White light generated by femtosecond optical vortex beams
P. Hansinger, G. Maleshkov, I. L. Garanovich, D. V. Skryabin, D. N. Neshev, A. Dreischuh, and G. G. Paulus
In this work we report detailed experimental and numerical investigation of the white light generation by singly- and doubly-charged optical vortices propagating in a Kerr medium, where spectral broadening and transfer of topological charge (TC) into emerging spectral satellites takes place due to self-phase modulation and degenerate four-wave frequency mixing (FWFM). Experiments performed with different pump beams show an excellent agreement with theory. Singly- and doubly-charged white light vortices are observed within more than ±200nm bandwidth after nonlinear propagation in Argon gas. Our experiment and theory data confirm that the topological charge transformation of the newly-generated spectral components follow a law analogous to the one for the energy conservation in the FWFM process. We also present results on the white light vortex stability.
OCIS codes: (190.0190) Nonlinear optics; (190.4380) Nonlinear optics, four-wave mixing; (260.6042) Singular optics.