Sum frequency generation microscopy for imaging chirality*

Optically active sum frequency generation microscopy was demonstrated for the first time. Using films of solution of chiral 1,1'-bi-naphthol molecules with microstructures, we showed that sum frequency generation microscopy can image molecular chirality with three-dimensional sectioning capability and sub-micron spatial resolution. Because the image contrast originates from the intrinsic chirality of the system, no staining is required. Our microscopy scheme also allows the simultaneous detection of two-photon fluorescence. As a result, optically active sum frequency generation microscopy can be potentially very useful for live cell imaging. Preliminary results of applying this technique to DNA conformation study will also be described.