Design of Reflectivity-Based Surface Plasmon Resonance Optical Sensors for Ultrasound Detection

Sensors based on surface plasmon resonance present attractive features for the detection of narrow acoustic pulses since they can behave as quasi-point detectors. In order to detect fast ultrasound pressure waves, the system senses the intensity of the reflected beam for a fixed angle of incidence and for a fixed wavelength. Therefore, optimal conditions for Kretschmann's glass-metal-water configuration are presented. Optimization is performed by means of numerical simulations of the reflectivity curves for different low-cost metallic films with different thicknesses and angles of incidence. Zn, Ti, Cr, Al, and Cu are evaluated and compared with Au. In addition, the wavelength selection is discussed, and the oxidation effects are also briefly analysed.