  We frame the transverse Anderson localization of light in a one-dimensional
disordered optical lattice in the language of localized propagating eigenmodes.
The modal analysis allows us to explore localization behavior of a disordered
lattice independent of the properties of the external excitation. Various
localization-related phenomena, such as the periodic revival of a propagating
Anderson-localized beam are easily explained in modal language. We characterize
the localization strength by the average width of the guided modes and carry
out a detailed analysis of localization behavior as a function of the optical
and geometrical parameters of the disordered lattice. We also show that in
order to obtain a minimum average mode width, the average width of the
individual random sites in the disordered lattice must be larger than the
wavelength of the light by approximately a factor of two or more, and the
optimum site width for the maximum localization depends on the design
parameters of the disordered lattice.
