  Conventional theories of electromagnetic waves in a medium assume that only
the energy of the field propagates inside the medium. Consequently, they
neglect the transport of mass density by the medium atoms. We have recently
presented foundations of a covariant theory of light propagation in a
nondispersive medium by considering a light wave simultaneously with the
dynamics of the medium atoms driven by optoelastic forces [Phys. Rev. A 95,
063850 (2017)]. In particular, we have shown that the mass is transferred by an
atomic mass density wave (MDW), which gives rise to mass-polariton (MP)
quasiparticles, i.e., covariant coupled states of the field and matter having a
nonzero rest mass. Another key observation of the mass-polariton theory of
light is that, in common semiconductors, most of the momentum of light is
transferred by moving atoms, e.g., 92% in the case of silicon. In this work, we
generalize the MP theory of light for dispersive media and consider
experimental measurement of the mass transferred by the MDW atoms when an
intense light pulse propagates in a silicon fiber. In particular, we consider
optimal intensity and time dependence of a Gaussian pulse and account for the
breakdown threshold irradiance of the material. The optical shock wave property
of the MDW, which propagates with the velocity of light instead of the velocity
of sound, prompts for engineering of novel device concepts like very high
frequency mechanical oscillators not limited by the acoustic cutoff frequency.
