Hologram formation with red light in methylene blue sensitized dichromated gelatin

The spectral sensitization of hardened dichromated gelatin to red light is carried out using methylene blue as sensitizer. The sensitized dichromated gelatin plate can be stored for over 1 month in an ammonia atmosphere without loss of photosensitivity. Holograms recorded in the sensitized dichromated gelatin using a He-Ne laser have high diffraction efficiency and low noise if they are swelled at a temperature near the gelatin gel melting point during development processing. Maximum diffraction efficiency has been found to be as high as 88%. The energy required to obtain 80% diffraction efficiency is 150-400 mJ/cm(2).