The authors regret that one of the coauthors was inadvertently omitted in the previous paper[1]. E. Varene was a member of the Institut fr Festkrperphysik at the Technische Universitt Berlin and contributed to the results on cross-phase modulation. The authors regret that one of the coauthors was inadvertently omitted in the previous paper. [1]. E. Varene was a member of the Institut fr Festkper per ys ysik at the Technische Universitt Berlin and contributed to the results on cross-phase modulation.