纳米结构环境中扩散激发的时变磷光衰减
Diffusion-inspired time-varying phosphorescent decay in nanostructured environment
摘要：
结构化环境通过修改局部电磁态密度控制光-物质相互作用过程的动力学。在典型的情况下，其中涉及纳秒级的荧光过程，在相互作用过程中的环境的机械构象变化可以安全地忽略。然而，缓慢衰减的磷光络合物（例如镧系元素）可以通过近场相互作用有效地感测微米和毫秒尺度的运动。因此，寿命统计可以继承有关纳米尺度的机械运动的信息。在这里，我们研究磷光染料的光-物质相互作用动力学，在等离子体纳米天线附近扩散。通过修正的扩散方程，考虑了随时间变化的Purcell增强和分子随机运动之间的相互作用，并分析了集体衰变现象。流体性质，如局部温度和扩散系数映射到磷光寿命分布提取的逆拉普拉斯变换的帮助。我们提出了一个相当简单的光子平台，实现了非接触式全光学测温和扩散测量，并为大量可能的应用铺平了道路。其中，所提出的分析可用于详细研究芯片实验室设备中的纳米流体过程，这是非常困难的，甚至不可能用其他光学方法进行分析。
英文摘要：
Structured environment controls dynamics of light-matter interaction processes via modified local density of electromagnetic states. In typical scenarios, where nanosecond-scale fluorescent processes are involved, mechanical conformational changes of the environment during the interaction processes can be safely neglected. However, slow decaying phosphorescent complexes (e.g. lanthanides) can efficiently sense micro- and millisecond scale motion via near-field interactions. As the result, lifetime statistics can inherit information about nano-scale mechanical motion. Here we study light-matter interaction dynamics of phosphorescent dyes, diffusing in a proximity of a plasmonic nanoantenna. The interplay between the time-varying Purcell enhancement and stochastic motion of molecules is considered via a modified diffusion equation, and collective decay phenomena is analysed. Fluid properties, such as local temperature and diffusion coefficient are mapped on phosphorescent lifetime distribution extracted with the help of inverse Laplace transform. We present rather simple photonic platform enabling contactless all-optical thermometry and diffusion measurement and paving a way for a plethora of possible applications. Among them, the proposed analysis can be used for detailed studies of nanofluidic processes in lab-on-a-chip devices, which are extremely hard or even impossible to analyse with other optical methods.
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