In nanoparticle-assisted photothermal microscopy, absorption of radiation by a nanoparticle is followed by nonradiative relaxation, which leads to changes in the surrounding medium temperature, pressure, and density. Under harmonically modulated irradiation, the finite heat diffusion rate causes a phase delay between the thermal oscillation at a location in the medium relative to that at the nanoparticle surface. The phase delay averaged over the probe laser volume can be measured concomitantly with the amplitude of detected probe power modulation. In this study we show that, in conjunction with the more widespread measurement of the modulation amplitude, the photothermal phase can provide a complementary, sensitive probe of thermally induced changes in the local medium properties. As proof of principle, we study a widely used, technologically important polymer resist: polydimethylsiloxane (PDMS). In addition we show how, with the help of simulations, it is possible to extract from phase/amplitude data the temperature-dependent properties of the photoannealed medium.

中文翻译：

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时谐光热显微镜研究纳米颗粒辅助的聚二甲基硅氧烷光退火

在纳米粒子辅助的光热显微镜中，纳米粒子吸收辐射后会发生非辐射弛豫，从而导致周围介质温度，压力和密度发生变化。在谐波调制辐射下，有限的热扩散速率导致介质中某个位置的热振荡相对于纳米颗粒表面的热振荡之间的相位延迟。可以与检测到的探针功率调制幅度同时测量在探针激光体积上平均的相位延迟。在这项研究中，我们表明，与更广泛的调制幅度测量相结合，光热相可以为局部介质属性中的热诱导变化提供互补的敏感探针。作为原理证明，我们研究了广泛使用的 技术上重要的聚合物抗蚀剂：聚二甲基硅氧烷（PDMS）。此外，我们展示了如何借助模拟从相位/振幅数据中提取光退火介质的温度相关特性。