Influences of temperature and stress on transmission characteristics of multilayer thin-film narrow bandpass filters

In this study, an analytical model is developed to evaluate the effects of uniform and nonuniform temperature increases, as well as stress level, on t he optical characteristics of three-cavity sub-nanometer bandpass filters f abricated using TiO2, and SiO2, film materials through ion-assisted deposit ion (IAD), taking into account the coupled photoelastic and thermo-optical effects. A more realistic stress analysis, which is capable of considering the effects of intrinsic and thermal stresses, bending moment as well as no nuniform temperature increase, is proposed and formulated for the first tim e. Various factors, including errors in film thickness, changes of refracti ve index and film thickness due to temperature increase and stress as well as the delamination gap along the layer interface, are then considered to e valuate their individual influence on optical characteristics of bandpass f ilters. The results show that the change of film thickness due to temperatu re increase and stress has a significant effect on center wavelength shift. Moreover, a significant degradation of the transmission curve due to nonun iform temperature increase was observed.