Jeļena Miķelsone defend PhD thesis "Holographic recording and surface relief formation in azobenzene compounds"

In this thesis optical holographic recording in functional polymers, low-weight molecular organic glasses, “guest-host” system was studied. Diffractive optical elements (DOE) fabrication possibilities were investigated. DOE fabrication is important for many industries because they can be used in telecommunications, monochromators, electrooptical devices, optical filters production, in art, security systems, etc. Advantages of obtained gratings is cheap materials for synthesis, easy synthesis, no post-purifying of material is required. Enhancement of photosensitivity and surface relief grating self-enhancement process was studied. It allows decreasing energy required for surface relief grating recording. In this thesis different material where studied and compared: functional polymers where photosensitive azocompound is covalently attached to the main polymeric chain; azobenzene containing low-weight molecular organic glasses; “guest-host” system – polymer and azocompound mixture. Recording parameters influence on surface relief formation was studied; surface relief formation mechanism was suggested. Indirect method for mass movement direction determination in surface relief grating was described. Surface relief grating physical self-enhancement method was studied. Thesis:

1. Mass transport direction can be obtained indirectly, by investigating changes in diffraction efficiency monotonicity during holographic recording.
2. Mass transport during surface relief grating formation occurs in the materials possessing photoinduced birefringence phenomena.
3. Azo-epoxy AAB:BADGE compound is a promising material for direct holographic recording due to easy synthesis and good photosensitivity.