Spectral response of chirp-dependent femtosecond laser filamentation in air

Abstract

Filamentation is a nonlinear optical phenomenon that involves the interplay between Kerr lens self-focusing and plasma defocusing, holding promise for practical applications in open-air environments over long distances. This process significantly alters the characteristics of laser pulses, making the control of laser properties a pivotal issue. In this study, we investigated the effects of laser energy and chirp on the spectral modulation of femtosecond laser pulses caused by filamentation in air. Negatively and positively chirped pulses exhibit distinct characteristics in the spectra measured after the filamentation. Negatively chirped pulses have broader spectral broadening and a stronger dependence on initial laser energy than positively chirped pulses, making them suitable for generating few-cycle pulses and applications requiring white light. In contrast, positively chirped pulses can be advantageous for applications requiring long-distance transmission of high-energy laser pulse. Our findings reveal the fundamental characteristics of femtosecond laser filamentation in air, thereby expanding the scope of possible atmospheric applications. © 2023, The Korean Physical Society.