Résumé: © 2020 Elsevier GmbH The gold nanocrescent (NC) particles possess a strong plasmon resonance which gives them a strong scattering cross section. They can thus be easily tracked using dark-field microscopy. In this study, we improved the optical configuration setup of dark-field video microscope to simultaneously measure the translational and rotational local temperatures within a glycerol medium. The translational and rotational local temperatures have been measured on the same single gold nanocrescent particle when it was excited by green and red laser. The rotational local temperature was measured by the technique of rotational scattering correlation spectroscopy (RSCS) and the translational local temperature was measured by tracking a single nanoparticle technique through the determination of translational diffusion coefficient under Brownian motion. The result showed that the translational local temperature was significant lower than the rotational local temperature for the same single gold nanocrescent. Remarkablely, we can affirm that the heterogeneity of the optical environment leads to the difference between these two temperatures. The obtained results have a great potential to probe the local nanorheology of a material.

Résumé: Focusing waves inside inhomogeneous media is a fundamental problem for imaging. Spatial variations of wave velocity can strongly distort propagating wave fronts and degrade image quality. Adaptive focusing can compensate for such aberration but is only effective over a restricted field of view. Here, we introduce a full-field approach to wave imaging based on the concept of the distortion matrix. This operator essentially connects any focal point inside the medium with the distortion that a wave front, emitted from that point, experiences due to heterogeneities. A time-reversal analysis of the distortion matrix enables the estimation of the transmission matrix that links each sensor and image voxel. Phase aberrations can then be unscrambled for any point, providing a full-field image of the medium with diffraction-limited resolution. Importantly, this process is particularly efficient in random scattering media, where traditional approaches such as adaptive focusing fail. Here, we first present an experimental proof of concept on a tissue-mimicking phantom and then, apply the method to in vivo imaging of human soft tissues. While introduced here in the context of acoustics, this approach can also be extended to optical microscopy, radar, or seismic imaging.