Characteristics of femtosecond laser induced filament and energy coupling by nanosecond laser pulse in air

Abstract

This study presents a detailed plasma kinetics model for laser-induced non-equilibrium plasmas in atmospheric pressure air, incorporating a self-consistent energy balance and refined rate expressions within a three-temperature framework. The model is validated against experimental data of femtosecond-laser-induced filaments, showing good agreement in electron dynamics and gas temperature. The analysis focuses on femtosecond filament decay kinetics and characteristic properties across varying initial electron densities and electron temperatures, including cases with oxygen addition and its influence on decay behavior. The study further examines energy coupling between the femtosecond filament and nanosecond laser pulse, identifying dominant kinetic pathways and optimal time delays through a comparative analysis of single-pulse and dual-pulse plasmas. Additionally, results indicate that temporal shaping of the nanosecond laser pulse intensity enhances dual-pulse performance relative to Gaussian pulses.