  We investigate the effect of disorder on the propagation of surface plasmon
polaritons in arrays of evanescently coupled dielectric loaded surface plasmon
polariton waveguides. Diagonal disorder is implemented by randomly varying the
heights of the waveguides. Real-space as well as Fourier-space images of the
surface plasmon polariton intensity distribution in the waveguide arrays are
recorded by leakage radiation microscopy. With these techniques we
experimentally demonstrate the transverse localization of surface plasmon
polaritons with increasing disorder.
