Rapid 3D Photoacoustic Imaging Technique Based on Chalcogenide On-Chip Micro-Ring Sensor Array

Optical resonators are now essential in modern sensing applications, particularly in photoacoustic imaging technologies. Among these, three-dimensional photoacoustic computed tomography (3D-PACT) emerged as a significant area of research. This sophisticated technique involves two critical phases: first, the optical capture of acoustically scanned signals, and second, the optoelectrical demodulation of these acoustic responses. In this study, we present groundbreaking research on both facets and introduce a novel 3D-PACT system aimed at enhancing imaging performance. This system employs an array of 20 chalcogenide (Ge₂₅Sb₁₀S₆₅) micro-ring resonators (MRRA) as the acoustic sensors, each micro-ring resonator featuring a radius of 20 µm and an average quality factor (Q-factor) of 5.5×10⁵. Simultaneously, a digital optical frequency comb (DOFC) technique is introduced for parallel spectral detection and acoustic signal demodulation within the MRRA. By utilizing on-chip thermal electrodes to tune the resonance wavelengths of 20 micro-ring resonators, the DOFC method enables efficient parallel spectral demodulation of the MRRA, reducing the scanning time in the PACT by a factor of 20 compared to a single sensor. We demonstrate the performance of the 3D-PACT system using cross-sectional hair strands and leaf skeletons. The MRRA-based 3D-PACT system is a promising tool for structural, functional, and molecular imaging of deep biological tissues.