Random Lasing from Dye-Doped Polymer Covered Au Nanoparticles
LAN Yan-yan1, 2, LÜ Hao1, 2*, ZHAO Qiu-ling1, 2, WANG Xia1, 2*
1. College of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266061, China
2. Shandong Advanced Optoelectronic Materials and Technologies Engineering Laboratory, Qingdao 266061, China
Abstract：It’s of great significance toconduct researches of plasmonic enhanced random lasing based on metal nanoparticles which have special property and potential applications. Plasmonic enhanced random lasing has been used in surface fluorescence enhancement, optical switching device, surface plasmon laser and so on. In this paper, we propose a convenient and high-efficiency way to fabricate Au nanoparticles and study the random lasing property based on a dye-doped film covering on these particles. By changing sputtering time with 40, 80, and 120 s, different sizegold nanoparticles are prepared by sputtering and the rmal annealing on quartz substrate. The particle size increases with sputtering time enlarging. After being covered by DCJTB-doped PMMA film, low-threshold random lasing phenomenon is obtained by a 532 nm pulse beam pumping. In this study, themean particle size of Au nanoparticles, obtained at 40, 80 and 120 s sputtering time, is 230, 250 and 390 nm, respectively, and the threshold for generating random lasing under 532nm pump beam excitation is 20.5, 17.5 and 12.5 μJ·pulse-1, respectively. The larger the size and the smaller the particle spacing of Au nanoparticles, the shorter average free path of photon scattering. In that case, the light can be effectively scattered among metal particles for many times, so the scattering efficiency can be significantly improved, resulting in low threshold laser emission. When the absorption peak of Au nanoparticles is exactly matched with fluorescence peak of the dye, the fluorescence effect can be significantly enhanced. As a result, more dye molecules can be excited to generate energy level transition, and the density of photonic state is increased. During limit of damaging dye molecules by pump light, the laser can be obtained by stimulating dye molecules in multiple cycles with a slightly decrease of lasing intensity at the same level pump beam power, which is helpful for the research and development of random laser devices. The experimental results meet well with lasing theoretical analysis, which plays a significant role in clarifying random lasing emission mechanism of Au nanoparticles on photon scattering and plasmon resonance on optical absorption enhancement. Our study could provide a convenient technical method for high-efficiency and low-threshold random laser research which is expected to promote the development and application of random laser devices.
Key words：Lasing spectrum; Fluorescence enhancement; Random laser; Au nanoparticles; Surface plasmons
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