Kilometer-range nonlinear propagation of femtosecond laser pulses

Abstract

Ultrashort, high-power laser pulses propagating vertically in the atmosphere have been observed over more than 20 km using an imaging 2-m astronomical telescope. This direct observation in several wavelength bands shows indications for filament formation at distances as far as 2 km in the atmosphere. Moreover, the beam divergence at 5 km altitude is smaller than expected, bearing evidence for whole-beam parallelization about the nonlinear focus. We discuss implications for white-light Lidar applications.

Optimal laser-pulse energy partitioning for air ionization

“…An interplay between focusing by the Kerr effect and defocusing effects including ionization and the saturation of the Kerr effect [18,19] ensures intensities in the range of several tens of TW/cm 2 over long distances [20,21].…”

Femtosecond Filamentation in Air

“…The formation of filaments at kilometric distances in the sky was also reported from the detection of the supercontinuum by a telescope [70,89]. During an horizontal propagation campaign led with the Teramobile laser [52,54,90], the presence of multiple filaments up to 600 m was clearly demonstrated from step by step measurements of the plasma density using three different techniques (conductivity measurements, detection of the luminescence and detection of the sub-THz EMP).…”

“…This demonstrates that the organized features of the filament are governed more by the input pulse than by shot to shot fluctuations or air turbulence. The energy exchange between the background energy reservoir and the filaments constitutes the process sustaining the propagation, extinction and nucleation of filaments over long distances [52,54,70].…”

“…For ultrashort pulses, multiphoton absorption therefore occurs in steps of small amount of energy. This explains the propagation over long distances of an intense fs laser pulse, To summarize, the most spectacular properties of light filaments are: a) Their propagation over long distances from the meter scale in the laboratory to the kilometric scale outdoor [29,52,54,70].…”

Nitrogen fluorescence induced by the femtosecond intense laser pulses in air

“…In previous works, experimental research in the field of filamentation created filaments typically a few metres in the laboratory [17][18][19] and over hundreds of metres Correspondence to: S. Li and M. Jin, Institute of Atomic and Molecular Physics, Jilin University, Changchun, Jilin Province 130012, China. Email: suyu11@mails.jlu.edu.cn, mxjin@jlu.edu.cn at a range of few kilometres in the atmosphere [20][21][22] , making the remote sensing possible. Since the intensity of plasma fluorescence is related to that of the laser beam, plasma fluorescence spectra along the propagation path can be used to characterize the femtosecond filamentation process.…”