Geometric system analysis of ILMD-based LID measurement systems using Monte-Carlo simulation

Imaging Luminance Measuring Device (ILMD) based luminous intensity distribution measurement systems are an established method for measuring the luminous intensity distribution (LID) of light sources in the far field. The advantage of this system is the high-resolution acquisition of a large angular range with one image. For the uncertainty budget, the mathematical description of the system can be divided into photometric and geometric contributions. In the following, we will present a Monte-Carlo approach to analyse the geometric contributions which are the uncertainty of measurement direction and measurement distance. Therefore, we set up a geometric system description based on kinematic transformations that describes the connection between detector and light source position. To consider all relevant input quantities we simulate the adjustment and measurement process. Finally, an analysis of the geometric input parameters is shown.

Спектральные характеристики и перенос энергии Ce-=SUP=-3+-=/SUP=-->Tb-=SUP=-3+-=/SUP=-->Eu-=SUP=-3+-=/SUP=- в соединении LuBO-=SUB=-3-=/SUB=-(Ce, Tb, Eu)

The structure, IR, luminescence, and luminescence excitation spectra of Ce3+, Tb3+, and Eu3+ ions in Lu1−2xCexEuхBO3 and Lu0.91−2xCexTb0.09EuхBO3 solid solutions were studied. The minimum "threshold" distance between Ce3+ and Eu3+ ions was estimated, at which there is no charge transfer between these ions, leading to the quenching of Ce3+ and Eu3+ luminescence. It is shown that in Lu0.91−2xCexTb0.09EuхBO3 compounds, the range of Ce and Eu concentrations of 0.2 – 0.25 at. % is optimal for obtaining the maximum luminous intensity of this compound.

Calibration of a modular trap detector system towards a new realisation of the luminous intensity unit

A modular photometric trap detector system has recently been developed at Physikalisch-Technische Bundesanstalt (PTB). All parts of the detector are now completely calibrated. The new planned traceability chain for the realisation of luminous intensity unit can therefore be established for the first time. This contribution shows the results of the individual calibration steps including the associated measurement uncertainties and correlations. A major part of the calibrations along the traceability chain is done at the upgraded measurement setup TULIP (TUnable Lasers In Photometry). The improvements of the TULIP setup are presented and the effects on the measurement uncertainty are shown. The result of the first complete calibration according to the new traceability chain is compared to previous calibration results both in terms of spectral irradiance responsivity and luminous responsivity. The further steps required towards implementing the new traceability chain and the possible implications are discussed.

Enhancement of Luminous Intensity Emission from Incoherent LED Light Sources within the Detection Angle of 10° Using Metalenses

In this work, we present metalenses (MLs) designed to enhance the luminous intensity of incoherent light-emitting diodes (LEDs) within the detection angles of 0° and 10°. The detection angle of 0° refers to the center of the LED. Because the light emitted from LEDs is incoherent and expressed as a surface light source, they are numerically described as a set of point sources and calculated using incoherent summation. The titanium dioxide (TiO2) and amorphous silicon (a-Si) nanohole meta-atoms are designed; however, the full 2π phase coverage is not reached. Nevertheless, because the phase modulation at the edge of the ML is important, an ML is successfully designed. The typical phase profile of the ML enhances the luminous intensity at the center, and the phase profile is modified to increase the luminous intensity in the target detection angle region. Far field simulations are conducted to calculate the luminous intensity after 25 m of propagation. We demonstrate an enhancement of the luminous intensity at the center by 8551% and 2115% using TiO2 and a-Si MLs, respectively. Meanwhile, the TiO2 and a-Si MLs with the modified phase profiles enhance the luminous intensity within the detection angle of 10° by 263% and 30%, respectively.

Low-perchlorate blue-flame pyrotechnic compositions

An ammonium perchlorate (AP) and copper(II) benzoate pyrotechnic blue-flame composition was gradually “diluted” by adding an experimental perchlorate-free blue-flame composition based on aminoguanidinium nitrate (AGN), malachite, PVC powder and shellac resin. Flame’s luminous intensity and specific luminous intensity were recorded and analyzed. A copper-aminoguanidinium (CuAG) complex was also synthesized and tested as an energetic additive in perchlorate-free blue-flame composition. Green-flame color was observed when testing chlorine-free energetic compositions with CuAG.

GAGG:Cr3+ Phosphors for Far-Infrared Light Emitting Diodes

Recently, Far-infrared Light Emitting Diodes have attracted considerable interest in the research field worldwide. Emerging light therapy requires effective red/far-infrared light resources in clinical and plant photomorphogenesis to target or promote the interaction of light with living organisms. Here, Gd3Al4GaO12:Cr3+ (hereinafter referred to as: GAGG:Cr3+) phosphor was synthesized by high-temperature solid-phase method, and the crystal structure, morphology, and luminescence properties of this series of phosphor samples were studied. Through X-ray powder diffraction to obtain pure phase GAGG:Cr3+ series phosphor. Under the excitation of 420nm blue light, a broad band emission from 640 to 850nm is obtained, which is the result of the transition of Cr3+ 4T2→4A2 level. A sharp emission peak at 693nm is the R line belonging to Cr3+ in Gd3Al4GaO12 garnet. R line is assigned to the spin-forbidden 2E→4A2 transitions of Cr3+ ions that occupy the ideal octahedral sites. As the Cr3+ doping concentration increases, the luminous intensity of the sample increases first and then decreases. When the doping concentration of Cr3+ is 0.1mol phosphor,the luminous intensity is strongest at one single broad peak at about 712nm. At 440k, the R sharp line (693nm) and broad band (712nm) emission intensity maintained 78.6% and 71.8% , compared to room temperature intensity, respectively. The change of fluorescence lifetime at different temperatures gives the mechanism of fluorescence change with temperature. The current exploration will pave a promising way to engineer GAGG:Cr3+ activated optoelectronic devices for all kinds of photobiological applications.

Luminescence Properties and Energy Transfer of Tm3+-Eu3+ double Doped LiLaSiO4 Phosphors

A series of LiLaSiO4:yTm3+, zEu3+ phosphors were prepared by high temperature solid-phase reaction. The microstructure, luminescence performance and quantum yield of the phosphors are characterized by XRD, SEM and fluorescence spectrometer. When the monitoring wavelength is 360 nm, LiLaSiO4:yTm3+ phosphors showed a sharp emission peak at 460 nm, corresponding to the 7F0→5D2 energy level transition, and the concentration quenching point of Tm3+ ions was y = 0.015. When the monitoring wavelength is 360 nm, LiLaSiO4:yTm3+, zEu3+ phosphors have emission peaks of Tm3+ and Eu3+ ions at 460 and 618 nm, respectively. As the molar mass fraction of Eu3+ ions doped increases, the luminous intensity of Tm3+ ions gradually decrease, and the luminous intensity of Eu3+ ions increases first and then decreases, and the concentration quenching point of Eu3+ ions was z = 0.08. The energy transfer of Tm3+→Eu3+ ions through electric dipole- electric dipole interactions is demonstrated by the luminous intensity variation law and fluorescence lifetime. By changing the doping ratio of Eu3+ and Tb3+ ions, the full-color control of the phosphor luminescent color from blue to red can be achieved.