Evaluation of thermally stable phosphor screens for application in laser diode excited high brightness white light modules

A study on the preparation of thermally stable phosphor targets based on yttrium aluminum garnet doped with cerium (YAG:Ce) when excited by a high power laser diode is described. The luminous flux, chromaticity and radial spectral flux of the targets along with their thermal stability have been determined when exposed to laser powers of up to 5000 mW. This report presents successful high brightness light sources with adjustable emission properties achieved by utilizing thermally stable phosphor targets excited by high power laser diodes.Brunel University London, No. EP/K504208/

Materials Suitable for preparing Inorganic nanocasts of butterflies and other insects

Replication of 3D-structures, in particular those that have a periodic modulation of a dielectric material at optical wavelengths and below have proven very difficult to fabricate. The majority of such replication techniques are complex or use moisture sensitive precursors requiring the use of for example a glove box. Here we demonstrate how an air stable supersaturated europium-doped yttrium nitrate phosphor precursor solution has the ability to easily impregnate a structure or produce a cast yielding faithful replicas composed of Y2O:Eu3+ after a final short annealing step. New replicas of Lepidoptera (moth) wing scales using field emissionscanning electron microscopy, structures down to 10 nm have been imaged. Moreover as these replicas are made of phosphors, their luminescence in some cases may be modulated by the internal periodic modulation built into their structures. In this work we will discuss more recent results on the use of the phosphors for making nanocasts of moth wing scales and show a range of beautiful pictures to show what the method can achieve

Cathodoluminescent images and spectra of single crystals of Y2O2S:Tb3+ and Gd2O2S:Tb3+ nanometer sized phosphor crystals excited in a field emission scanning transmission electron microscope

Cathodoluminescence (CL) spectra have been collected from single nanometer-sized crystals of Y1.98Tb0.02O2S and Gd1.98Tb0.02O2S using a Gatan Vulcan cathodoluminescence imaging spectrometer. Slight variations observed in the CL spectra taken from the crystals are explained, and discussed in relation to bulk samples

Photovoltaic cells energy performance enhancement with down-converting photoluminescence phosphors

Phosphors, synthesized by the urea homo-precipitation method, were examined as ultraviolet-spectral down conversion materials for improving the light absorption and electrical characteristics of commercial single-junction silicon solar cells. The photovoltaic (PV) cells were coated with erbium and terbium doped gadolinium oxysulfide phosphors encapsulated in ethyl vinyl-acetate binder using blade screen printing technique, and the optimum concentration of phosphor in the composite resulted in the largest light conversion, and superior electrical output and energy transfer efficiency. Moreover, the results demonstrated that the composition of dispersed phosphors has a strong influence on the amount of ultraviolet-light converted and electron transition capacity of PV cells. The experimental results showed in an optimized PV cell, an enhancement of 0.54% (from 12.11% to 12.65%) in the energy conversion of a Si-based PV cell was achieved.Mr. Ben Parker of LOT-QuantumDesig

Investigating the emission characteristics of single crystal YAG when activated by high power laser beams

© The Author(s) 2016. Limitations associated with light emitting diodes (LEDs) operating under high current densities due to the efficiency droop has created a need to look for alternative light sources; here we report investigations on the potential of laser diodes (LDs) for high brightness lighting solutions. High power laser diodes require phosphor targets with certain performance criteria such as high thermal conductivity, efficiency and structural geometry. Here we examine the possibility of using single crystal YAG:Ce phosphor materials as potential targets for generation of light via laser diodes. We report on the emission properties of the crystals with different sizes and examine the effect of laser beam incident angle incident on crystal target emission

Performance of four CVD diamond radiation sensors at high temperature

Copyright © 2019 The Authors. Ionising radiation detectors based on wide band-gap materials have the potential to operate at temperatures higher than . Such detectors are important in applications such as monitoring near nuclear reactors and in deep oil and gas well borehole logging. We discuss the development of alpha particle detectors, based on CVD diamond, which operate with high charge collection efficiency and energy resolution at temperatures up to . Four nominally identical commercial, electronic grade, CVD diamonds have been coated with a thin metal conductive layer in our laboratory and then attached to ceramic PCB. We present the I–V characteristics, the charge collection efficiency and the energy resolution for alpha particles from a mixed source, for the four sensors operating at temperatures from 20 to . Monte Carlo simulations of the energy spectra and charge collection efficiency and experimental measurements of these are presented. Energy resolutions between 1.6% and 4.0% at elevated temperatures with charge collection efficiency exceeding 96% were measured. The potential for thermal neutron detection is discussed.EPSRC ref: EP/L504671/1 High temperature radiation hard detectors (HTRaD

Development of high temperature, radiation hard detectors based on diamond

© 2016 Single crystal CVD diamond has many desirable properties compared to current, well developed, detector materials; exceptional radiation, chemical and physical hardness, chemical inertness, low Z (close to human tissue, good for dosimetry), wide bandgap and an intrinsic pathway to fast neutron detection through the 12C(n,α)9Be reaction. However effective exploitation of these properties requires development of a suitable metallisation scheme to give stable contacts for high temperature applications. To best utilise available processing techniques to optimise sensor response through geometry and conversion media configurations, a reliable model is required. This must assess the performance in terms of spectral response and overall efficiency as a function of detector and converter geometry. The same is also required for proper interpretation of experimental data. Sensors have been fabricated with varying metallisation schemes indented to permit high temperature operation; Present test results indicate that viable fabrication schemes for high temperature contacts have been developed and present modelling results, supported by preliminary data from partners indicate simulations provide a useful representation of response

Laser-Activated Luminescence of BaAl2O4:Eu

© 2020 The Author(s). In this article the laser-activated (LA) luminescence of BaAl2O4 doped with 3 mol% Eu2+ and SrAl2O4 doped with 700 ppm Eu2+ is described. The LA spectrum of BaAl2O4:Eu did not show any emission from Eu2+, but rather luminescence from the Eu3+ ion. This surprising result is explained in terms of ionization of the excited Eu2+ ions (photo-ionization), while the freed electrons are trapped in an excited state of the F-centre: this is considered to be a deep trap. The temperature of the ferroelectric-paraelectric phase transition in BaAl2O4 has been determined at ≈180 °C from the Raman spectra recorded at various temperatures.PURPOSE (TP11/MFE/6/1/AA129F; EPSRC TS/G000271/1) and CONVERTED (JeS no. TS/1003053/1), PRISM (EP/N508974/1) and FAB3D programs