Micro electric fields detection improvements: Steps toward tailoring cold atmospheric pressure plasma

Cold atmospheric plasma science is a continuously growing domain. From microfabrication to medicine, air and surface decontamination, agriculture, material synthesis, food processing, among many more, applications of this omnipresent, yet to broad society invisible technologies seems limitless. The knowledge about plasma sources and the underlying physics is constantly improved with new designs and multidisciplinary applications. The ability of cold atmospheric pressure plasma to generate reactive species relevant for the most prominent applications, such as wound healing, pathogen inactivation, methane reforming, originates from the plasma's electric field characteristics. It is thus of the utmost importance to have an efficient, sensitive, and high-resolution detection techniques to determine the plasmas electric field time and space resolved. This allows to unravel its role in the behavior of plasmas for each respective application. Our method of choice is electric field-induced second harmonic, a by now well-established nonperturbative technique for measuring the amplitude and orientations of cold atmospheric plasma electric fields. Although E-FISH allows for a good and tunable time resolution, depending on the pulse's characteristics of the used laser, it has been shown that E-FISH presents some issues with spatial resolution and sensitivity. Work on enhancing these two characteristics of E-FISH have been made by our team and collaborators. Using a femtosecond laser, novel approaches were developed and optimized. The presented results confirmed the improvement of the electric field detection technique, the E-FISH, and will certainly deepen our knowledge on the spatio-temporal electric field distribution of cold atmospheric plasma.