M.Sc Thesis

M.Sc StudentRavi Kumar Resmi
SubjectUltrasound Detection via Polymer-Coated
Silicon-Photonics-Based Sensors
DepartmentDepartment of Electrical and Computer Engineering
Supervisor ASSOCIATE PROF. Amir Rosenthal
Full Thesis textFull thesis text - English Version


In biomedical applications, ultrasound detection is conventionally performed with piezoelectric transducers. Due to its opacity and reduced sensitivity upon miniaturization, there is a need for the development of new detection methodology. Recently, ultrasound detection has been demonstrated with waveguides fabricated in silicon-on-insulator substrates. Ultrasound detection via silicon waveguides relies on the ability of acoustic waves to modulate the effective refractive index of the guided modes. However, the low photo-elastic response of silicon and silica limits the sensitivity of conventional silicon-on-insulator sensors.

In this thesis work, we explore a hybrid approach to enhance the sensitivity of ultrasound detection that combines silicon-on-insulator-based resonators with acoustic materials. In particular, we show that using a transparent polymer with a high photo-elastic coefficient as an over-cladding can significantly increase the acoustic response and reduce the sensor’s susceptibility to surface acoustic waves and acoustic reverberations. Our experimental results are in good agreement with the theoretical analysis and reveal that the response enhancement of the sensor depends on the proportion of the mode that is exposed to the polymer over-cladding. Finally, preliminary optoacoustic imaging measurements have been performed, demonstrating the appropriateness of our approach for designing all-optical optoacoustic systems.