Acoustoelectric Non-Reciprocity in Lithium Niobate-on-Silicon Delay Lines

Abstract

Lamb wave delay lines with acoustoelectri-cally-induced non-reciprocity are demonstrated in suspended lithium niobate-on-silicon waveguides for the first time. An electric current is fed through the silicon layer in the same axis as the piezoelectrically-transduced acoustic waves which are attenuated or amplified depending on the direction of the energy exchange with drifting electrons (i.e. acoustoelectric (AE) effect). Therefore, the insertion loss (IL) and non-reciprocity of the delay line is adjustable by controlling the current bias which varies the electron drift velocity and the subsequent momentum transfer. Proof-of-concept delay lines in the range of 600 MHz to 700 MHz are demonstrated with a fractional bandwidth as high as 2.8% and AE gain as high as 5.6 dB resulting in ~20 dB of non-reciprocity. These non-reciprocal components could offer a monolithic and dynamically-tunable solution to the numerous issues that arise from the increasing congestion and interferences in the telecommunication spectrum and suggests the possibility of developing fully-switchable low-IL delay lines through design/fabrication optimizations.