Dr. Kai Lou

Granick group, Center for Soft and Living Matter, Institute for Basic Science, South Korea

Abstract:Many efforts have been made to reconstruct complex tissue in 3D with fluorescence microscopy in the past decades. However, there are major impediments due to the highly scattered tissue background, which induces its degraded resolution and unavoidable shallow imaging depth. We show that without using adaptive optics, optical aberration due to refractive-index-mismatching can be eliminated by cleverly applying of the spatiotemporal focusing to the photoexcitation. Unprecedented near-diffraction-limited axial resolution in wide field imaging was successfully obtained with mouse lung tissue, with significantly deeper imaging depth, in addition to higher sample contrast. The optical physics that has long been neglected is that, forward/backward symmetry of lens focusing is broken with the focal volume shifts its center backwards when the symmetry of wave breaks and consequently astigmatic focusing arises and degrades tightness of focusing. The solution proposed is to apply laser intra-cavity spectrum modulation in two-photon fluorescence microscopy, with spatiotemproal focusing in photoexcitation beam. We envision that this work offers a general framework and strategy to understand and improve virtually any other wave-based application whose efficacy depends on optimal focusing, and may be helpful when information is transmitted by waves in applications from electromagnetic communications, to biological and astronomical imaging, and lithography etc.