We demonstrate how the resolution and imaging depth limitations of nonlinear optical microscopy can be overcome by modulating the spatial overlap between two-color pulses. We suppress out-of-focus signals, which limit the imaging depth, by a factor of 100, and enhance the lateral and axial resolution by factors of 1.6 and 1.4-1.8 respectively. Using spatial overlap modulation, we demonstrate background-free three-dimensional imaging of fixed mouse brain tissue at depths for which the signals of the conventional technique are swamped by background noise from out-of-focus regions.
Keywords: (170.5660) Raman spectroscopy; (180.2520) Fluorescence microscopy; (180.4315) Nonlinear microscopy; (190.4180) Multiphoton processes.