Monitoring sub-surface chemical reactions in heterogeneous materials using wavefront-shaping-assisted bidirectional focusing

We have developed a bidirectional focusing microscope that utilizes feedback-assisted wavefront shaping to focus light inside a heterogenous material in order to monitor subsurface chemical reactions. The bidirectional geometry is found to provide superior intensity enhancement relative to single-sided focusing, owing to increased mode control and long-range mesoscopic correlations. Also, we demonstrate the microscope's capability to measure sub-surface chemical reactions by optically monitoring the photodegradation of a Eu-doped organic molecular crystal embedded in a heterogeneous material using both fluorescence and Raman spectroscopy as probe techniques. (C) 2022 Optica Publishing Group