Supercritical focusing coherent anti-Stokes Raman scattering microscopy for high-resolution vibrational imaging

We report the development of, to the best of our knowledge, a novel supercritical focusing coherent anti-Stokes Raman scattering (SCF-CARS) microscopy for high-resolution vibrational imaging. Two optimized phase patterns with a combination of concentric rings with an alternative 0 and π phase are generated by using a spatial light modulator and applied to the pump beam for minimizing its focal spot size. One of the phase patterns is for both the lateral and axial resolution enhancement, and the other can further improve the lateral resolution, but it sacrifices the axial resolution to some extent. We demonstrate this high-resolution SCF-CARS microscopy technique by imaging the polymethyl methacrylate (PMMA) nano-cylinder on a microscope slide and glass-air interface, as well as biomedical samples, for example, tooth.