Second Harmonic Generation during Femtosecond near IR Laser Pulse Filamentation in Air

Abstract

Second harmonic generation during filamentation of femtosecond laser pulses in atmospheric air is investigated. Based on the analysis of spatial and spectral characteristics of the second harmonic, key factors affecting its generation are identified, such as the laser pulse energy and focusing conditions. The conversion efficiency to the second harmonic is on the order of ~10^–10. The obtained results deepen the understanding of nonlinear interactions inside laser filaments and open new prospects for practical applications in atmospheric sensing and related fields.