Propagation of self-focusing laser pulses in atmosphere: experiment versus numerical simulation

Numerical simulations of self-focusing laser pulses obtained via a slowly evolving wave approach (modified nonlinear Schrodinger equation) are compared with published experimental results in fused silica as well as with experimental results in air and fused silica obtained in our laboratory. The mathematical model includes group-velocity dispersion and third-order dispersion, optical shock, and both instantaneous Kerr and delayed Raman nonlinearities as well as a perfectly matched layer absorbing boundary condition. Second-harmonic frequency-resolved optical gating data taken after 10.91 m of propagation allow a direct comparison between experimental and computational envelopes at a number of pulse energies. FWHM measurements of the spectral width, intensity autocorrelation duration, and pulse radius at distances of 4.35, 10.91, 17.47, and 22.73 m provide a view of model fidelity across both energy and propagation distance variables. The magnitude of the nonlinear refractive index, n(2), is inferred. (C) 2004 Optical Society of America.