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Complex logic systems using external excitation sources (1550 nm and 1064 nm lasers) as stimulus inputs and upconversion (UC) emission intensities as the optical outputs signals have been developed by taking advantage of the unique two-wavelength excitation effects. The Er3+ doped β-NaYF4 material that can achieve the emission enhancement via simultaneous dual-wavelength pumping at 1550 and 1064 nm due to the matching energy level. Elementary logic operations (OR, AND, and YES) and integrative logic operations are implemented by observing the change in two visible fluorescence emission bands (green and red) under the near-infrared excitation input conditions. The multiple outputs in our system can generate different logic operations under the same input conditions, which could increase the information content in the logic library and further improve the information processing capability. This logic system that takes infrared excitation as input and visible light as output has broad application prospects in the fields of anti-counterfeiting and information encryption. The results not only provide a deep understanding of the dual-wavelength excitation UC luminescence mechanism, but also offer a useful enlightenment for the development of novel micro/nanostructured materials for photonic devices. [ABSTRACT FROM AUTHOR]

The processes of hole localization in double-doped PbWO4 : Mo,La and PbWO4 : Mo,Y single crystals are studied by continuous wave and pulse electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. We show that the holes created by UV irradiation are preferably trapped at the oxygen lattice ions in the vicinity of perturbing defects such as lead vacancies, impurity ions (La, Y, Mo), and other lattice imperfections forming mainly two types of O- centres. The hyperfine structures of their spectra suggest that in the first centre (OI), a hole is trapped near the YPb-VPb and LaPb-VPb pairs (VPb denotes the lead ion vacancy). In the second centre (OII), a hole is probably localized within a [WO4-MoO4]3- complex defect. The recombination of thermally released holes with the electrons stored at different traps, including the oxygen-vacancy related Pb+-WO3 and (MoO4)3- centres, is systematically studied by TSL. The thermal stability parameters are evaluated by ESR and TSL techniques for different O--type defects. [ABSTRACT FROM AUTHOR]

(Ca1-xEux)3Al2O6, a red light-emitting phosphor with the excitation of purple-blue light, was prepared by traditional solid reaction method with reducing atmosphere at 1350°C for 4 h in a tube furnace. CaEuAlO4 emerged as an impurity phase when the content of Eu, x, in (Ca1-xEux)3Al2O6 exceeds 0.03. Furthermore, the content of CaEuAlO4 rises with Eu concentration. A strong excitation band centering at 467 nm and a broad emission band centering at 650 nm have been discovered in this phosphor, making it possible to manufacture a bargain price white light LEDs with high CRI. [ABSTRACT FROM AUTHOR]

Green-emitting rod-type LaPO4:Ce,Tb nanophosphors were produced by a simple, low-temperature hydrothermal route and these as-synthesized nanophosphors were subsequently annealed at 1000°C. The crystallographic structures and emission properties of the as-synthesized and annealed nanophosphors were compared. After preparing the nanophosphor dispersions, highly transparent nanophosphor layers with visible transmittance values of 92.8-98.5% at 550 nm were spin-deposited on glass substrate. Mini-sized transparent green-emitting plasma display panels (PDPs) were fabricated by combining LaPO4:Ce,Tb nanophosphor layer/glass substrate as a rear plate with a front plate used in a conventional PDP. Luminance properties of two transparent test panels using as-synthesized versus 1000°C-annealed nanophosphors were characterized and compared. [ABSTRACT FROM AUTHOR]

The dominant powder scintillator in most medical imaging modalities for decades has been Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Apart from Gd2O2S:Tb, there are alternative powder phosphor scintillators such as Lu2SiO5:Ce and Gd2O2S:Eu that have been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital mammography detectors such as CCDs. Lu2SiO5:Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purposes of the present study, two scintillating screens, one from Lu2SiO2:Ce and the other from Gd2O2S:Eu powders, were prepared using the method of sedimentation. The screen coating thicknesses were 25.0 and 33.1 mg cm-2 respectively. The screens were investigated by evaluating the following parameters: the output signal, the modulation transfer function, the noise equivalent passband, the informational efficiency, the quantum detection efficiency and the zero-frequency detective quantum efficiency. Furthermore, the spectral compatibility of those materials with various optical detectors was determined. Results were compared to published data for the commercially employed 'Kodak Min-R film-screen system', based on a 31.7 mg cm-2 thick Gd2O2S:Tb phosphor. For Gd2O2S:Eu, MTF data were found comparable to those of Gd2O2S:Tb, while the MTF of Lu2SiO5:Ce was even higher resulting in better spatial resolution and image sharpness properties. On the other hand, Gd2O2S:Eu was found to exhibit higher output signal and zero-frequency detective quantum efficiency than Lu2SiO5:Ce. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) properties of Ba3MgSi2O8:Eu2+ (BMS-E) blue phosphor and Ba3MgSi2O8:Eu2+,Mn2+ (BMS-EM) blue- red phosphor under near-U V-light excitation were investigated. BMS-E shows efficient blue-violet emission at 437 nm under 405 nm light excitation. The sample doped with 0.05 mol/mol Eu2+ shows PL peak intensity about twice higher than a commercial BaMgAl10O17:Eu2+ (BAM) for low-pressure Hg lamps. The PL integrated intensity of BMS-E below 0.2 mol/mol of Eu content is similar to that of BAM in magnitude of thermal quenching. BMS-EM shows strong red emission under 405 nm light excitation because of the efficient energy transfer from Eu2+ to Mn2+ The sample doped with 0.10 mol/mol Eu2+ and 0.10 mol/mol Mn2+ shows luminance about 12 and 3 times larger than Y2O2S:Eu3+ and La2O2S:Eu3+, respectively. Moreover, the PL integrated intensity of the BMS-EM shows less thermal quenching than that of La2O,S:Eu3+ and (Y,Gd)3(Al,Ga)5O12:Ce3+ (YAG:Ce3+). These results indicate that BMS-E and BMS-EM are promising phosphors for white light-emitting diodes (LEDs) fabricated with near-UV LEDs. [ABSTRACT FROM AUTHOR]

