Monte Carlo Simulation And Experimental Studies Of Optical Properties Of Luminescent Glasses

In recent years, white light-emitting diodes (W-LEDs) have attracted greatattention in the solid state lighting area and show high potential for the replacement ofconventional light sources such as candescent and fluorescent lamps in the future. Incomparison with conventional light sources, W-LEDs possess the advantages of theirlong life-time, low consumption and much compact packages and so on. For the mostwidely used W-LEDs which are combined by LED chip and phosphor, the phosphorsare applied as powders that are embedded in organic resin, these LEDs have poorheat-resistance. Compared with the conventional phosphors, luminescent glasses arepromising phosphor candidates for W-LEDs due to their specific advantages such asexcellent heat-resistance, easy formation of any shape, low production cost, simplermanufacture procedure and environment protection. If the luminescent glass and LEDexcitation chip combined into the LED device, luminescent glasses play roles both inemitting light and adjusting light distribution, so the optical properties of luminescentglasses need to be further study.This paper mainly studied the optical parameters how to impact the external quantumefficiency and the radiation pattern of luminescent glass, and the following work wasdone:â‘ The optical processes of photons transportation and changing in luminescentglass were analyzed. A simplified model of violet LED combined with luminescentglass was proposed, and then the optical processes were simulated by Monte Carlomethod. The calculation methods of external quantum efficiency and radiation patternof luminescent glass were obtained.â‘¡According to the definition of external quantum efficiency, the externalquantum efficiency of Tb doped luminescent glasses with different concentrations wascalculated by using Monte Carlo simulation. The simulation results of fluorescenceexternal quantum efficiency for luminescent glasses were proved by experiment. Therelationship between external quantum efficiency and refractive indices, the absorptioncoefficient of glass matrix and luminescent glass, the concentration of the rare earth ions,internal quantum efficiency has been research. The results show that the glass matrixabsorption for excitation light is the most important factor for the external quantumefficiency of luminescent glass. For preparation high external quantum efficiency of luminescent glass, the high transmittance of glass matrix should be selected; the phononenergy should be reduced by adjusting glass matrix components; finally changing thesurface roughness and shape of luminescent and improving the concentration of rareearth ions.â‘¢The radiation patterns of violet LED combined with Eu3+doped luminescentglass were tested and simulated, then the results of simulation and experiment wereanalyzed. At last, the radiation patterns of different shape and size luminescent glasseswere simulated and analyzed. The results shows: for the LED chip combined withluminescent glass, the shape of luminescent glass change the spatial light intensitydistribution, the size of luminescent glass change intensity value of direction.