Canceling and inverting normal and anomalous group-velocity dispersion using space-time wave packets

Abstract: Angular dispersion can counterbalance normal group-velocity dispersion (GVD) that increases the wave-vector length in a dispersive medium. By tilting the wave vector, angular dispersion reduces the axial wave number in this case to match the pre-GVD value. By the same token, however, angular dispersion fails to counterbalance anomalous GVD, which in contrast reduces the wave-vector length. Consequently, GVD-cancellation via angular dispersion has not been demonstrated to date in the anomalous dispersion regime. We synthesize here structured femtosecond pulsed beams known as `space-time' wave packets designed to realize dispersion-cancellation symmetrically in either the normal- or anomalous-GVD regimes by virtue of non-differentiable angular dispersion inculcated into the pulsed field. Furthermore, we also verify GVD-inversion: reversing the GVD sign experienced by the field with respect to that dictated by the chromatic dispersion of the medium itself.