Red sensitivity of dichromated gelatin films

Dichromated gelatin films present sensitivity to red light without any special sensitization. This sensitivity is due to an absorption appearing in dichromated gelatin films and attributed mainly to a charge–transfer transition which results in an electron transfer from gelatin to chromium. To characterize holographically this recording material, both reflection and transmission gratings have been obtained using the 632.8-nm radiation from a He–Ne laser.