two experiments that have used experimental parameters similar to ours [@Liu; @Yin]. In [@Shen], the totally reflected $p$-polarized wave is heterodyned with the $s$-polarized wave from the same laser source. In [@Yin], a position-sensitive detector produces a signal that is proportional to the difference of the lateral displacements of $s$- and $p$-polarized waves. Since an $s$ wave does not excite SPPs, the obtained signal gives the GH shift of the $p$-polarized wave in both cases. Following similar schemes, it will not be difficult to set up an experiment in the Otto configuration to test our results.

Conclusion
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In this paper, we have studied the influence of the surface plasmon excitation on the GH effect theoretically, when a Gaussian beam of a finite width is incident on a dielectric-metal bilayer in the Otto configuration. Using the invariant imbedding method, we have calculated the GH lateral shifts of the reflected and transmitted beams and the widths of these beams relative to that of the incident beam. We have found that the lateral shift of the reflected beam depends very sensitively on the thickness of the metal layer and the width of the incident beam. Close to the incident angle at which 