  Wakes are medium perturbations created by a moving object, such as wave
patterns behind boats, or wingtip vortices following an aircraft. Here, we
report about an experimental study of an uncharted form of parabolic wakes
occurring in media with the group velocity twice larger than the phase
velocity, as opposed to the conventional case of Kelvin wakes. They are formed
by moving a laser spot on a thin plate, which excites a unique wake pattern
made of confocal parabolas, due to the quadratic dispersion of the zero-order
flexural Lamb mode. If the spatial dimensions are rescaled by the perturbation
velocity and material constant, we obtain a single universal wake with constant
parabolic focal lengths. We demonstrate an evanescent regime above the critical
frequency where the wave components oscillate exclusively in the direction
parallel to the perturbation path, with an opening angle of 90{\deg}. We define
a dimensionless number analogous to Froude and Mach numbers, which determines
whether the complete parabolic wake pattern will be excited by the moving
source or not.
