High-performance magnetostatic wave resonators based on deep anisotropic etching of gadolinium gallium garnet substrates

Magnetostatic wave resonators based on yttrium iron garnet (YIG) are a promising technology platform for future communication filters. Such devices have demonstrated better quality factors than acoustic resonators in the 7 GHz range and above. However, the coupling coefficients of these resonators have been limited to less than 3%, primarily due to the restricted design space that is a result of microfabrication challenges related to the patterning of gadolinium gallium garnet (GGG), the substrate material used for growing single-crystal YIG. Here we report magnetostatic wave resonators created through the anisotropic etching of GGG substrates. Our approach, which is based on the YIG-on-GGG platform, uses a transducer with a hairclip-like structure. It is created by developing a microfabrication methodology that involves thinning and deep etching (up to 100 μm) of the GGG substrate. The resulting magnetostatic wave resonators exhibit a coupling of more than 8% in the 6–20 GHz frequency range. A microfabrication methodology that involves thinning and deep etching of gadolinium gallium garnet substrates can be used to create magnetostatic wave resonators that exhibit a coupling of more than 8% in the 6–20 GHz frequency range.