The optical performance of anti-reflective coatings in iodine-filled absorption cells

We investigate the optical performance of anti-reflective coatings subject to high temperatures and the presence of iodine gas to determine the most suitable technological process for iodine-filled absorption cell production. Two unwanted effects need to be avoided or mitigated. One is the settling of iodine gas in the coating structure, which reduces the transmittance of the cell windows. The other is the thermally induced spectral shift which limits the effect of the antireflective coating. We investigate the thermal resistance of TiO2 and Ta2O5 based coatings produced by electron beam evaporation (e-beam) and plasma ion-assisted deposition (PIAD). We prepared sets of quartz samples subject to a range of temperatures and the presence of iodine gas. We show that the choice of the coating technique and annealing procedure can mitigate the aforementioned effects.