粒径和浓度对YAG∶Ce荧光膜复合材料及pc-WLED发光性能的影响

采用高温压膜工艺,以YAG∶Ce黄色荧光材料和硅胶为原料制备出YAG∶Ce荧光膜复合材料,并与蓝光LED复合封装出pc-WLED.基于Mie理论、荧光光谱仪、快速光谱辐射计和光谱分布测量仪分别对不同荧光材料粒径和浓度制备的膜材料和pc-WLED的光色参数进行了计算测试,并对影响机理进行了相应分析.在相同浓度下,随着粒径减小,膜材料中激发光子平均自由程降低、散射系数升高,被吸收和转换的几率提高,引起膜材料发射强度、pc-WLED发光效率和光色均匀度均相应提高,同浓度下粒径最优值为8.7μm;在相同粒径下,膜材料发射强度、pc-WLED发光效率和光色均匀度与浓度成正比关系;基于发光效率、光色均匀度、色温和荧光材料用量等因素交叉综合评价,当浓度为4%,粒径为8.7μm时为最优参数,pc-WLED色温为5 514K,发光效率为136.8lm/W(@300mA,6.6V),光色均匀度为0.759,色坐标x=0.332 2,y=0.359 6,色点位于黑体辐射曲线附近,在不同电流下,pcWLED光通量和发光效率满足线性变化,即光通量:y=0.6816x+63.121,R2=0.995 7,发光效率:y=-0.062 8x+155.2,R2=0.991 6.该膜材料在pc-WLED中的应用是可行的,同时所获得的相关规律对于实际应用具有一定的参考作用.     

Nonlinear optical properties of an azobenzene polymer

The nonlinear optical properties of an azobenzene polymer azol2-MO were investigated by a Z-scan technique. The polymer was synthesized by assembling the liquid-crystalline polymer azol2 with methyl orange. The nonlinear refrac- tive index （1.39×10^-15 cm2/W） and the nonlinear absorption coefficient （0.11 cm/GW） of azol2-MO were determined with 532-nm picosecond laser pulses at the irradiance of 92.40 GW/cm2. When compared to the nonlinear properties of azol2 and methyl orange, azol2-MO possesses the advantages of its two constituents and shows larger nonlinear optical properties.