Optical and mechanical property changes in thin-film filters with post deposition thermal treatments

Abstract

In this paper, we report the effects of two types of filter with post deposition thermal treatments: one effect is the central wavelength of thin-film narrow-band-pass filters increasing with increasing post-deposition annealing temperature above 250 degrees C, which is a permanent bake-shift effect. It therefore appears possible to "tune" the stress of narrow-band-pass filters by this post-deposition annealing to shift center wavelength. The other effect is the position of T-50% wavelength of a dichroic mirror shifting with increasing Substrate temperature, which is the condition under which that dichroic mirror operates inside a projector. A dichroic mirror was deposited oil different types Substrate for comparison of the amplitude of T-50% wavelength shift. We can predict the shifts in wavelength and choose the most appropriate substrate material for a dichroic mirror to obtain a T-50% wavelength change minimum, i.e., to avoid it color change of the projection image. Mechanical properties Such as stresses in Ta2O5, TiO2, Nb2O5, and SiO2 single layer films fabricated by different deposition processes are investigated in this study.