Luminescence of Erbium Doped Telluride Glass Enhanced by Surface Plasmon of Metallic Silver Nanoparticles
CHEN Xiao-bo1, LI Song1, ZHAO Guo-ying2, LONG Jiang-mi1, WANG Shui-feng1, ZHENG Dong1, WU Zheng-long1, MENG Shao-hua2, GUO Jing-hua1, XU Ling-zhi2, YU Chun-lei3, HU Li-li3
1. Applied Optics Beijing Area Major Laboratory and Physics Department, Beijing Normal University, Beijing 100875, China
2. School of Materials Science and Technology, Shanghai Institute of Technology, Shanghai 200235, China
3. Shanghai Institute of the Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Abstract：Interesting optical properties of metal surface plasmon, especially the behavior on luminescence enhancement field, have become a hot research topic globally. The surface plasmon is just a kind of collective oscillation made of free electron and light electromagnetic fields because their resonant frequencies are similar when they are interacting with each other. In present paper, the erbium luminescence resonant enhanced by surface plasmon of Ag nanoparticles (NPs) in telluride glass is studied. The absorption, excitation, luminescence spectra, and lifetime are measured. First, we select the 365.5 and 379.0 nm excitation peaks as excitation wavelength to measure the visible luminescence spectra in the wave range of 385～780 nm. We find 4 luminescence peaks positioned at 408.0, 525.0, 546.0, and 658.5 nm. They are, respectively, the fluorescence transitions of 2H9/2→4I15/2, 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 of Er3+ ions. It is easy to calculate the peak intensities of the above 4 visible luminescence of (A) Er3+(0.5%)Ag(0.2%): Telluride glass with the average diameter of 80 nm for Ag NPs are about 1.44～2.52 times larger than that of the (C) Er3+(0.5%): Telluride glass. Moreover, the peak intensities of the above 4 visible luminescence spectra of (B) Er3+(0.5%)Ag(0.2%): Telluride glass with the average diameter of 50 nm for Ag NPs are about 1.08～1.55 times larger than that of the sample (C). Then, we select the 365.5 and 379.0 nm excitation peaks as excitation wavelength to measure the near infrared luminescence spectra in the wave range of 928～1 680 nm. It is found that near infrared luminescence peaks are positioned at 979.0 and 1 530.0 nm. They are, respectively, the fluorescence transitions of 4I11/2→4I15/2 and4I13/2→4I15/2 of Er3+ ions. The peak intensities of the above 2 near infrared luminescence spectra of sample (A) are about 1.43～2.14 times larger than that of the sample (C). Similarly, the peak intensities of the above 2 near infrared luminescence spectra of sample (B) are about 1.28～1.82 times larger than that of the sample (C). Therefore, the largest enhancement is about 2.52 times larger. From the experiments of fluorescence lifetime dynamics, we find that the 550 nm fluorescence lifetime of sample (A) is about τA(550)=43.5 μs, that of sample (B) is about τB(550)=43.2 μs, and that of sample (C) is about τC(550)=48.6 μs. The experimental results illustrate that τA≈τB＜τC. This means that the luminescence enhancement of sample (B) relative to sample (C) results from the spontaneous radiation enhancement effect. However, this also means that the luminescence enhancement of sample (A) relative to sample (B) results from the Size r effect, in which the increased of the scattering cross section Cs is much larger than that of the absorption cross section Ca when r is enlarged, because the scattering cross-section Cs are proportional positive ratio to r6 and the absorption cross-section Ca are proportional positive ratio to r3. As we know that the scattering cross-section Cs is the reason for the increase of fluorescence, meanwhile the absorption cross-section Ca is the reason for the decease of fluorescence. When r is increase, scattering cross-section Cs is the main part. When luminescent material couples with the metallic surface Plasmon, the energy is transferred quickly to metallic surface Plasmon, and then scattered to the far field. It’s beneficial for the enhancement of fluorescence. As a comprehensive result, the fluorescence is enhanced when r is enlarged. It has excellent application prospects in the optogalvanic electricity generation of solar cell and biophysical application other as well as fields.
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