Delay lines based on a suspended thin film of X-cut lithium niobate

Abstract

We report on the fabrication, experimental characterization, and theoretical modeling of delay lines fabricated on a lithium niobate X-cut thin film substrate. We demonstrate the feasibility of fabricating delay lines on lithium niobate suspended thin films to take advantage of the high electromechanical coupling of Lamb waves in this material. Specifically, we design the delay lines with an orientation of 30° with respect to the Y axis to maximize the coupling coefficient for the propagation of the S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> mode. We show a maximum delay of 1.35 μs. Furthermore, the practically zero stress exhibited by the thin film point to the fact that larger delays could be easily achieved. The propagation loss measured is around 12 dB/cm, or equivalently, 7.5 dB/μs.