Membrane design of an all-optical ultrasound receiver

Ultrasound sensors such as piezoelectric transducers and CMUTs are successfully used for medical imaging. However, especially wiring of individual elements is difficult in the fabrication of small piezoelectric arrays, used in, e.g. the field of intravascular imaging. As an alternative, we designed a novel type of ultrasound receiver based on silicon-on-insulator technology. This receiver contains an optical microring resonator positioned on the acoustical membrane. The deformation of the membrane induces strain in the optical resonator resulting in an optical resonance shift that can be recorded.To determine whether this receiver is suitable as ultrasound sensor we designed three prototype elements and simulated their response. This paper presents the design and working principle of our ultrasound receiver and shows the modeling results of these elements. We found an optimum in the dimension of the element by varying the thickness with corresponding radius for a response at 1 MHz frequency using a finite element analyses. Furthermore we obtained a sensitivity of 3.4 microstrain/kPa when the response of a 80 μm element was modeled resulting in a minimum detection level of 590 Pa. The first acoustical simulations of a single element of this receiver array shows that it may be a suitable candidate for miniaturized non-electrical ultrasound receivers.