Plasma Enhancement of fs-Filament in N2-O2Mixture With ns-Heating Pulse

An intense femtosecond laser pulse propagating in air creates a consistent and repeatable plasma filament, whereas a nanosecond plasma generation is an avalanche-driven process, offering less control over the plasma formation process. The combination of the femtosecond and nanosecond laser pulses provides the ability to control the generated plasma with desired characteristics. This work investigates the amplification of the electron density in femtosecond laser filaments caused by a nanosecond heating pulse in air and nitrogen, employing detailed plasma kinetic modeling and experimental measurements of the electron density. Key aspects of the plasma revival and the properties of plasmas generated using dual laser pulses are presented. Computational studies demonstrated the revival of the femtosecond laser filament plasma to high electron densities (n_e ∼ 10^23 m^-3) using a nanosecond heating pulse, with the stochastic transition to breakdown identified as the limiting factor in experimental observations. Combined computational and experimental analyses indicate that sustaining plasmas at lower electron densities (n_e ∼ 10^21 m^-3) is consistently achievable, offering potential for controlled low-temperature plasma applications.