The red phosphor systems containing Ca1-x-yEuxMy as well as Ca1-1.5x-yEuxMy(WO4)1-z(MoO4)z (x = 0.24, y = 0.06, z = 0-1, M = Mg, Zn), were synthesized through solid-state reactions at high temperature, and their luminescent properties were reported. All of the phosphors were effectively excited by near-UV 395 nm light, and showed superior red emissions around 616 nm to the commercial red phosphor Y2O2S:Eu3+. Both the emission and excitation intensity were found to increase with increasing Mo content (z value), and reached a maximum when z = I. In particular, the Ca1-1.5x-yEuxMy(WO4)1-z(MoO4)z phosphor system, in which the charge was efficiently compensated via two Eu3+ substituting for three Ca2+ ions, exhibited enhanced red-light emissions as compared with that of the Ca1-1.5x-yEuxMy(WO4)1-z(MoO4)z system. The phosphors are promising candidates as red phosphors under near-UV excitation for solid-state lighting. [ABSTRACT FROM AUTHOR]

Designing a plastic scintillation detector for proton radiation therapy requires careful consideration. Most of the plastic scintillators should not perturb a proton beam if they are sufficiently small but may exhibit some energy dependence due to the quenching effect. In this work, we studied the factors that would affect the performance of such scintillation detectors. We performed Monte Carlo simulations of proton beams with energies between 50 and 250 MeV to study signal amplitude, water equivalence, spatial resolution and quenching of light output. Implementation of the quenching effect in the Monte Carlo simulations was then compared with prior experimental data for validation. The signal amplitude of a plastic scintillating fiber detector was on the order of 300 photons per MeV of energy deposited in the detector, corresponding to a power of about 30 pW at a proton dose rate of 100 cGy min[?]1. The signal amplitude could be increased by up to a factor of 2 with reflective coating. We also found that Cerenkov light was not a significant source of noise. Dose deposited in the plastic scintillator was within 2% of the dose deposited in a similar volume of water throughout the whole depth-dose curve for protons with energies higher than 50 MeV. A scintillation detector with a radius of 0.5 mm offers a sufficient spatial resolution for use with a proton beam of 100 MeV or more. The main disadvantage of plastic scintillators when irradiated by protons was the quenching effect, which reduced the amount of scintillation and resulted in dose underestimation by close to 30% at the Bragg peak for beams of 150 MeV or more. However, the level of quenching was nearly constant throughout the proximal half of the depth-dose curve for all proton energies considered. We therefore conclude that it is possible to construct an effective detector to overcome the problems traditionally encountered in proton dosimetry. Scintillation detectors could be used for surface or shallow measurements with a single calibration for specific beam energy. For deeper measurements, Monte Carlo simulations can be used to generate depth-dependent correction factors. [ABSTRACT FROM AUTHOR]

We investigate the emission properties of CuI film scintillators and the effect of distributed Bragg reflectors. The free-exciton emission and the donor-acceptor pair emission from the CuI thin film with the peak wavelengths of 410nm and 420nm are observed. However, for the two emission bands, the distributed Bragg reflector reflection results in different enhancements, which is interpreted by the varying transmittance with wavelength. Angledependence of emission profile is decided by the transmittance and DBR reflection, which may be useful in scintillation detection applications. [ABSTRACT FROM AUTHOR]

A series of red phosphors, NaEu(MoO4)2 doped with boron oxide, were prepared by the conventional solid-state reaction. Their excitation spectra and emission spectra were measured at room temperature. With the introduction of boron oxide, the red-emission intensity of the phosphors under 395 nm excitation are strengthened and have high color purity. In the fabricated phosphor light-emitting diodes, a bright red light can be observed by the naked eye. [ABSTRACT FROM AUTHOR]

Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can be used under stable conditions for many years even in ton scale experiments. Applications of metal loaded scintillators in neutrino experiments are reviewed and the performance as well as the prospects of different scintillator types are compared. [ABSTRACT FROM AUTHOR]

We review recent methods employed to study the excited state of rare-earth centers in various luminescent and scintillating materials. The focus is on processes that help determine localization of the excited state within the material band gap, namely photoionization and thermally stimulated ionization. Then the tunneling process between the luminescence center and the trapping state is addressed. We describe the experimental implementation of methods recently developed to study these processes. We report theoretical models helping the data interpretation. We also present application to currently investigated materials. [ABSTRACT FROM AUTHOR]

We provide a systematic comparison of the scintillation and luminescence properties, including emission mechanisms, of the highly efficient cerium-doped scintillators lutetium-(gadolinium) orthosilicates Lu2(SiO4)O (LSO), (Lu1−xGdx)2(SiO)4O(LGSO) and Gd2(SiO4)O (GSO). Determined characteristics manifest an advantage of LGSO:Ce with respect to both LSO:Ce and GSO:Ce for scintillator applications around room temperature. This is thanks to combined fast decay (faster than both limit compositions) high light yield, similar to that of LSO:Ce (twice higher than GSO:Ce) and low afterglow, similar to that of GSO:Ce (almost two orders of magnitude lower than LSO:Ce). High temperature applications do not, however, seem to be a suitable option for LGSO:Ce due to evidenced thermal ionization of both Ce1 and Ce2 centres above room temperature. [ABSTRACT FROM AUTHOR]