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MESHALKIN, Alexei; LOSHMANSKY, Constantin; CAZAC, Veronica; ABASHKIN, Vladimir; ACHIMOVA, Elena. Recording of superimposed relief gratings on carbazole-based azopolymer. In: Materials Science and Condensed Matter Physics. Ediția a 9-a, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, p. 297.
|Materials Science and Condensed Matter Physics
Ediția a 9-a, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 25-28 septembrie 2018
A carbazole-based azopolymer Polyepoxypropilcarbazole:Disperse Orange was used as recording media for holographic grating recording. Exposure by interference pattern of laser beam (473 nm, 1700 mW/cm2) showed ability to direct form surface relief gratings. Due to this property, superimposed surface relief structures were fabricated on the obtained thin azopolymer films by using the dual-beam multiple exposure technique. The superimposed gratings with 1-, 2- and 3-fold rotation symmetry were successfully photofabricated by direct recording without any etching. For inscribing surface-relief-grating, a linearly polarized beam from a DPSS laser was used as the light source. The s-polarized laser beam was split into two equal-intensity beams by using a beam splitter. Two λ/2 wave plates were used to provide the best polarizations configuration p-p for effective surface relief formation. A azopolymer film mounted on a rotation stage was exposed to the interference pattern for a fixed period of time. After each exposure, the sample was rotated around the surface normal to achieve the required orientation of the grating vector relative to the previous one. To fabricate a superimposed structure with n-fold rotation symmetry, the rotation angle was π/n and n exposure steps were required. The time period for each exposure was constant and equal to 5 min. The profiles and depths of the recorded superimposed gratings were detected by digital holographic microscopy (DHM) and atomic-force microscopy (AFM). In Fig. 1 (a, b, c) the obtained by DHM images of the superimposed gratings of 1-, 2- and 3-fold rotation symmetry are shown. AFM image with rectangular regular relief structures of superimposed grating recorded through 2 exposure steps and its diffraction pattern is shown in Fig. 2. The modulation depth of the pattern is 1200 nm estimated from the AFM cross-section profile. The surface profile shows linear, rectangular and hexagonal surface pattern for the 1-, 2- and 3-fold rotation symmetry gratings.