Interpretation of the spectrally resolved far field of femtosecond pulses propagating in bulk nonlinear dispersive media

It has previously been realized that angle-resolved spectra (or far-field spectra) reflect in detail the complex dynamics of femtosecond pulses propagating in nonlinear dispersive media [J. Opt. Soc. Am. B 22, 862 (2005)], and thus represent a potentially useful experimental diagnostic tool. In this paper we extend an effective three-wave mixing approach previously applied to nonlinear X-waves [Phys. Rev. Lett. 92, 253901 (2004)] to the analysis of far-field spectra. Theoretical justification for the approach is presented, and a practical method is proposed that makes it possible to interpret all features of far-field spectra, and to extract quantitative information about the underlying intra-pulse dynamics.