Complex optical constants on a subwavelength scale

Optical phase contrast has for the first time been observed on a nanometer scale, with a near-field microscope of scattering type that maps the comple te optical field of amplitude and phase. Backed by quasielectrostatic theor y, we demonstrate the significance and experimental accessibility of even c omplex optical constants on a subwavelength scale. Further, our method can separate the near-field response from background artifacts and thus is expe cted to enable nanoscale optical mapping of even topography-rich objects su ch as resonant clusters and macromolecules.