Characterization of Thin ScAlN Film based Natural Single-Phase Unidirectional SAW Transducers using Sagnac Interferometer

Natural single-phase unidirectional surface acoustic wave transducers were reported previously for oriented quartz, LiNbO3, LiTaO3, La3Ga5SiO14 substrates, etc. However, the directionality in the thin piezoelectric films hasn't been reported elsewhere till recently by our group. The motivation to utilize the directionality in thin piezoelectric films was to improve the transducers or delay line's return loss effectively such that it can be utilized in integrated sensor applications. For characterization of directionality, in this paper we utilized Sagnac interferometer. We compared the forward and backward acoustic signals for propagation direction (i) parallel to the c-axis tilt and (ii) perpendicular to the c-axis tilt. The directionality produces higher acoustic signals on the backward direction as compared to the forward direction because of orientation being in that direction. But if the wave propagation is perpendicular to the c-axis tilt, the acoustic signals in either direction produce same power. Also, in this paper we report the delay line's return loss characteristics for open, PNR and short type of reflectors.