Development of an optical-resolution photoacoustic microscope

Abstract

High-resolution, non-invasive, deep imaging in highly dispersive media is a key challenge in modern microscopy, as it would lead to many biomedical advancements. A potential solution is to use the photoacoustic effect, which allows to retrieve optical information through acoustic waves. These waves are generated by the local temperature rise at the sample points irradiated with pulsed light and then propagate though the medium, experiencing much less dispersion than light. In this study, we present the development process of a custom-made optical-resolution photoacoustic microscope. To this end, we first characterized the used laser beam and optical system and found the beam width at the focus to be w0 ∼ 40 μm. Then, we processed and analyzed the photoacoustic signal, detected with a transducer, using the Hilbert transform. Finally, we show that images can be retrieved successfully from a sample using the designed and assembled microscope. We anticipate that the proposed OR-PAM microscope is a first step toward the use of the photoacoustic effect for deep imaging at micrometric resolution, and could be further improved and optimized by using a lower pulse energy and a higher sampling frequency