  An $\it{ab \,\, initio}$ based fully microscopic approach is applied to study
the nonlinear optical response of bulk Tellurium. The structural and electronic
properties are calculated from first principles using the shLDA-1/2 method
within density functional theory. The resulting bandstructure and dipole matrix
elements serve as input for the quantum mechanical evaluation of the
anisotropic linear optical absorption spectra yielding results in excellent
agreement with published experimental data. Assuming quasi-equilibrium carrier
distributions in the conduction and valence bands, absorption/gain and
spontaneous emission spectra are computed from the semiconductor Bloch and
luminescence equations. For ultrafast intense off-resonant excitation, the
generation of high-harmonics is evaluated and the emission spectra are
calculated for samples of different thickness.
