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Cao D.,CAS Shanghai Institute of Optics and fine Mechanics | Cao D.,University of Chinese Academy of Sciences | Zhao G.,CAS Shanghai Institute of Optics and fine Mechanics | Dong Q.,CAS Shanghai Institute of Optics and fine Mechanics | And 9 more authors.
Chinese Optics Letters

YAG:Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique (TGT). The effects of annealing on the luminescence efficiency of YAG:Ce crystal are investigated, and the optimal annealing temperature and atmosphere are obtained. The mechanism of variation behavior of the luminescence efficiency of YAG:Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed. © 2010 Chinese Optics Letters. Source

Tian C.-J.,Changchun University of Science and Technology | Tian C.-J.,Zhejiang Gemcore Technology Co. | Zhang X.-Y.,Changchun University of Science and Technology | Zou J.,Zhejiang Gemcore Technology Co. | And 2 more authors.
Faguang Xuebao/Chinese Journal of Luminescence

Using the high power light-emitting diode ( LED ) made by the method of chip-on-board ( COB ) packaging, this article compared and analyzed the temperature variation discipline on the different thermal radiators. We investigated the relationship between the different thermal equilibrium temperature and photoelectric parameter, such as luminous flux, electrical parameters, and so on. The results shown that when the LED illumination system is turned on, the temperature of the radiator rises rapidly, and keeps in a certain value after a period of time. In this process, the luminous flux, the forward voltage, power and luminous efficiency presents the downward trend. These parameters fluctuate around the equilibrium value. For high-power white light LED illumination systems, luminous flux, forward voltage and luminous efficiency keeps good linear relationship with radiator temperature, respectively. The results also showed that, with the rising of reverse saturation current, the radiator temperature rapidly rises. By linear fitting, luminous flux temperature coefficient, voltage temperature coefficient and luminous efficiency temperature coefficient were calculated. Finally, the relation formula of temperature and luminous flux was proposed. By measuring the radiator temperature, the luminous flux can be calculated. It can be used as a kind of calculation methods of luminous flux. High-power white LED lighting system should be reasonable design to improve its thermal dissipation capacity. Reducing equilibrium temperature of high-power LED-lighting system is an effective method to improve performance of the system. Source

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