Novel Testbed for Acoustoelectric Loss Analysis in Lamb Wave Lithium Niobate on Silicon Delay Lines

This work reports a novel method for isolating the loss associated with the energy coupling between acoustic phonons and electrons in Lamb wave (S0) lithium niobate (LN) on silicon (Si) delay lines. Said coupling, also known as the acoustoelectric effect (AE), can be leveraged for analog signal processing, hence, gaining a fundamental understanding of its limitations is crucial for developing novel AE devices. By taking advantage of the strong dependance of the AE effect on the electrical resistance experienced by the acoustic waves, it is shown that it is possible to isolate the contribution of AE loss to the overall device response. An AE loss of ~44 dB/mm and mechanical loss of ~32 dB/mm (Si underlayer) is derived by comparing the response of testbed delay lines made of LN and LN-on-Si with and without overlaying thin metal film.