Flatness of planar Fabry-Pérot cavities: a critical parameter for high sensitivity sensors for photoacoustic imaging (Conference Presentation)

The manufacturing process of high sensitivity planar Fabry-Perot (FP) sensors for Photoacoustic (PA) imaging is very challenging and typically results in non-uniformities of the cavity thickness. The non-uniformities leads to an angular tilt between the two mirrors forming the FP sensor. Based on a full wave model, we study the impact of this tilt which reveals a strong dependence between optical sensitivity and degree of tilt. As an example, an angular tilt as small as 0.1 mrad can reduce the sensitivity by 75%. To achieve high sensitivity FP sensors, high mirror reflectivities are required which in turn increases the impact of the non-uniformities in the cavity thickness. Therefore, the optimal design of the sensors is dependent on the manufacturing precision.