Ultrasound imaging has long been one of the most indispensable tools in numerous medical disciplines ranging from oncology to cardiology and from dermatology to ophthalmology. In endoscopic, intravascular and catheterized applications, which constitute a huge part of the point-of-care (POC) spectrum of applications, traditional ultrasonic imagers employing piezoelectric and capacitive micromachined ultrasound transducers (CMUTs) have demonstrated serious shortcomings in terms of power dissipation and achieved form factor. Thus, new, alternative approaches to ultrasound sensing are being sought.
Optical solutions are recently gaining popularity, since moving the transduction of the ultrasonic signal to the optical domain remotes the power hungry receive electronics outside the probe tube, and consequently the human body. On top of that, replacing electrical transducers greatly simplifies packaging, eliminating most electrical connections and interfaces, relying on extremely compact optic fiber arrays instead of micro-coax cables to carry the ultrasonic modulation. Lastly, and specifically in this work, optical micro-ring resonator (MRR) sensors have been proven to mitigate the sensitivity-bandwidth tradeoff of their piezo and CMUT counterparts with extremely small footprint.
This talk will outline the process of building a first-of-its-kind electronic-photonic SoC prototype, focusing on multiple system aspects from platform choice and device operation to circuit design and system architecture. First, the operating principle of our main sensing element, the MRR will be analyzed from the theory of the underlying transduction mechanisms to the experimental verification of its ultrasound sensing capability. Then, a dual-chip sensing-receiver system architecture will be presented, and the respective specifications will be translated to circuit design choices. The designed electronic-photonic SoC has been fabricated in unique monolithic platform, which enables tight co-integration of high-performance photonic devices with fast CMOS transistors, in a commercial, high-volume foundry. Experimental results from the fabricated SoC will be shown, demonstrating its functionality and showcasing the first real-time optical ultrasound beamforming array that simultaneously interrogates multiple MRR sensors in a wavelength division multiplexing (WDM) scheme. Finally, future directions to higher sensitivity structures and a path towards a multi-modal, all-optical ultrasound probe will be discussed.
Dr. Panagiotis Zarkos received the Diploma in Electrical and Computer Engineering from the National Technical University of Athens in 2015 and the MSc and PhD degrees in Electrical Engineering and Computer Science (EECS) from the University of California (UC), Berkeley, in 2019 and 2021, respectively. His PhD research focused on an electronic-photonic ultrasound sensing system on chip, for which he was awarded the Ross N. Tucker Memorial Award by the EECS Department of UC Berkeley. He is currently working as an Integrated Circuit (IC) Design Engineer at Lawrence Berkeley National Laboratory, where he specializes in subatomic particle detector instrumentation circuits. Panagiotis has also been awarded the Teaching Effectiveness and Outstanding Graduate Student Instructor Awards for teaching the introductory course to electrical engineering at UC Berkeley. He has held an internship position at the PHY Research Laboratory, Intel Corporation, Hillsboro, OR, where he worked on silicon photonic transceiver architectures. His research interests include the design, modeling, and prototyping of integrated systems on chip targeting biomedical imaging and sensing applications, and subatomic particle detectors.