Most of the methods developed so far represent significant advancements beyond the state of the art in the fields of optics, acoustics, and imaging.
Our work demonstrates that ultrasonic endoscopes enable light guiding in scattering phantoms with an optical thickness of 15, a 7-fold improvement in light focusing compared to external lenses. The method is fast, only limited by the speed of sound within the medium, and the required pressure values render it de facto non-invasive. This is a first step toward extending light-focusing depth inside biological tissue.
We have also developed an all-optics system to characterize 3D pressure fields, retrieving information from a 100x100x100 point volume with micrometer resolution in just 10 seconds, compared to the 56 hours required by a needle-hydrophone. Such a drastic reduction in acquisition time represents a significant advancement toward the rapid characterization of pressure fields.
Additionally, we exploited the acousto-optic effect to enhance speed and flexibility in metrology and microscopy, offering real-time characterization of rapidly moving samples with previously unattainable precision and wavelength ranges.
So far, all our results have been demonstrated on test targets or phantom samples. We plan to start working on biological tissue, specifically colorectal organoids, in the near future. By combining simulation with experiments, we also plan to continuously improve the guiding effects of ultrasonic endoscopes. Additionally, we plan to combine ultrasonic endoscopes with state-of-the-art imaging, spectroscopy, and phototherapy techniques, including two-photon microscopy, photoacoustic microscopy, and fluorescence correlation spectroscopy, to further extend their operational depth.
At the end of the project, we expect to develop a novel non-invasive, and rapid approach for focusing light at a spatial resolution and depth not currently possible.
