Low-Loss and High Power Handling Acoustic Delay Lines Using Thin-Film Lithium Niobate on Sapphire

In this work, we present the first group of GHz low-loss, wideband, and high power handling delay lines (ADLs) using a thin-film lithium niobate (LiNbO
3
) on sapphire platform. The ADLs leverage a single-phase unidirectional transducer (SPUDT) to efficiently excite the shear horizontal surface acoustic wave (SH-SAW) in the film stack. The fabricated miniature SH-SAW ADL at 1.1 GHz shows a low insertion loss (IL) of 2.8 dB, a wide fractional bandwidth (FBW) of 6.14%, and a fast phase velocity of 5127 m/s. The device also features a high 1 dB compression point (P1dB) of 30.4 dBm. The propagation characteristics of SH-SAW are extracted, with a group velocity of 4747 m/s and a propagation loss of 6.73 dB/mm. The simultaneously low-loss and high power handling illustrate the great potential of LiNbO
3
-on-sapphire for RF and cross-domain applications at GHz.