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In this paper, the use of a structure comprising a thin LiNbO3 plate and a multilayered acoustic mirror composed of SiO2 and Pt for high-performance longitudinal leaky surface acoustic wave (LLSAW) device is proposed. The mirror is expected to offer a much higher reflectivity than that composed of SiO2 and AlN, which the authors proposed previously. The field distribution of these structures is calculated by using a finite element method. It is shown that the acoustic wave energy of the proposed structure is well confined in the vicinity of the top surface, and that leakage to the substrate is reduced. A one-port resonator is fabricated on the structure and its performance characteristics are evaluated. Owing to a high phase velocity of 6,035 m/s, which is about 1.5 times higher than that of conventional SAWs, a large impedance ratio of 71 dB was achieved at 3.5 GHz in addition to a large fractional bandwidth of 9.5%.

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The authors have proposed longitudinal type surface acoustic wave (SAW) devices comprising a LiNbO 3 thin plate, acoustic mirror, handle substrate and interdigital transducers (IDT). This paper describes the observational and theoretical validation of the proposed devices by using a laser probe system and finite element analysis (FEA). It is shown that the laser probe system based on the Sagnac interferometer is effective for direct observation of the devices operated at even 2 GHz range through the observation of SAW field distribution of the existence and lack of acoustic mirror, their comparison with FEA results and changes of the transverse mode pattern. In addition, a phenomenon of SAW radiation normal to the busbars from IDT is found both observationally and theoretically, and a possible radiation mechanism explaining the results is also discussed.

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