A High Sensitivity Transparent Ultrasound Transducer Based on PMN-PT for Ultrasound and Photoacoustic Imaging
Haoyang Chen, Shubham Mirg, Mohamed Osman, Sumit Agrawal, Jiacheng Cai, Ryan Biskowitz, Josiah Minotto, Sri‐Rajasekhar Kothapalli
Abstract
We recently introduced piezoelectric lithium niobate (LN) based transparent ultrasound transducers (TUT) as a new platform for developing multimodal optical, ultrasound, and photoacoustic imaging (PAI) systems. However, LN based TUT is limited in its signal-to-noise ratio due to material's low piezoelectricity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_{33}$</tex-math></inline-formula> ). In this letter, we report, for the first time, a 0.2-mm-thick transparent lead magnesium niobate-lead titanate (PMN-PT) based TUT (PMN-PT-TUT) for ultrasound and photoacoustic applications and compared its performance with a 0.25-mm-thick transparent LN based TUT (LN-TUT). To improve the ultrasound energy transmission efficiency, TUTs were fabricated with a two-matching-layer design. This resulted in a dual frequency response with center frequencies of 7.8 MHz/13.2 MHz and corresponding bandwidths of 28.2%/66.67% for PMN-PT-TUT, as well as center frequencies of 7.2 MHz/11.8 MHz and bandwidths of 36.1%/62.7% for LN-TUT. The optical transmission rate of PMN-PT-TUTs and LN-TUTs are measured as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 73 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 91%, respectively, at 532 nm optical wavelength. The PMN-PT-TUT exhibited higher sensitivity compared to LN-TUT with a nearly threefold higher pulse echo amplitude and more than twofold higher photoacoustic amplitude. Furthermore, optical resolution photoacoustic microscopy experiments on phantom targets demonstrated lateral resolutions of 7 and 5.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m and axial resolutions of 285.6 and 375.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m for PMN-PT-TUT and LN-TUT, respectively. These results indicated that PMN-PT is a viable alternative to LN for developing TUT based multimodal ultrasound and PAI systems.