Waveguide holograms in thin dichromated gelatin films

Thin dichromated gelatin films were used to record waveguide holograms directly inside the film. Information was stored and retrieved by light of the same wavelength. The waveguides were characterized by optical attenuation < 1 dB/cm and this value was retained after the film sensitization, exposure, and development cycle, so that holograms could be recorded. Sinusoidal gratings were formed and these were used to couple radiation into thin-film waveguides and also as waveguide Fourier holograms of two-dimensional images. The efficiency of a sinusoidal grating as a coupling component was 60%. A Fourier hologram reconstructed by the waveguide method with a diffraction efficiency of 11% was characterized by a recorded data density of ~ 10⁵ bit/ mm² over an area of 1 mm².