  We present a new scheme to create all-optical tunable and lossless waveguide
using a controllable coherent Raman process in an atomic rubidium vapor in
N-type configuration. We employ a Gaussian Raman field and a Laguerre-Gaussian
control field to imprint a high-contrast tunable waveguide-like feature inside
the atomic medium. We numerically demonstrate that such a waveguide is able to
guide arbitrary modes of a weak probe beam to several Rayleigh length without
diffraction and absorption. Our results on all-optical waveguide based scheme
may have potential application in lossless image processing, high contrast
biomedical imaging and image metrology.
