  The femtosecond transinet optical spectroscopy is employed to study the
relaxation dynamics of the equilibrium and hidden metastable
charge-density-wave states in single crystals of 1$T$-TaS$_{2-x}$Se$_{x}$ as a
function of the Se doping $x$. Similarly to pristine 1$T$-TaS$_{2}$, the
transition to a hidden phase is observed at low temperature after a quench with
a single 50~fs laser pulse, in the commensurate Mott phase up to $x=0.6$. The
photo-induced hidden-phase formation is accompanied by a notable change in the
coherent phonon spectra, and particularly the collective amplitude mode. While
the stability of the hidden phase with increased temperatures is only slightly
dependent of the Se content the hidden-phase creation-treshold fluence strongly
increases with the Se content from 1 to $\sim4$ mJ/cm$^{2}$.
