Transverse modes suppression and loss reduction for buried electrodes SAW devices

High coupling substrates using overcoat layers of silicon oxide for temperature compensation exhibit a strong affinity toward multi-mode behavior. Apodization, which is the standard technique to suppress the transverse modes, suffers from drawbacks such as reduction of the transduction efficiency and additional losses. By changing the transducer layout, the guiding can be improved and a "piston mode" can be obtained. This approach is demonstrated on resonators and DMS test devices manufactured on lithium niobate with an orientation close to YX128 deg.