Photoacoustic Raster Scan Imaging Using an Optomechanical Ultrasound Sensor in Silicon Photonics

Abstract

To address challenges in ultrasound detection for photoacoustic computed tomography, an optomechanical ultrasound sensor (OMUS) was developed in silicon photonic microchip technology. Such sensors are small (20 mu m), sensitive (NEP 1.3 mPa Hz(-1/2)), broadband (measured 3 - 30 MHz), and scalable to a fine-pitch matrix. This optical sensor has extreme sensitivity by combining an acoustic vibrating membrane with an innovative optomechanical waveguide. In this work, we test this sensor for photoacoustic computed tomography (PACT) by measuring and imaging the photoacoustic response of small 10 mu m diameter sutures. Sensor signal-to-noise ratio (SNR), image contrast-to-noise ratio (CNR), and image resolution for different sensor geometries are characterized. We conclude that the sensor behaviour is in line with theory and meets the requirements for future applications in photoacoustic tomography.