NEW METHOD FOR DETERMINING REFRACTIVE-INDEX AND THICKNESS OF FLUORESCENT THIN-FILMS

The optical parameters of homogeneous, isotropic, and fluorescent thin films are determined by comparing measured with calculated angular intensity distributions of the s- and p-polarized light emitted into the substrate. The method also yields information about the multipole nature of the emitted radiation. The theory is presented for electric and magnetic dipole transitions. For extremely thin layers of optical thickness n0d0 ≪ λ/8 (where λ is the emission wavelength) analytic expressions for the angular intensity distributions are given. For between 25-30 nm thick evaporated layers of an europium-benzoyltrifluoro-acetone- chelate the refractive index was determined to be n0 = 1.57 at λ = 612 nm. The fluorescent light emitted by these layers in an about 6 nm wide band centered at λ = 612 nm is emitted by randomly oriented electric dipoles. © 1979.