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The optical Tamm state(OTS), which exists generally at the interface between metal and a dielectric Bragg mirror, has been studied extensively in the visible and near infrared spectra. Nevertheless, OTS in the terahertz(THz) region normally receives far less attention. In this Letter, we demonstrate the physical mechanism of OTS at the interface between graphene and a dielectric Bragg mirror in the THz frequency band by applying the transfer matrix method and dispersion characteristics. Based on such mechanisms, we propose an efficient method that can precisely generate and control OTS at a desired angle and frequency. Moreover, we show that the OTS is dependent on the optical conductivity of graphene, making the graphene–dielectric-Bragg-mirror a good candidate for dynamic tunable OTS device in the THz frequency range. 相似文献
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以甘氨酸为燃烧剂,采用低温燃烧法制备了Tm3+,Ho3+共掺杂的Y2O3纳米晶粉末,通过X射线衍射和透射电子显微镜(TEM)对样品的结构、形貌和粒径进行了分析和表征.本文以785 nm LD为激发光,研究了样品的上转换发光性质,实验结果得到了峰值波长为487 nm(蓝色),548 nm(绿色),659 nm和695 nm(红色)上转换发光.经过分析表明,上述发光分别指5F3→5I8(Ho3+)+1G4→3H6(Tm3+),(5F4,5S2)→5I8(Ho3+),5F5→5I8(Ho3+)和3F3→3H6(Tm3+)跃迁.通过对上转换发光强度和激发光功率的关系研究,揭示出其均为双光子过程,并且能量传递上转换和激发态吸收是上转换发光的主要机制.由于其高效的上转换发光性能,该材料在荧光标记、三维立体显示等方面有着潜在的应用前景. 相似文献
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980 nm LD激发下稀土掺杂Gd_2Ti_2O_7粉末上转换发光 总被引:1,自引:0,他引:1
用高温固相法分别合成了Er~(3+)/Yb~(3+),Ho~(3+)/Yb~(3+),Tm~(3+)/Yb~(3+)离子共掺杂的Gd_2Ti_2O_7粉末,X射线衍射结果表明所制备的粉体为立方相烧绿石结构,TEM电镜照片显示其颗粒平均粒径为3μm.该粉末在980 nm LD激发下,分别发射出中心波长为553 nm绿色和662 nm红色(掺Er~(3+)样品)、545 nm绿色和652 nm红色(掺Ho~(3+)样品)、482 nm蓝色和653 nm红色(掺Tm~(3+)样品)的上转换荧光.上转换发光强度和激发功率的关系研究表明,能量传递和激发态吸收是上转换发光的主要机制.同时对Yb~(3+)-Er~(3+),Yb~(3+)-Tm~(3+)共掺体系的上转换发光强度"过饱和"现象进行了分析,认为是样品的被激发点的温度升高导致了荧光猝灭现象. 相似文献
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为研究影响海冰单轴压缩强度的因素,在渤海辽河口附近海域采集冰坯,加工成方柱状冰样.在试验温度分别为-3℃,-5℃,-7℃,-10℃和-15℃下,对225个冰样沿平行和垂直自然冰表面方向进行加载.研究试样温度,加载方向,应变速率和孔隙率对海冰单轴压缩强度的影响.试验结果表明:海冰单轴强度随试样温度的降低而增加;垂直方向冰样的峰值强度高于水平方向,海冰表现为各向异性.利用试验结果建立了韧性区内海冰单轴压缩强度与应变速率和孔隙率的统计关系. 相似文献
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