Lithium Niobate on Silicon Lamb Mode Acoustoelectric Waveguide With 5.5 Db Sustained Terminal Gain

Abstract

In this work, sustained terminal gain is reported for the first time in micromachined lithium niobate (LN) on silicon (Si) Lamb mode waveguides through acoustoelectric amplification. In such acoustically thin waveguides, the large coupling between the Lamb waves and the drifting electrons in Si gives rise to a very efficient transfer of momentum from electrons to elastic phonons, rendering the waveguide a traveling wave amplifier. In a geometrically optimized waveguide, up to 5.5 dB terminal gain is achieved by dissipating less than 6.5 milliwatts of DC bias power. This is measured for input RF signals up to -20 dBm and gain compression is observed for larger inputs with its characteristic impacted by the DC bias level and the device geometry. Further design improvements are expected to increase the terminal gain, hence, justifying the implementation of micro-acoustic RF amplifiers.