posed to be proportional to the local SP intensity and is further assumed isotropic with the same radial dependence as Ψ$_{I}$. As in Ref. 4 a maximum Bragg mirror reflectivity of 90% is found experimentally, we introduce this value as the only free parameter into the model. The thereby calculated SPs profile in Figs. 2(c) and 2(d) fit the experiment quite well. In a next step, we decrease the exiting intensity to prevent saturation in the images and thereby allow for quantitative measurement. In Figs. 3 and 4, we compare experiment and theory for different polarization angles θ of the exiting laser beam and, again, we find a good qualitative agreement. From the experimental data we extract the SP intensity in F 2 and plot it in Fig. 5 as a function of the polarization angle θ . Due to the angular dependence of the excitation, Ψ$_{I}$ must follow a cos ( θ ) law. The same is true for Ψ$_{R}$ due to interference of the SPs reflected by the protrusions. It is worth mentioning that these interferences come essentially from the angular dependence of the reflectivity of the mirror [10] and not from the complex phase factor e ik SP L which is constant for every SP light path of length L = 2 a connecting F 1 and F 2 to any points on the mirror. The total intensity then obeys a [cos ( θ )] 2 law which is perfectly reproduced [11] by the experimental data extracted from Fig. 3 and plotted in Fig. 5. In summary, we have elaborated an elliptical Bragg reflector acting as a corral for SP waves. SP propagation is observed using a LR microscope which allows quantitative observations and comparison with a theoretical model. By launching a SP wave at F 1 we observe numer- ous fringes and a strong focalization in F 2 . We can finally realize an angular interferometer by rotating the polarization of the exciting laser beam. In all cases the observations are in qualitative as well as quantitative agreement with our model. For financial support the Austrian Science Foundation and the European Union, under Project Nos. FP6 NMP4-CT- 2003-505699 and FP6 2002-IST-1-507879, are acknowledged [1] H. Raether, Surface Plasmons (Springer, Berlin, 1988). [2] B. Hecht, H. Bielefeldt, L. Novotny, Y. Inouye, and D. W. Pohl, Phys. Rev. Lett. 77, 1889 (1996). [3] S. I. Bozhevolnyi and F. A. Pudonin, Phys. Rev. Lett. 78, 2823 (1997). [4] H. Ditlbacher, J. R. Krenn, G. Schider, A. Leitner, and F. R. Aussenegg, Appl. Phys. Lett. 4