Study of refractive index modifications and of thermal properties of optical thin films with the prism coupler

摘要

The prism coupler can be used with a single beam to measure the refractive indices of isotropic or anisotropic single layers and of layers in multilayer stacks with an accuracy of 1.x10~-3. The refractive index modification with temperature can also be measured easily. The refractive index of a thin film can also change under illumination. A two-beam set-up has been developed to acheive a very high sensitivity of 1.x10~-6 on the refractive index changes. The nonlinear response of the layer's materials is mainly deu to thermal effects. As well the diffusion length of the effect as the frequency response are measured even for low absorbing thin films. Examples of measurements are given. The heat equations permit to calculate the temperature distribution in the whole system to that both theoretical and experimental means can now be used to determine thermal properties of materials in thin film form.