Observation of interference in reflection profile resulting from excitation of optical normal modes with focused beams.

We report the observation of novel interference patterns in reflected beam profiles resulting from the excitation with a focused laser beam of both the long-range surface plasmon mode and leaky waveguide modes in a prism-coupled thin-film geometry. Many new features of the observation are in good agreement with the theory; namely, the greater than unity normalized peak interference intensities, the monotonically decreasing spacing between the periodic intensity variations, and the reshaping of the reflected profile due to propagation. Implications of these results for submicrometer patterning in nanoscience are pointed out.