In the present report the fabrication techniques involving the post-growth gamma-irradiation for the preparation of low-threshold saturable absorbers based on silica films activated by semiconductor nanometer-sized crystals (nanocrystals - NCs) of technologically controllable size and space ordering are reported. The modification of the optical spectra in the NC-composed films is determined by room-temperature comparative investigations of the photoluminescence (PL) and nonlinear optical (NLO) parameters of the samples of high-pure and semiconductor (ZnSe, CdS and CdSe) NC-composed fused-silica films before and after irradiation for various exposure conditions. An emission band centered at 432 nm (~2.87eV), excited at 352-360 nm and exhibiting a strong silica nanoparticle dispersion dependence, was detected for unirradiated samples. The observation of the modification of the violet luminescence band (432 nm) and the appearance of the red luminescence band at wavelengths of 620-650 nm for gamma-irradiated samples are reported. The parameters of optical nonlinearities detected in silicon dioxide films composed by various semiconductor NCs are also analyzed before and after gamma-irradiation of different dozes. The results are discussed in the frames of structural models reported in the literature.