  Recent techniques have allowed transition metal dichalcogenides (TMD)
monolayers to be grown and adequately characterised. Of particular interest,
their nonlinear optical response presents many promising opportunities for
future nanophotonic devices and technology. The dispersion of the carriers is
trigonally-warped, leading to an anisotropic Fermi surface for low-lying
states. In this paper, the effects of such a deformation on the nonlinear
harmonic generation are studied by considering a tight-binding model expanded
up to third order in $\mathbf{k} \cdot \mathbf{p}$. By solving exactly the
free-carrier dynamics of the carriers when interacting with intense and
ultrashort pulses of light, we predict the photogenerated current in a
nonperturbative way and study its harmonic composition. We find frequency and
amplitude modulation of the nonlinear current in quadratic and cubic models.
Furthermore, we demonstrate anisotropy-induced modulation of the intensity of
higher-order harmonics and the existence of harmonic crossovers, depending on
the incident light polarisation. The methodology presented in this paper may be
applied to any general effective two-band model and offer a pathway to identify
signatures of electronic features in optical output.
