Fields of optical waveguides as waves in free space

It is shown by using the scalar diffraction theory and the method of images that the arbitrary field confined by the optical waveguide can be generated in free space by the appropriate light source. The correspondence between the guided and free-space waves is illustrated using several particular fields, such as the diffraction-free, self-imaging, ultra-short, solitonlike, partially coherent waves and laser fractals. In opposition to the eigenmode theory of waveguides, the field at the guide entrance can satisfy neither the guide wave-equation nor the boundary conditions.