Photoinduction of spontaneous surface relief gratings on Azo DR1 glass

Surface relief gratings were spontaneously photoinduced from a collimated Nd:YAG laser beam at 532 nm on thin films of a disperse red 1 functionalized glass-forming compound. Pattern formation was studied by measuring the diffraction intensity of a He-Ne laser probe beam at 633 nm and by atomic force microscopy (AFM). The dependence of pattern formation on both irradiation time and intensity was studied. The gratings could be erased both optically and thermally. The orientation of the gratings is influenced by the polarization of the writing beam, and it is accompanied by strong diffraction of the incident light into the sample plane, thereby providing a way to couple and trap the light into the substrate. Interestingly, photobleaching upon prolonged irradiation yields transparent gratings, and the process is partially reversible upon thermal erasure.