Fremgangsmåte for fremstilling av et hologram med höy virkningsgrad samt hologram fremstilt ved fremgangsmåten

Light sensitive recording medium is exposed to highly absorbed incoherent light either before or after a slant fringe hologram is recorded therein to reduce the sensitivity of the medium at surface regions adjacent a supporting substrate. The fringes recorded in the area of reduced sensitivity have lower contrast than those recorded in the remainder of the medium, freeing the fringes from the substrate and allowing greater expansion of the medium during a subsequent chemical swelling process. The increased swelling amplifies the refractive index modulation in the medium to increase the diffraction efficiency of the hologram. Dye may be added to the medium to increase absorbance of the incoherent light.