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The influence of a sinusoidal surface corrugation of a thin silver film on the damping and the phase velocity of surface plasma oscillations is determined quantitatively. The experimental results are compared with theoretical calculations on the basis of a theory developed by Kretschmann and Kroger.

We investigated the phase velocity and the damping of guided light modes in wavy waveguides. A pronounced dependence of the damping on the angle α between the propagation direction of the mode and the groove lines was observed whereas the phase velocity remained unaffected within the accuracy of the measurement. Coupling processes between the various guided modes caused strong discontinuities in the dispersion curves.

The propagation velocity and damping of surface plasmons on sinusoidally modulated gold- and silver surfaces with different grating constants (ca. 4000 A, 8000 A and 15000 A) are measured at wavelengths of 6471 A and 5682 A as function of the amplitude of the grating (up to ca. 300 A). Earlier measurements of the changes of the dispersion relation produced by the sinusoidal profile could be improved by reducing the contribution of a second harmonic to the grating profile to less than about 0.06. Observed and calculated data, obtained with the Rayleigh method, show good agreement.

Using an ATR-arrangement guided modes are excited in a system of quartz/Ag/LiF/air layers. The excitation of the light modes is observed either by the reflection minimum at the resonance angle or by the maximum of the scattered light due to the coupling of light modes with photons via the roughness of the LiF film. The field distribution of the s-mode inside the LiF film allows to attribute the scattered light to the roughness of the LiF/air boundary. The evaluation of the measurements using the modes m s = 0−5 gives the roughness spectrum | s (Δ k )| 2 within the range of spatial frequencies 10 -4 A -1 ⩽ Δ k ⩽ 3 × 10 -3 A -1 . Assuming a gaussian correlation function a value of the r.m.s. height δ = 40−50 A is obtained. The observations show that the linear theory of plasmon scattering is valid at these r.m.s. heights if one probes with light modes m s ⩾ 0. Probing with the TM 0 ( m p = 0) mode (surface plasmon) which has its maximum field in the rough boundary and which has thus a stronger interaction with the roughness, the validity of the linear theory goes lost already beyond 20−30 A.

The influence of superficial layers on the plasma resonance emission produced on silver surfaces is studied as function of the dielectric constant and thickness of the surface films. Very thin tarnishing films can be detected in this way.

Light modes are excited in thin polyurethane films (freely supported) and LiF films (bounded by a silver film). They are registered by the radiation which is emitted from the rough film surface. The dispersion relation together with the observed position of the s and p modes allows one to determine the refractive index and thickness of the polyurethane film whereas in the case of LiF one needs a small anisotropy of the optical properties (≈ 1%) of the film to fit the observed data. The refractive indices could be determined within an error of about 10 −4 .