Multiphoton structured thin-plane imaging with a single optical path

Optical sectioning has become an indispensable technique for high-speed volumetric imaging in the past decade. Here we present a novel optical-sectioning method that produces a thin plane of illumination by exploiting the spatial and temporal properties of multiphoton excitation. Critically, the illumination and detection share the same optical path, as in a conventional epi-fluorescence microscope configuration. Therefore, the imaged sample can be prepared as for standard fluorescence microscopy. Our method also leads to a laterally structured illumination pattern, and this feature can be utilized in structured illumination microscopy to further enhance the imaging performance. We show an example of such an approach, which achieves axial resolution finer than confocal microscopy. We also demonstrate the potential of the new method for biological applications by performing three-dimensional imaging of living Caenorhabditis elegans.