3D imaging of electric field vector profiles using oblique laser polarization based on electric-field-induced second-harmonic generation

As a non-contact, non-invasive, and highly sensitive method for measuring electric fields, the electric-field-induced second-harmonic generation (E-FISHG) has been attracting attention. In conventional vector measurement of electric fields, it is necessary to align the plane of polarization of the probe laser with the direction of the electric field vector to be measured, and to change the plane of polarization of the probe laser to measure both vertical and horizontal electric fields. In this study, we used a method of estimating the electric field vector profiles by determining the linearly coupled longitudinal and transverse electric fields along the laser optical path. This was achieved by injecting the probing laser polarization at an oblique angle and acquiring signals by separating the longitudinal and transverse components of the second harmonic wave. We have already proposed a method to restore a one-dimensional electric-field-profile from a sequence of E-FISHG signals along the probing laser path. Using these methods, we obtained the three-dimensional electric field vector profiles by changing the incident laser position in the vicinity of the parallel cylindrical electrodes with radii of 10 mm separated by 10 mm. We successfully obtained 3D imaging of the electric field vector profiles with a maximum error of 22%. This study demonstrates that the technique using probing laser polarization at an oblique angle is useful for measuring electric field vector distributions without changing the laser polarization angle.