A. Sharma, M. Dokhanian, A. Kassu, A. Parikh, Optics Letters 30, 501-503, 2005

Holographic gratings are recorded in azo-dye nitrobenzoxazole-labeled phospholipid thin films by use of 244-nm UV light. The gratings continue to grow for more than 1 h, even after the recording light is removed. The diffraction efficiency of these gratings shows extreme sensitivity to humidity and can increase reversibly by 2 orders of magnitude in air that is saturated with water vapor. This effect is related to the unique characteristics of phospholipid molecules that undergo hydration-dependent structural reorganization and self-assembly.