The degree of the photodoping process in Ag(100[.angs.])/a-Se$_{75}$Ge$_{25}$(1500[.angs.]) films has measured as a function of the photon energy between 1.5[eV] and 2.9[eV] with the exposing time. The "window" characteristics of Ag occur at 3400[.angs.] (3.65[eV]) and Ag is almost transparent in this region. It is shown that transmittance is almost constant (40-50%) for the wavelength ranges of our experiment. It is found that the energy gap of a unexposed a-Se$_{75}$Ge$_{25}$ film is 1.81[eV]. Ag photodoping process results in the photodarkening effect which the absorption edge shifts to the long wavelength. Especially, very large band shift (-0.3[eV]) is obtained by exposing He-Ne laser(6328[.angs.]).. We have obtained "the U-type property" for Ar He-Ne and semiconductor laser. It is associated with the variation of energy gap(E$_{g}$) with photo-dose and substantially is explained by DWP model.l.gap(E$_{g}$) with photo-dose and substantially is explained by DWP model.