Diffraction-free femtosecond optics

Radiation forces and confinement of neutral particles into the pulse envelope. New regime of collision ionization

“…As a result, analytical expression for the longitudinal density force and density potential of Gaussian laser pulse propagating in gaseous media is obtained. The recent theoretical and experimental results for diffraction-free regime [6] and nonlinear wave guiding propagation [7][8][9] of ultra-short femtosecond laser pulses, facilitate and enable the simplification and integration of these densities utilizing the first order of dispersion approximation in optics. Consequently, an effective longitudinal potential and force, acting in the media at level of the pulse width are obtained.…”

“…Thus, the spot of the pulse does not change significantly at distances less than one diffraction length. There is also possibility to enlarge this distance up to few diffraction lengths, using fs pulses in diffraction free regime [6] and in nonlinear wave-guiding regime with power slightly higher than the critical for self-focusing [7][8][9] propagates in air. In these regimes the transfer shape (the spot) of the pulse does not change of few diffraction lengths, and the flow of energy is in a surface orthogonal to the propagation direction.…”

“…The investigations in the previous section point that a confinement into the pulse envelope of neutral atoms or molecules (nitrogen's N and oxygen's O2) in air can be realized by femtosecond optical pulses, propagating in diffraction-free regime (with power values less than the critical one for selffocusing [6]) or in nonlinear wave-guiding regime [7][8][9]. These regimes correspond to initial pulse energy in the range from 10 nJ up to 1-2 mJ (pulse duration around…”

Nonparaxial solitons in air

“…Here, it is important to mention that the nonparaxiality leads to diffraction-free (waveguiding) regime of propagation of femtosecond pulses with the initial shape of light disks (δ 2 = d 2 0 /z 2 0 ). In this case, their transverse size (d 0 ) is much bigger than the longitudinal one (z 0 ) [29]. The waveguiding regime allows reducing the 3D + 1 task to 1D + 1 problem in the same manner as in optical fibers.…”