OPTICAL-CONSTANTS OF THIN-FILMS BY MEANS OF A POINTWISE CONSTRAINED OPTIMIZATION APPROACH

The present paper considers the calculation of the absorption coeffici ent, the index of refraction, and the thickness of thin films using op tical transmission data only. To solve the problem, a pointwise constr ained optimization approach is used. The method consists of defining a nonlinear programming problem, efficients to be estimated with linear constraints that represent prior I;knowledge about the physical solut ion. Numerical experiments using artificially generated transmission d ata show that the method is reliable, even in cases where no interfere nce fringes exist. Examples are presented and discussed. (C) 1998 Else vier Science S.A.