude range where redline‐only SAR emission could be generated. The green picket fence peaks at 110 km, similar to that of the typical green aurora. For both emissions, their altitudes of the peak emissions and the shapes of the altitude profiles are similar across different longitudes. In regions of two‐layer purplish STEVE emissions, the lower layer STEVE peaks at ∼130 km with slightly different peak altitudes at different longitudes. The green picket fence structures are separated by 14 km in longitude with a full width of half maximum of ∼5.3 km. They move westward at a roughly constant speed of ∼250 m/s, although they sometimes disappear and reappear. The purplish STEVE and green picket fence emissions are latitudinally narrow, and whether they are simultaneously collocated on the same magnetic field line depends on their latitudinal offset relative to their width. We demonstrate that the green picket fence and purplish STEVE emissions are located on magnetic field lines within a tenth (0.02°) of the latitudinal width of STEVE (0.2°). The fact suggests that different STEVE emissions are driven by the same narrow region either in the ionosphere or the magnetosphere, although their generation mechanisms differ. The morphological characteristics have important implications in determining how STEVE is generated. Key Points: We obtain triangulated altitude profiles of upper and lower layer purplish Strong Thermal Emission Velocity Enhancement (STEVE) and green picket fence emissions as a function of longitudeThe peak altitudes of purplish STEVE emission (200 km) and green picket fence (110 km) do not change significantly across different longitudesSTEVE emissions map to a latitudinally narrow driver region along field line, with accuracy of one‐tenth of its latitudinal width [ABSTRACT FROM AUTHOR]

We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL). [ABSTRACT FROM AUTHOR]

This review described a noticeable feature of pulsed radio-frequency-driven glow discharge plasma for atomic emission spectrometry. The temporal response of the emission signal, generated by the pulsed discharge, comprised a sharp pre-peak and the subsequent plateau portion having smaller emission intensities each for the discharge pulse, in which the intensity of the pre-peak was 10–20 times as large as the plateau-stage intensity, depending on the discharge parameters. Suggested mechanisms for this phenomenon were introduced from several published papers, which were based on a temporal variation in a degree of self-absorption during a pulse duration, on generation of gas pressure wave, or on a transient increase of the discharge current at the initial edge of a pulse which thus elevated the gas temperature. It was also mentioned that such emission characteristics could be utilized to obtain better analytical performance in the optical emission spectrometry. A detection method, associated with the introduction of pulsed bias current, was effective for controlling the emission response from the pulsed plasma, because it totally elevated the emission intensity of the plateau portion rather than the pre-peak with little change in the background level. [ABSTRACT FROM AUTHOR]

A one-axis charge-coupled device camera-based goniometer setup was developed to measure the three-dimensional radiance profile (longitudinal, azimuthal, and polar) of cylindrical light diffusers in air and water. An algorithm was programmed to project the two-dimensional camera data onto the diffuser coordinates. The optical system was designed to achieve a spatial resolution on the diffuser surface in the submillimeter range. The detection threshold of the detector was well below the values of measured radiance. The radiance profiles of an exemplary cylindrical diffuser measured in air showed local deviations in radiance below 10% for wavelengths at 635 and 671 nm. At 808 nm, deviations in radiance became larger, up to 45%, most probable due to the manufacturing process of the diffuser. Radiance profiles measured in water were less Lambertian than in air due to the refractive index matching privileging the radial decoupling of photons from the optical fiber. [ABSTRACT FROM AUTHOR]

. Cylindrical light diffusers are commercially available for clinical applications such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A fluorescence imaging technique has been used to quantify the light distribution produced by each of six different diffuser fibres. The light distribution produced by each device was found to depend on the distance the light propagated in the fluorescent dye solution. At a distance of 1 mm from the diffuser midline, the measured profiles were found to be consistent with published results obtained in air at a similar distance. The three devices intended for PDT utilised scattering particles and reflectors in their construction. The profiles produced by these applicators revealed peaks that were attributed to the reflectors located at their distal tips. By comparison, the two etched ILP fibres displayed either a strong modulation in the profile due to non-uniform etching or a predominant forward peak associated with the conical shape of the tip. We conclude that it is important to take into account the forward-directed light emitted by the diffusers when considering clinical applications using these devices. [ABSTRACT FROM AUTHOR]

The uniformity of the emission profile produced by a cylindrical light diffuser is an important parameter for determining the light dose received by the target tissue during laser therapies such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A technique originally used for determining the profile of a laser beam with a commercial video camera is adapted in order to measure the distribution of light from a cylindrical diffuser. The method can produce quantitative one-dimensional beam profiles in both the circumferential and axial direction of the light diffuser. The system allows the use of tissue phantoms that provide a convenient and effective method for comparing manufacturer's measurements often made in air with those to be expected in vivo. The technique is a quick and easy method for assessing light diffusers before treatment, and utilises readily available equipment that does not require specialist knowledge. Also, the response of the video camera facilitates the assessment of diffusers over a relatively broad optical spectrum, which encompasses the range of wavelengths currently used for both PDT (515–675 nm) and ILP (800–1064 nm). [ABSTRACT FROM AUTHOR]