Theory for a magnetostatic surface wave grooved reflector grating

The magnetostatic surface wave (MSSW) reflection characteristics of a uniform grating of shallow grooves etched on the planar surface of an epitaxial YIG film are treated using an approach which integrates field theory with the coupled-mode approach well-known in the area of optical gratings. The MSSW reflectivity of a grating comprised of a varying number of trapezoidal (but almost rectangular) grooves is computed for the case in which the surface of the YIG film is metallized after the grooves are etched. It is found that this reflectivity is significantly larger than the surface-acoustic-wave (SAW) reflectivity of an equivalent grating on a LiNbO
3
substrate. A particularly attractive feature of the present structure is the absence of bulk-wave loss which, in the case of SAW resonators, represents an important factor limiting the maximum achievable Q.