Supercontinuum generation of ultrashort laser pulses in air at different central wavelengths

摘要

Supercontinuum generation by femtosecond filaments in air is investigated fordifferent laser wavelengths ranging from ultraviolet to infrared. Particularattention is paid on the role of third-harmonic generation and temporalsteepening effects, which enlarge the blue part of the spectrum. Aunidirectional pulse propagation model and nonlinear evolution equations arenumerically integrated and their results are compared. Apart from the choice ofthe central wavelength, we emphasize the importance of the saturation intensityreached by self-guided pulses, together with their temporal duration andpropagation length as key players acting on both supercontinuum generation ofthe pump wave and emergence of the third harmonics. Maximal broadening isobserved for large wavelengths and long filamentation ranges.