On the Phase Shift Accompanying Reflection of Light from Evaporated Films and the Change of Effective Refractive Index as Function of the Thickness of Deposit

For the calculation of phase shift accompanying reflection from a thin film on base medium, the author used the surface of hypothetical single medium with an effective refractive index for the surface of lamella with one layer oh base medium and expanded this method into the case of reflection from multiple layers on base medium. The phase shift and effective refractive index as function of the evaporated thickness were calculated in the limited cases of interest in optical practice, and if the dielectric deposit is evaporated and this lamella has the thickness with minimum or maximum resultant reflectivity, the following relations will be established at these thicknesses : I) n term of effective refractive index turns to minimum or maximum value, respectively, II) k term of effective refractive index turns to zero in all cases, III) the curve of phase shift corresponds to the point of inflexion. These relations also hold true in multiple dielectric layers on a base medium. The phase shifts of air/aluminium, air/[aluminium (opaque) + ZnS], air/[aluminium (opaque) + MgF_2(λ_0/4) +ZnS] interfaces were observed as a function of the thickness of final film from the displacement of Fizeau fringe.