OPTIMIZATION OF TETRAGONAL KTA1-XNBXO3-FE CRYSTALS AS STORAGE MATERIALS FOR DOUBLE-EXPOSURE HOLOGRAPHIC-INTERFEROMETRY

Double-exposure holographic interferometry with as-grown and oxidized iron-doped tetragonal potassium tantalate-niobate (KTN:Fe) crystals as a photorefractive storage material is presented. The influence of oxidation treatments on the light-induced refractive index change and decay time constant is investigated for different external electric fields and spatial frequencies. The experimental findings can be explained in terms of a charge transport model which assumes one kind of photorefractive centres with hole conductivity only. The fringe contrast and exposure time of double-exposure holographic interferograms are determined. The displacement of a test target is evaluated from interferograms utilizing a quasi-heterodyne technique. For that purpose a fully automatically working computer program is developed.