On the actual spatial resolution of Brillouin Imaging

TL;DR

This paper investigates the true spatial resolution of Brillouin imaging, revealing that acoustic phonon mean free path significantly influences resolution, which can worsen with smaller scattering volumes in high-NA setups.

Contribution

It challenges the conventional view by showing acoustic phonon mean free path as a key factor in Brillouin imaging resolution, beyond confocal microscope parameters.

Findings

Resolution depends on acoustic phonon mean free path.

Decreasing scattering volume can worsen resolution.

High numerical aperture setups are affected by phonon scattering.

Abstract

Brillouin imaging is an emerging optical elastography technique able to generate maps of the mechanical properties at microscale, with great potential in biophysical and biomedical fields. A key parameter is its spatial resolution, which is usually identified with that of the confocal microscope coupled to the Brillouin interferometer. Conversely, here we demonstrate that the mean free path of acoustic phonons plays a major role in defining the resolution, especially for high numerical aperture confocal setups. Surprisingly, the resolution of elastography maps may even deteriorate when decreasing the scattering volume.