Investigation of a p-i-n dual-cavity E-field photonic sensor

Photonic sensors are widely used for the measurements of broadband electromagnetic fields because they are constructed with dielectric materials, thus inducing minimal perturbation of the electric field under investigation and being mostly independent of electromagnetic interference. In this paper, the modeling and design of a high sensitivity electric field sensor, based on a whispering-gallery-mode resonator coupled with a Fabry-Perot cavity in silicon-on-insulator (SOI) technology, is presented. The sensing element consists of a p-i-n diode with a forward bias, implemented in an optical rib waveguide. A comparative study is performed between three waveguides with different transverse dimensions, in terms of propagation losses and effective mode index variation as a function of measuring electric field. Finally, the transmission spectrum of the complete sensor has been evaluated and a comparison between the results for each structure has been carried out. The study has been performed by a multiphysics simulation tool based on the finite element method (FEM).