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Laser sources have been considered to be better light sources compared to traditional lamps or light‐emitting diodes used in projectors, which enables the projector to create images with higher color saturation, brightness, and energy efficiency. However, the speckle noise caused by the coherent nature of the laser is a major technology obstacle for laser projection, which severely affects the image quality. To suppress laser speckle, a TiO2‐sapphire composite (TSC) with rough and high reflectivity surface and high thermal conductivity substrate is designed, which reduces the laser speckle by creating spatial diversity. Moreover, combined with a micro motor, the design and fabrication of the TSC rotating wheel are realized, which further reduces the laser speckle by creating time diversity. The experimental results show that the laser speckle contrast can be reduced from 9.0% to 2.2% when placing the TSC rotating wheel in the light path, which is below the speckle perception limit of the human eye (<4%). This new type of laser speckle suppression device is simple to use, low in cost, high in energy utilization, high in thermal conductivity, easy to mass production, and has great application potential in high‐power laser projection. [ABSTRACT FROM AUTHOR]

Elpasolite crystals are very important materials, both from the applied and fundamental points of view. Those elpasolites, which contain rare earth ions with a high atomic number Z, are very much suitable for the low‐cost high‐performance gamma‐ray detection, applications in medicine, food industry, nuclear energy production, processing, and detection of nuclear proliferation. The thermal and structural stabilities are important parameters required for detecting applications, because the performance conditions for such devices are usually very harsh. Since it is widely believed that elpasolites may have even better detection properties, the lack of systematic studies on the elpasolites and thus the unavailability of reliable data on their physical properties and trends in their variation caused by chemical composition considerably hinders search for more efficient new materials. Therefore, to fill in this gap and provide with all essential information about a large number of elpasolites crystals, for the first time, the structural stability, elastic, vibrational, and electronic properties of 60 cubic elpasolite Cs2NaLnX6 (Ln = La, ..., Lu, X = F, Cl, Br, I) crystals were consistently calculated in the framework of the same computational approach based on the density functional theory (DFT). Variation of all calculated parameters (such as the lattice constants, elastic constants, Debye temperature, normal vibrational modes frequencies, Mulliken effective charges, bond populations, and band gaps) across the considered groups of crystals was analyzed and several trends, which are important for the search and preparation of new stable materials with improved performance, were identified. [ABSTRACT FROM AUTHOR]

Abstract: The electronic, structural, and optical properties of 2 red phosphors, Rb2HfF6:Mn4+ and Cs2HfF6:Mn4+, are evaluated using the first‐principles and crystal field theory methods. The calculated trigonal splitting of the Mn4+ orbital triplets perfectly matches the experimental excitation spectra. The structural and electronic properties of the mixed compound RbCsHfF6 are also studied theoretically. In the mixed compound, the inversion center symmetry around the Hf site is removed. This symmetry lowering may result in an increase in the Mn4+2E→4A2 zero phonon line (ZPL) intensity, which is very weak in the 2 end members. This finding may be of interest for increasing the phosphor luminosity. It is believed that such a mechanism of local site symmetry lowering by preparing solid solutions may be used for other systems as well, to gain ZPL intensity and perhaps to minimize thermal losses, eventually leading to improved phosphor materials. [ABSTRACT FROM AUTHOR]

Abstract: The electronic, structural, and optical properties of 2 red phosphors, Rb2HfF6:Mn4+ and Cs2HfF6:Mn4+, are evaluated using the first‐principles and crystal field theory methods. The calculated trigonal splitting of the Mn4+ orbital triplets perfectly matches the experimental excitation spectra. The structural and electronic properties of the mixed compound RbCsHfF6 are also studied theoretically. In the mixed compound, the inversion center symmetry around the Hf site is removed. This symmetry lowering may result in an increase in the Mn4+2E→4A2 zero phonon line (ZPL) intensity, which is very weak in the 2 end members. This finding may be of interest for increasing the phosphor luminosity. It is believed that such a mechanism of local site symmetry lowering by preparing solid solutions may be used for other systems as well, to gain ZPL intensity and perhaps to minimize thermal losses, eventually leading to improved phosphor materials. [ABSTRACT FROM AUTHOR]