Biphoton holographic storage in Methyl Orange and Ethyl Orange dyes

Biphoton holograms are recorded by a He-Ne laser in Methyl Orange and Ethyl Orange dyes on exposure to a 514.5-nm argon-ion laser, and the dynamic of holographic recording is reported. The recording utilizes an unusual photochemistry that is due to either to a triplet-triplet transition from a long-lived triplet lower state of the cis configuration or a transition back to the trans state.