The variations in structure and optical properties of amorphous a-Se and a-M5Se95 (M = Ge, Ga and
Zn) films have been studied based on FTIR and optical measurements. FTIR transmittance spectra for a-Se and
a-M5Se95 (M = Ge, Ga and Zn) glasses were measured as a function of wavenumber. The addition of Ge, Ga and Zn
increases the vibrational frequency of the a-Se main band. The absorption edge of Ge5Se95 shifted towards long side
of the wavelength in comparison with that of a-Se film. This shift increases gradually in the case of Ga5Se95 and
Zn5Se95 films. So, the optical bandgap ofM5Se95 films was decreased, but the index of refraction was increased. The
first and third order of electric susceptibility (χ(1) and χ(3)) and non-linear index of refraction (n2) were increased
by adding Ge, Ga and Zn into a-Se.