Improved performance of piezoelectric transparent ultrasound transducers using electrical impedance matching circuit

Transparent ultrasound transducers (TUTs) have gained significant traction in the fields of photoacoustic (PA) and ultrasound (US) applications. TUTs possess the unique capability to transmit and receive ultrasound waves while maintaining optical transparency. As a result, TUTs simplify the PA imaging process and facilitate seamless integration with other optical imaging modalities. However, the limited sensitivity of TUTs has been a primary challenge hampering their widespread adoption in PA setups. One often overlooked factor contributing to this limitation is the electrical impedance mismatch between the transducer and the data acquisition system. Here, we designed and studied the utilization of a filter-based electrical impedance matching (EIM) circuits to enhance the sensitivity of lithium niobate-based TUTs. In our approach, the fabricated TUTs incorporate a quarter-wavelength Parylene-C matching layer and epoxy as a backing layer. Our results demonstrate that the integration of the EIM circuit yields substantial improvements in the sensitivity, bandwidth and axial resolution of both pulse-echo US signals and PA signals. PA imaging of leaf phantoms were compared with and without EIMs to further showcase the performance enhancements that can be achieved by integrating EIM with TUTs. Overall, these results demonstrate that EIM circuits can be employed to improve the performance of TUTs.