Interaction of Femtosecond-Laser-Induced Filament Plasma with External Electric Field for the Application to Electric Field Measurement

Abstract

The global monitoring of electrical processes in the atmosphere may become a very important part of environment control and prevention of disasters. Here we overview the theoretical and experimental studies on the radiation of laser filament plasma in an external electric field that clearly demonstrates the possibility of remote electric-field measurements. The recombination of air plasma in an external electric field depends on the field strength. The corresponding radiation of excited molecules (${\text {N}}_{2}^{*}, \text {O}_{3}^{*}$, and others) in the ultraviolet range is also sensitive to the field strength. In spite of plasma self-radiation that occurs even without an electric field, the fluorescence grows up even at low field strengths. Air plasma of laser filaments, induced by femtosecond laser pulses, is a good candidate for the remote field measurement. The most sensitive line for the field measurement may be the 337.1 nm line representing the $\text {N}_{2}^{*} (C^{3}) \,\rightarrow \, \text {N}_{2} ({B}^{3})$ transition. The fluorescence power at 337.1 nm is shown to increase exponentially with the field strength.