Super-resolution stimulated Raman scattering microscopy with the phase-shifted spatial frequency modulation

We present a unique super-resolution stimulated Raman scattering (SRS) microscopy technique based on phase-shifted spatial frequency modulation (PSFM) under wide-field illumination, permitting super-resolution chemical imaging with single-pixel detection. Through projecting a series of the pump and Stokes laser patterns with varying spatial frequencies onto the sample and combining with the proposed π-phase shift, the higher spatial information can be rapidly retrieved by implementing the fast inverse Fourier-transform on the spatial frequency-encoded SRS data. We have derived the theory of the PSFM-SRS technique for super-resolution imaging. Our further modeling results confirm that PSFM-SRS microscopy provides a ∼2.2-fold improvement in spatial resolution but with a much-reduced laser excitation power density required as compared with conventional point-scan SRS microscopy, suggesting its potential for label-free super-resolution chemical imaging in cells and tissue.