Measurements of the polarization states (represented by complex numbers χ r and χ t , respectively) of light reflect ed and transmitted by an unsupported or embedded thin film, for totally polarized light (with nonzero p and s com ponents) incident at 45°, permit simple, direct, and explicit determination of the film's complex refractive index N 1 independently of film thickness or input polarization. If a = χ r /χ t , we find that a = r s + r s -1 , where r s is Fresnel's complex reflection

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... fficient of the ambient-film interface for the s polarization at 45° incidence. From a,r s is determined, and from r s we get N 1 = N 0 (1 + r s 2 ) 1/2 /(1 + r s ), where N 0 is the refractive index of the transpar ent medium surrounding the film. Knowledge of the incident polarization χi allows the film thickness to be deter mined, also explicitly, by using either of the ratios χ i /χ r or χ i /χ t .