Advanced 2D periodic array and full transversal mode suppression

In this work, we present an improved version of the 2D periodic array from [Yoon et al, IUS2012, [1]]. Using a 2D P-matrix simulation tool, required COM (coupling of modes) parameters and periodic Δv/v waveguide parameters were optimized for desired 2D behavior. On this basis, the fine-tuned real geometries were determined. In the analysis of such a resonator, we introduce a novel approach in analogy to a multiple quantum well structure in solid state physics. It turns out that the optimized 2D periodic array with geometry variations fully suppresses all unwanted transversal modes within a certain bandwidth. Besides, prominent peaks by the transversal periodicity are also distinctively suppressed at the frequencies where the wavelength of the y-components of the transversal modes is comparable to the transversal pitch (p_T), i.e., near k_v=π/p_T. Therefore the 2D periodic array on the electrodes can be readily employed in designing SAW filters in SiO₂-covered LiNbO₃ with excellent performance.