Light-propagation and imaging in planar optical waveguides

Planar optical waveguides, permitting light-propagation in only two dimensions, can be used to form images of one-dimensional objects. In one arrangment, the paths of light-rays on the guide are determined by the distribution of the effective refractive index over the regions of the guide, resulting in two-dimensional optical systems. Another possibility, existing in thick, multimode planar guides is the utilisation of self-focussing or self-imaging properties. All these imaging methods are reviewed, with particular emphasis on the most recent method of self-imaging.