Features of recording holograms in polymethylmethacrylate doped by boron difluoride anthraceneacetonates

Holographic gratings formation in polymethylmethacrylate doped with boron difluoride anthraceneacetonates was studied. It was shown, that the time dependence of refractive index (RI) modulation amplitude for recorded holographic gratings demonstrates M-shaped character, with the first (up to 0.5 × 10⁻⁴ RI units) and the second (up to 0.2 × 10⁻⁴ RI units) maxima of this dependence being caused by photodimerizability and postexposure diffusion of photoactive additive molecules. It was found that the material's resolution determined by competition of diffusion and photochemical processes for recorded gratings is about 1000 lines/mm. However, due to diffusion this value raises with time after the recording process end reaching 2500 lines/mm. It was shown that the optimal exposure time is inversely proportional to the grating spatial frequency and can be reduced by more than an order of magnitude by material heating from 25 °C to 75 °C.