Method and system for stimulated Raman microscopy beyond the diffraction limit

摘要

Systems and methods for probing a Raman signature of a sample with a resolution exceeding the diffraction limit are described. These systems, called GASSE (Gain Saturated Stimulated Emission) and iGASSE (interferometric GASSE), are detecting a Raman signal produced in a sample located at the focal spot of a Gaussian pump pulse. Two additional pulsed laser beams (Stokes beams), a central Stokes beam having a Gaussian beam profile and another Stokes beam having an annular beam profile, are also focused to the focal spot. The spatial and temporal phases of the laser pulses are adjusted to produce destructive interference over most of the temporal width of Stokes pulses, which causes emission from the central Stokes beam to narrow well below the diffraction limit. A two-dimensional image of the sample is produced by scanning the combined beams across the sample. The system may find applications in biomedical and semiconductor technology.