Showing papers by "Hervé Rigneault published in 1994"

Guided-wave characterization techniques for the comparison of properties of different optical coatings

Abstract: The specific behavior of optical thin films very often leads to limitations of optical system performance. Accurate characterization techniques for evaluating film properties are necessary to understand this behavior. Characterization techniques based on the propagation of guided waves in the thickness of the films appear to be very useful. We report our particular way to determine the refractive index and the thickness of both isotropic and anisotropic thin films. Guided-waves techniques are sensitive enough to detect slight variations of thin film optical constants, so we use them to study the variations of refractive index versus temperature. From this we can obtain the thermorefractive coefficients ∂ n /∂ T of our layers. Moreover, 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 guided waves, are used in combination for a comparative analysis of TiO 2 and Ta 2 O 5 layers made by different eposition techniques (conventional evaporation, ion assisted deposition and ion plating).

Interpreting anisotropy and disturbances of optical properties of thin films in terms of layer microstructure

Abstract: Consequences of the columnar microstructure of dielectric thin films deposited by conventional vacuum evaporation are discussed. A model associated with the columns is used together with in situ and in air measurements to show that the anisotropy of Ion Assisted Deposited TiO 2 films changes with ion energy. Moreover TiO 2 and Ta 2 O 5 layers deposited by conventional evaporation present reversible disturbances of their optical properties when illuminated with high power flux. A model taking into account both thermal and nonlinear properties (localized optical Kerr type effect) of the prism coupler system is used to explain the measurements and to estimate the nonlinear refractive index coefficient of different thin films.