Abstract
We have investigated photon-induced changes of optical parameters of amorphous Ge
20
Bi
10
Se
70
thin films due to illumination by laser irradiation. Absorption peaks were detected in the tailing area in the wavelength range between 300 and 600 nm. These peaks reduced to two peaks in the higher dose (9 J/cm
2
). The optical energy gap E
gd
was found to have the well known direct-allowed transition mechanism. Values of E
gd
show that all films exhibit a photo-induced photo-darkening effect indicated by a red shift of E
gd
. The higher laser dose shows an increase in E
gd
values. The effect of laser on other optical constants was also investigated. The refractive index (n), extinction coefficient (k) and dielectric constant of irradiated films were also calculated.