Radiation Pressure Cooling With Localized Surface Plasmon

我们从理论和实验上研究了金属纳米带隙结构中局域表面等离子体激元(LSP)产生的辐射压力，分析了热运动下作用在纳米粒子和分子上的光学力的强度和空间分布。我们发现，在纳米带隙内LSP场的纳米尺度空间分布呈现出复杂的精细结构，而不是单峰。纳米粒子是由偶极、四极和高阶多极等离激元相互干扰而形成的。此外，我们还开发了定量分析纳米粒子辐射压力的测量系统。实验结果表明，与传统的远场捕获相比，其作用力提高了3个数量级。我们还成功地观测到了二维囚禁势，这是超分辨光学囚禁的第一个演示。

We have theoretically and experimentally investigated radiation pressure induced by localized surface plasmon (LSP) of metal nano-gap structures, and analyzed the strength and spatial distribution of the optical force exerted on nanometer-sized particles and molecules under thermal motions. We showed that the nanoscale spatial profiles of the LSP fields within the nano-gap exhibit complicated fine structures, rather than single peaks. The nanopatterns are formed by interferences of dipolar, quadrupolar, and higher-order multipolar plasmonic modes. In addition, we developed the measurement system for quantitatively analyzing the radiation pressure exerted on nanoparticles. The experimental results demonstrated that the force strength is enhance by 3 order of magnitude compared to that with conventional far-filed trapping. We also succeeded in observation of two-dimensional trapping potentials, which is the first demonstration of super-resolution optical trapping.