Several types of ultrasound sensors have been developed and are used in the field of medical imaging. Conventional transducers are made of piezo-electric material and show good practical performance. However, when the piezo-electric elements need to be small (below 100 μm × 100 μm), these transducers face challenges in fabrication as well as the electrical impedance matching of the elements. As an alternative, we fabricated an optical micro-machined ultrasound transducer (OMUT). This sensor contains an optical micro-ring resonator, which is coupled to a photonic waveguide, and integrated onto an acoustical membrane. The OMUT is build with standard silicon-on-insulator (SOI) technology, allowing for easy fabrication. In this paper, we present the first measurement results of the sensor. Our prototype has a -6 dB bandwidth of 19% and a noise equivalent pressure (NEP) of 0.5 Pa. These first acoustical measurements show that this prototype may form the basis of future ultrasound transducers. ... Read more

Recently there has been a growing interest in sensing by means of optical microring resonators in photonic integrated circuits (PIC) that are fabricated in silicon-on-insulator (SOI) technology. Taillaert et. al. proposed the use of a waveguide based ring resonator as a strain gauge. However, the strong lateral confinement of the light in SOI waveguides and its corresponding modal dispersion was not taken into account. We present experimental results and understanding of the effects of an applied strain in the effective index in a SOI-PIC. In addition, we also investigated the influence of the waveguide geometry. ... Read more