Method to minimize the effects of polarizer leakage on reflectivity measurements.

The effects of polarizer leakage on reflectivity measurements have been determined analytically and experimentally. It is shown that for values of the extinction ratio larger than 10(-3) the inferred refractive index of dielectric materials from reflectivity measurements maybe in error by 27% or more. On the other hand, the real and imaginary parts of the index of carbonaceous materials may be in error by more than 30 and 60%, respectively. Furthermore, when the specularity index of smooth surfaces is to be determined, significant differences (68% or more) may result for the same range of values of the extinction ratio. A method is presented for correcting the reflectivity measurements for polarizer leakage based on the extinction ratio of the polarizer. In addition, analytical expressions are provided for the determination of the actual value of the extinction ratio of a given polarizing film at any wavelength. The effects of the typical and actual values of the extinction ratio on the inferred optical constants and specularity index of dielectric and absorbing materials are assessed.