Rayleigh wave diffraction

The appearances of these devices are very similar to that of Rayleigh mode devices, but a thin solid film or grating is added to prevent wave diffraction into the bulk. 

Francisco J. Sanchez-Sesma Mechel Campillo. 1991. Diffraction of P, SV, and rayleigh waves by topographic features A boundary integral formulation. Bulletin of the Seismological society of America, 81 2234-2253. 

Fig. 12.10. Time-resolved S(f, y) along a line perpendicular to a crack in glass, scanning across the crack (a) some distance from the end of the crack (b) 75 //m from the end of the crack. As in Fig. 9.3(b), the horizontal axis is time t the vertical axis is y, and the value of S(t, y) is indicated by the intensity, with mid-grey as zero and dark and light as negative and positive values of S. In both figures, the first echo (seen as the first stripy vertical bar) is the geometric reflection from the surface of the specimen, and the second echo (seen as the second stripy vertical bar) is the Rayleigh reflection ( 7.2). The patterns forming a x are the reflections from the near and the far sides of the crack, which cross over when the lens is directly above the crack. In (b), where the scan passes quite near to the tip of the crack, the hyperbolic pattern is due to the crack-tip-diffracted wave (Weaver et al. 1989).

Consider a plane light wave with wave vector k, which falls on the liquid-air surface containing thermal ripples with a small amplitude. Rayleigh found that if the illuminated surface area is much larger than A and each component (p,a) gives a first-order diffracted light wave... 

The diffraction of light waves in such a film can be treated in the same way used by Rayleigh, that is, applying (macroscopic) Maxwell equations with the appropriate boundary conditions at both surfaces. Afterward it was found that the same answers are obtained when the interference of the reflected, refracted, and diffracted waves are treated in an elementary fashion by adding the diffraction of the single surfaces with appropriate phase factors. 

In the forced Rayleigh scattering technique, the diffraction lattice of the excited state is formed by the interference of the two laser fluxes. A probe laser then follows the disappearing process of this lattice [21], The disappearance process of this lattice reflects the lifetime of the excited state T and molecular diffiision D. A plane wave laser light with a wavelength X is divided into two and they cross each other at an angle q to observe the interference pattern with a period A. In the constructive interference area, the probe will be excited and the striation of the excited state can be observed. Period A of the striation is expressed as... 

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