Measuring the optical parameters of thin films by p-polarized laser beams

The refractive index n(f), extinction coefficient k(f) and thickness d(f) of a dip coated film are measured by using p-polarized laser beams. A sample is oblique illuminated with a p-polarized laser beam, and then two reflected beams, from the front and back surfaces, are received with a detector. After measuring their intensity ratio versus the angle of incidence, it is convenient to obtain the parameters of the film by means of data fitting. The films of polymethyltriethoxy silane (PMTES), which were made on a BK-7 glass substrate by dip coating, were measured. The method is non-contact, non-destructive and has the advantages of simplicity of both equipment and understanding. It is also shown that the values measured by this method are coincident with those measured by ellipsometry. (C) 1998 Elsevier Science Ltd. All rights reserved.