Dielectric optical interfaces in total internal reflection for ultrasound detection

Abstract

In this work we carry out a detailed analysis of the design and performance of an optical quasi-point ultrasound detector for optoacoustic tomography. The detector is a two-dielectric system based on a glass prism (for light coupling) and water. The behaviour of the system is analyzed for six different modes of operation that arise from monitoring the amplitude and phase of the electric field of the reflected optical beam. For both amplitude and phase monitoring, we consider modes of operation centered on parallel and perpendicular components of the electric field individually and a differential mode (parallel-perpendicular). For each operation mode, we estimate the best set of parameters (refractive indices and angle of incidence). We verify that the optimum performance, in terms of sensitivity, is obtained when the angle of incidence of the interrogation beam is close to the critical angle. The best performance for operation modes based on monitoring an individual parameter is obtained by means of glass prisms with low refractive index, whereas for differential modes of operation higher refractive indices are preferred. We verify the linearity of each configuration by means of the numerical calculation of the total harmonic distortion