Phonon probe microscopy: towards acoustically-resolved Brillouin spectroscopy

以超光学分辨率成像活细胞是显微镜学的一个重大突破，它使细胞生物学的许多领域得以发现。然而，现有技术存在局限性。特别是，基于荧光显微镜的超分辨率需要使用对细胞有毒且只能短时间使用的染料。电子显微镜与活细胞完全不相容，原子力显微镜是侵入性的，仅限于表面附近。此外，用任何这些技术表征材料性能仍然极具挑战性。直到今天，短波辐射造成的损害对生物成像施加了严格的限制。这些限制不适用于声子，声子携带的能量比电磁辐射少几个数量级。这为无标签、超光学分辨率显微镜提供了一条令人兴奋的途径。此外，声子成像提供了与标本弹性有关的信息。这些方面的结合为生命科学和医疗保健应用提供了新的可能性。在这个项目中，我提出了一种利用声子声学实现超光学分辨率的新方法。通过使用激光产生的声子场，可以制造出足够小的透镜，以产生亚光学波长的紧密聚焦声子束。这些场将通过布里渊散射来检测，以在安全的光学波长下提供基于弹性的对比：声子探针显微镜概念的证明。

Imaging living cells at super-optical resolution is a major breakthrough in microscopy which has enabled discovery in numerous areas of cell biology. However, the existing technologies present limitations. In particular, super-resolution based in fluorescence microscopy requires the use of dyes that are toxic to cells and can only be used for short periods. Electron microscopy is completely incompatible with live cells and atomic force microscopy is invasive and limited to the vicinity of the surface. Moreover, the characterisation of material properties with any of these techniques remains extremely challenging. To this day, the damage caused by short-wavelength radiation enforces strong restrictions to biological imaging. These limitations do not apply to phonons, which carry orders of magnitude less energy than electromagnetic radiation. This offers an exciting path for label-free, super-optical resolution microscopy. Moreover, imaging with phonons provides information related to the elasticity of the specimens. The combination of these aspects offers new possibilities in life sciences and healthcare applications. In this project, I propose a new way of achieving super-optical resolution by means of phonon acoustics. By using laser-generated phonon fields, it is possible to produce lenses small enough to produce tightly focused phonon beams with sub-optical wavelengths. The fields are to be detected by Brillouin scattering to provide elasticity-based contrast at safe optical wavelengths: proof of concept of the phonon-probe microscope.