Passive In-Band RF Power Sensing in Thin-Film Lithium Niobate on Silicon Platform

A frequency selective and passive method for RF power sensing is reported that leverages the interaction of guided Lamb waves and electrons in thin-film lithium niobate (LN) on silicon (Si). The incoming RF signal is first transduced into Lamb waves via the piezoelectricity of LN and is then converted into an electron flow in the Si. The generated direct current (DC) is proportional to the RF power and appears only within the passband frequency of the waveguide which is defined lithographically by the interdigital transducers (IDT) lateral dimensions. Preliminary results show at least 30 dB dynamic range and faster than 1 ms response time. The reported dynamic range is believed to be far from the full potential of this scheme and could be improved by design/optimization, thus, enabling realization of integrated power sensors in micro-acoustic domain.