GUIDED-WAVE CHARACTERIZATION TECHNIQUES FOR THE COMPARISON OF PROPERTIES OF DIFFERENT OPTICAL COATINGS

The specific behavior of optical thin films very often leads to limita tions of optical system performance. Accurate characterization techniq ues for evaluating film properties are necessary to understand this be havior. Characterization techniques based on the propagation of guided waves in the thickness of the films appear to be very useful. We repo rt our particular way to determine the refractive index and the thickn ess of both isotropic and anisotropic thin films. Guided-waves techniq ues are sensitive enough to detect slight variations of thin film opti cal constants, so we use them to study the variations of refractive in dex versus temperature. From this we can obtain the thermorefractive c oefficients partial derivative n/partial derivative T of our layers. M oreover, we can obtain, in some cases, the nonlinear refractive index coefficient. We also measure guided-wave attenuation and laser damage threshold with a digital imaging system. These means, dependent on gui ded waves, are used in combination for a comparative analysis of TiO2 and Ta2O5 layers made by different deposition techniques (conventional evaporation, ion assisted deposition and ion plating).