Interferometric phase-dispersion microscopy

We describe a new scanning microscopy technique, phase-dispersion microscop y (PDM). The technique is based on measuring the phase difference between t he fundamental and the second-harmonic light in a novel interferometer. PDM is highly sensitive to subtle refractive-index differences that are due to dispersion (differential optical path sensitivity, 5 nm). We apply PDM to measure minute amounts of DNA in solution and to study biological tissue se ctions. We demonstrate that PDM performs better than conventional phase-con trast microscopy in imaging dispersive and weakly scattering samples. (C) 2 000 Optical Society of America OCIS codes: 040.2840, 110.0180, 110.4500, 12 0.5050, 170.3880.