Mechanical stress and optical properties of Ge35Sb5S60 films

•SHG is combined with mechanical stress measurements to investigate film optical nonlinearities.•Double-layer model gives an evidence of the stress origin of the observed SHG.•Internal part of the film gives main contribution to SHG.

Transmission and reflection spectra, mechanical stress and generation of the second optical harmonic are investigated in the films of Ge35Sb5S60 chalcogenide glass. It is shown that good correlation between mechanical stress and nonlinear properties can be achieved by introducing to SHG model an inactive layer located at film–air border.