Huili Tang

Study on the effect of heat-annealing and irradiation on spectroscopic properties of Bi:α-BaB 2 O 4 single crystal

The absorption, excitation, and ultrabroadband near-infrared luminescence spectra of Bismuth were investigated in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4)(alpha-BBO) single crystals, respectively. Energy-level diagrams of the near-infrared luminescent centers were fixed. The electronic transition energies of near-infrared active centers are basically consistent with the multiplets of free Bi(+) ions. The minor difference of the energy-level diagrams of Bi(+) ions in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4) crystals can be ascribed to the difference of the local lattice environments. The involved physical and chemical processes were discussed. The effect of Ar-, air-annealing and electron-irradiation on Bi:alpha-BaB(2)O(4) crystal were also investigated.

Near-infrared photoluminescence spectra in Bi-doped CsI crystal: evidence for Bi-valence conversions and Bi ion aggregation

Bi-doped CsI crystals exhibited near-infrared ultra-broadband photoluminescence around 1216 nm and 1560 nm, depending on the bismuth doping levels, which were ascribed to Bi+ and Bi2+ centers, respectively. The crystal chemistry of the Bi3+ to Bi+ reduction and Bi2+ dimer formation in CsI lattice were investigated. Thermal treatments including annealing and quenching were carried out to study the thermal behaviors of the two emission bands. The evolution of absorption and emission spectra of Bi:CsI crystals indicating the Bi-aggregation and valence conversions under thermal activation. The process of Bi aggregation was observed to be a second-order reaction with activation energy of 0.33 eV. Bi2+ was identified as the origin of the 1560 nm emission band with ESR spectra. A simple lattice structure diagram was developed to illustrate the physical processes in Bi:CsI crystals induced by thermal activation.

Broadband photoluminescence of Bi2O3–GeO2 binary systems: glass, glass-ceramics and crystals

Ultra-broadband emission covering 1000?1800 and 1800?3020?nm of Bi2O3?GeO2 binary system materials, from glass to glass-ceramics to crystals, is presented in this paper. This is the first time, to our best knowledge, that broadband photoluminescence of BGO crystals (including Bi4Ge3O12 and Bi12GeO20) in the range of 1800?3020?nm has been realized. HRTEM, XPS and XANES have been used to investigate the effects of the valence states and the structure environment of bismuth on the emission properties of Bi2O3?GeO2 binary system materials. Bi2+ and Bi+ are proposed as the emission centers of the photoluminescence peaks at 1060 and 1300?nm, respectively. The broadband emission from 1800 to 3020?nm originates from bismuth clusters. Bi2O3?GeO2 binary system materials could be promising laser materials in the field of full-band optical fiber communication amplifiers, ultra-fast lasers and diode pumped solid state lasers, due to their broadband emission spectra and their feasibility of synthesis and drawing into fibers.

Near-infrared to mid-infrared photoluminescence of Bi 2 O 3 -GeO 2 binary glasses

Near-infrared and mid-infrared (MIR) ultrabroad emission bands were observed in as-grown and annealed Bi(2)O(3)-GeO(2) binary glasses, in the wavelength ranges of 1000-1800 nm and 1800-3020 nm, respectively. The MIR emission band could appear through high doping ratio of Bi(2)O(3) or annealing process in air atmosphere. The structure of these glasses, the transformation of emission centers, and the effect of Al ions doping have been discussed, with the conclusion that the Bi(2)O(3)-GeO(2) binary glasses could be a promising laser material.

Growth and Development of Sapphire Crystal for LED Applications

LEDs (Light emitting diodes) are considered as the most promising green lighting sources in 21st Century for the advantages in high brightness, long lifetime (more than 50,000 hours), low energy consumption, short corresponding time, good shock resistance, non-toxic, recy‐ clable, safety. LEDs have already been extensively used in outdoor displays, traffic lights, high-performance back light units in liquid-crystal displays, general lighting. Strategies Un‐ limited Company predicted that the compound annual growth rate (CAGR) of the LED mar‐ ket would increase to 30.6%, up to

Influence of thermal treatment on the near-infrared broadband luminescence of Bi:CsI crystals

20.2 billion in 2014. It is obvious that incandescent bulbs and fluorescent lamps will be replaced by LEDs, which could alleviate the increasingly seri‐ ous global energy crisis. Therefore, the development of semiconductor lighting industry is of great significance. Many countries have already launched National Semiconductor Light‐ ing Plan, investing heavily in researching and developing the LEDs industry. In 1998, Japan made a “Light for the 21st Century” plan with the budget of 6 billion yen. In July 2000, Eu‐ ropean Union implemented “Rainbow project bring color to LEDs” plan, setting up ECCR and promoting the application of white light LED through the EU BRITE/ EURAM-3 pro‐ gram. U.S. Department of Energy established “National research program on semiconductor lighting” plan. It is expected that in 2025, the use of solid state lighting will reduce half of the lighting electricity consumption and save

The optically stimulated luminescence of carbon doped Y3Al5O12 (YAG) crystal

35 billion per year. In June 2003, the Chinese Ministry of Science and Technology launched an “National Semiconductor Lighting Project” in support of the “863” Project. In 2009, ministry of Science and Technology started “Ten thousand LED lights in ten cities” semiconductor lighting demonstration program. It is ex‐ pected that in 2015, semiconductor lighting will occupy 30% of the domestic general lighting market.

Crystal growth, spectroscopic characteristics, and Judd-Ofelt analysis of Dy:Lu2O3 for yellow laser

Near-infrared (NIR) emitting active centers can exist abundant in Bi:CsI crystal. In addition, Bi:CsI have the simplest crystal structure, body-centered cubic (BCC). In this paper, annealing and quenching treatments were carried out in detail to identify the nature of NIR emitting active centers in Bi:CsI crystals. The changes of absorption and emission spectra with increasing the thermal treatment temperature indicated that the two NIR emission bands at 1210 nm and 1580 nm were related to Bi+ and Bi2+, respectively. Besides, the assignments of absorption bands and the thermal behaviors of Bi3+, Bi2+, Bi+ and Bi2+ were discussed as well.

A Co2+-doped alumina-rich Mg0.4Al2.4O4 spinel crystal as saturable absorber for a LD pumped Er: glass microchip laser at 1535 nm

Carbon doped YAG (YAG : C) crystal is designed and grown by the temperature gradient technique, and the optical and optically stimulated luminescence (OSL) properties of the as-grown crystal are investigated. High concentration F+-centres with an emission at 400 nm are produced in the YAG crystal by the introduction of carbon. The as-grown YAG : C shows high OSL sensitivity and excellent OSL response thermal stability up to 573 K. In the wide dose range from 0.1 to 50 Gy, the OSL response shows excellent linearity, and saturation is found at about 200 Gy. Almost no light-induced fading is observed in the YAG : C crystal when exposed in the dark.

Growth method of rectangular specially-shaped sapphire crystal

Dy:Lu2O3 was grown by the float-zone (Fz) method. According to the absorption spectrum, the Judd–Ofelt (JO) parameters Ω 2, Ω 4, and Ω 6 were calculated to be 4.86 × 10−20 cm2, 2.02 × 10−20 cm2, and 1.76 × 10−20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2→6H13/2 transition was calculated to be 0.53 × 10−20 cm2. The yellow (4F9/2→6H13/2 transition) to blue (4F9/2→6H15/2 transition) intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy:Lu2O3 is a promising material for use in yellow lasers.