Ultra-Wideband Non-Reciprocal Micro-Acoustic Delay Lines with Slanted-Finger Interdigital Transducers

Ultra-wideband (UWB) Lamb wave delay lines with non-reciprocal transmission are demonstrated in a suspended thin-film lithium niobate (LN)-on-silicon (Si) platform. Using slanted-finger interdigital transducers (SFIT) to efficiently excite fundamental symmetric (S0) Lamb waves, up to 33% fractional bandwidth (6-dB) is realized at ~650 MHz. This is achieved through leveraging the strong interaction between drifting electrons in Si and piezoelectrically transduced acoustic waves - i.e. acoustoelectric (AE) effect - to compensate the problematic diffraction losses associated with SFIT and enable UWB non-reciprocal behavior. The non-reciprocity of the device is switched on and regulated by the bias applied along the device.