Characterization of a novel Optical Micro-machined Ultrasound Transducer

We design and demonstrate a prototype ultrasound sensor based on a photonic micro-ring resonator integrated on a silicon membrane, and show that it can detect very low pressure ultrasound waves. The use of integrated photonics in future array transducers has several benefits: for instance it provides a small spatial footprint, compatibility with MRI due to the lack of electrical wiring, easy interrogation of the array of elements and ease of mass production, which may result in cost-effective fabrication of array transducers. To understand the working principle of the sensor, we have modeled the basic sensor element, fabricated the sensor and measured the response of the sensor to ultrasound. We have studied the response of the optical resonator separately before we integrate the resonator on the membrane and measure the response of the entire sensor. Besides the characterization of the sensor, we have expanded the existing knowledge of acoustical noise to determine the noise mechanism of the sensor.