Azopolymer materials for optical recording Institute of Applied Physics Academy of Sciences of Moldova Chisinau, Moldova Azopolymer materials for optical recording Losmanschii Constantin

Schematic cross-section of photoresponsive surface

Polymer materials for photonics The development of photonics technology is crucially dependent on the availability of suitable optical materials. Polymer materials with photosensitive properties are emerging as an important class of materials for a variety of photonics applications.

Light and polymer interaction

Photosensitivity of polymers PEPC CHI3 photochrome AZO-dye

Inorganic photoresist Thermal vacuum evaporation The procedure of hologram producing involves the main steps as: Obtaining of recording media Recording of hologram, chemical processing Multiplication of holograms. Now as recording media the company use inorganic recording medium that is coated on substrate by thermal vacuum evaporation. Inorganic photoresist Thermal vacuum evaporation 500-600ºC, 3000 W Inorganic thin film

Carbazole-containing polymer materials attract wide interest due to their applications in optical data storage and information processing. The host carbazole-containing polymer possesses good photorefractive, photoconductive, and photochemical properties for hologram recording. Holographic gratings obtaining on carbazole materials involves exposure of the thin film to an interference pattern. Two coupling gratings are formed simultaneously during the holographic recording: phase grating, due to the refractive index changes and amplitude grating, resulting from the changes of absorption coefficient. After exposure the surface relief grating is developed by a wet chemical process leads to film thickness changes. A.Andriesh et al. Application of carbazole-containing polymer materials as recording media, Phys Status Solidi A. 208, 1837 (2011)

Recently polymer materials with azo dyes become attractive materials for holographic recording due to possibility of surface relief grating fabrication. It has been reported that large surface modulations can be obtained on azo polymer films upon exposure to an interference pattern of laser beams. By virtue of their photochemical isomerization between trans- and cis-forms, azopolymers have proven to be ideal for creating a vast array of photonics elements. Kim et al. was the first group reporting the surface relief grating on polymer films. The reorientation of the azobenzene group induces the large scale molecular motion, and results in the mass transport of the irradiated azopolymer thin film. Kim et al. Laser‐induced holographic surface relief gratings on nonlinear optical polymer films, Appl. Phys. Lett. 66, 1166 (1995)

Structure of EPC:DO (90:10). The aim of the work was the synthesis and characterization of new carbazole-based azopolymer suitable for direct surface relief grating formation. Carbazole-based polymer Epoxypropylcarbazole (EPC) and azodye Disperse Orange was utilized in this study. 9-(2,3-epoxypropyl)carbazole Structure of EPC:DO (90:10). Disperse Orange 3 (Sigma-Aldrich)

The EPC:DO polymer was soluble in common organic solvents and formed good optical quality films by spin coating. Polymer thin films were prepared by spin coating the filtered 10 wt.% polymer solution in toluene onto glass substrate. These films were dried in oven at 60°C for 6 hours. The thickness of films was about 270 nm. A schematic model describing the film formation during the spin-coating process. After the initial spin-off stage (i), where solvent is evaporated (ii), the thin film is formed (iii).

Recording setup

SRG amplitude is about 48% of the film thickness AFM surface profile and three-dimensional view of the grating on the polymer film. Recording configuration: 532 nm, RCP:LCP h=130 nm d=270 nm K=h/d=48% SRG amplitude is about 48% of the film thickness

Comparison of recording media obtaining Thermal vacuum evaporation 500-600ºC, 3000W Spin-coating Room temperature, 700 rpm Inorganic photoresist Inorganic thin film Organic photoresist Organic thin film

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