Holographic Volume Gratings in Dye-Doped Jelly-Like Gelatin

Holographic characteristics of a thick self-developing photosensitive medium - dye-doped jelly-like gelatin are investigated by means of pulsed laser exposure. The experiments were performed using aqueous gelatin solutions of Rhodamin 6G with a layer thickness of 1 mm. The slanted holographic gratings were written with two crossed beams from a frequency-doubled (λ = 532 nm) and Q-switched YAG:Nd laser (τ 0.5 ≈ 17 ns, f ≤ 50 Hz). In the course of recording the hologram was read with the beam from a single-mode He-Ne laser (λ = 632.8 nm) which was not absorbed by the photosensitive medium. The real-time evolution of the grating diffraction efficiency was studied in dependence of the dye and gelatin concentration as well as the writing pulse fluence. It is shown that under appropriate choice of the medium composition and parameters of the recording radiation, it is possible to obtain phase volume holographic gratings with a diffraction efficiency of ~ 87 % and an angular selectivity of ~ 20'.