Holographic recording in [Sb(PO3)3]n–Sb2O3 glassy films by photoinduced volume and refraction index changes

Abstract

Glassy films of 0.2[Sb(PO3)3]n–0.8Sb2O3 with 0.8μm-thickness were deposited on quartz substrates by electron beam evaporation. A contraction in the film thickness (photoinduced decrease in volume) and photobleaching effect associated with a decrease of up to 25% in the index of refraction has been observed in the films after irradiation near the bandgap (3.89eV), using the 350.7nm (3.54eV) Kr+ ion laser line with 2.5W/cm2 for 30min. A loss of 30% in the phosphorus concentration was measured by wavelength dispersive X-ray microanalysis in the film after laser irradiation with 5.0W/cm2 for 1.0h. These photoinduced changes in the samples are dependent on the power density and intensity profile of the laser beam. Using a Lloyd’s mirror setup for continuous wave holography it was possible to record holographic gratings with period from 500nm up to 20μm and depth profile of ∼50nm in the films after laser irradiation with 5.0W/cm2 for 1h. Real-time diffraction efficiency measurements have shown that ultraviolet irradiation induces first a refractive index grating formation, and after this, the photocontraction effect takes place generating an irreversible relief grating. Diffraction efficiency up to 10% was achieved for the recorded gratings. 3D-refraction index measurements and atomic force microscopy images are presented.