Measurement of complex refractive index of metals from polished bulk samples

An optical polarization-based reflection technique is proposed here to determine absolute refractive index of metal. The sample metal surface is introduced in the path of monochromatic beam of light which is linearly polarized such that the magnitudes of the s and p states are identical in the reflected beam. The reflected beam passes through a linear polarizer placed prior to a photodetector. The phase difference between these orthogonal states of polarization is evaluated by combining two intensity measurements with two different orientations of the output polarizer. The magnitude of the said phase difference in the visible region being unique within the range of values of real and imaginary components of the refractive index, the complex refractive indices of metals can be evaluated. The salient feature of the proposed technique is that, two intensity measurements taken from single reflection can potentially yield the required parameters. Experimental results for three different metals are presented.