Electrical reflection coefficient and velocity shift for groove gratings

The electrical reflection coefficient r/sub e/ and velocity shift ( Delta nu / nu )/sub e/ for grooves has never been formulated. All previous calculations for r/sub e/ and ( Delta nu / nu )/sub e/ have used formulas valid for the reflection of a surface acoustic wave (SAW) from an array of conducting strips. However, the discontinuity in electrical boundary conditions leading to these formulas does not exist in groove gratings. A new expression for the electrical reflection coefficient and velocity shift for some material overlays is derived from both the variational principle and perturbation theory. The results for various substrates are compared to show the agreement between the two approaches. The implications of this new formulation for the design of grooved arrays on various materials are discussed, effectively resolving the discrepancy between theory and experiment.< >