Refractive index measurements of thin films using both Brewster and m-line technique: A combined experimental setup

We report on refractive index measurements of guiding and non-guiding films synthesized by the sol–gel technique. An experimental setup has been developed in our laboratory based on both m-line and Brewster angle methods. The main feature of the setup is the ability to perform both m-line and Brewster angle measurements on the same sample allowing a more accurate measurement of the refractive index. Moreover, using laser sources at different wavelengths, we are able to measure refractive index as a function of wavelength in the visible and near infrared spectral range. We have tested our experimental setup performing measurements on many guiding and non-guiding sol–gel films deposited by the spin-coating technique on glass substrates. Estimation of refractive indices for non-absorbing thin films with an accuracy and reproducibility to within 0.1%, in a spectral region from 532 nm to 780 nm, has been achieved.