A novel sensitive scheme for determining the optical parameters of thin films by p-polarized reflectance

We present a novel sensitive scheme for the measurement of optical parameters of thin films, based on the theory of optical admittance and data fitting. A p-polarized laser beam falls on the glass surface at theta(i), and two beams with intensities I-a and I-b reflected from the front and the rear surface of the glass are detected by a CCD. The characteristics of the angular modulation of the reflectance ratio gamma (gamma = I-a/I-b) are closely related to the optical parameters of the thin film, namely the refractive index n(f), extinction coefficient k(f) and thickness d(f). By means of measuring the angle distribution gamma (theta(i)) and fitting the results with theoretical data, the optical parameter of the films can be obtained easily. For several types of samples, such as surface layers of glass, single films and multilayer films, we provide preliminary experimental results demonstrating that the scheme has the advantages of simplicity and high sensitivity, which make it widely applicable to the fields of surface analysis, film measurement and photochemical sensors.