Second order reflection effects in normal and oblique incidence gratings

A general formulation is derived for calculating the first- and second-order (in the overlay height) effects in a SAW (surface acoustic wave) grating as a function of incidence angle and overlay material parameters. In general, the second-order effects detected experimentally exist both for normal and oblique incidence grooved gratings. The existence of a velocity shift at the first harmonic and reflection coefficient at the second harmonic for groove gratings at nearly all angles of incidence is demonstrated. The existence of these effects for metallic gratings is shown, although the character of these effects is quite different from that in the grooved case