Ultrasound imaging remains an indispensable tool in numerous medical disciplines ranging from oncology to cardiology and from dermatology to ophthalmology. Imagers employing piezoelectric and capacitive micromachined transducers have long been the golden standard when it comes to traditional ultrasonography procedures such as abdominal, pelvic or obstetric scans. However, when used in endoscopic, intravascular, and catheterized applications, traditional receiver implementations have demonstrated serious shortcomings in terms of power dissipation and achieved form factor.

The focus of this thesis is on the development and realization of an electronic-photonic ultrasound receiver system capable of tackling modern miniaturized endoscopic probe specifications. It begins with an overview of the existing electrical and optical ultrasound imaging technologies, which spotlights the need for an alternative approach to endoscopic ultrasound sensing and proposes a electronic-photonic array system based on micro-ring resonator (MRR) sensors as a promising candidate. Subsequently, the operating principle of MRR ultrasound sensing is presented, accompanied by theoretical analysis and finite element model (FEM) simulations of the transduction mechanisms. The developed theory is backed by proof-of-concept experimental results. The initial analysis is followed by the design and fabrication of a first-of-its-kind ultrasound receiver array on a silicon photonic chip with highly sensitive, micro-scale optical MRR sensors in its core. Such a system can be ultra-low power and size, ensuring safe operation inside the human body without sacrificing key system attributes, such as image resolution and system bandwidth. Configured in 2-D beamforming arrays of thousands of elements, these optical sensors, can perform real-time, 3-D imaging and pave the way towards miniaturized optical ultrasonic reception probes with form factors below 5mm3, compliant to modern endoscopic probe specifications. After presenting measurement results of this electronic-photonic system-on-chip (EPSoC) prototype, the thesis discusses architectures that will further enhance the overall system sensitivity through the use of coherent detection and higher quality factor MRRs.




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