Al and MgF_2 multi-layer filters and their environmental stability
Al and MgF2 metal-dielectric multi-layer filters have been fabricated by thermal and electron beam evaporation.Influences of vacuum annealing at 100 ℃,150 ℃,200 ℃ and 300 ℃ respectively for 40 min on spectrum,morphology and environmental stability have been analyzed.For all samples,results show that after annealing,rms roughness reduces,maximal transmittance and half width increase.During the storage of the samples in desiccated chamber,the locations of the maximal transmittances have shifted much toward long wavelength,the maximal transmittances reduce and the restrain abilities of visible spectrum weaken for the as-deposited and 300 ℃ annealed samples.While the locations of the maximal transmittances have little shift,the maximal transmittance and the restrain ability of visible spectrum keep unchanged for the 150 ℃ and 200 ℃ annealed samples,showing excellent environmental stability.