The Formation of Volume Transmission Gratings in Acrylamide-Based Photopolymers Using Curcumin as a Long-Wavelength Photosensitizer

Abstract

Curcumin, a natural dye found in the Curcuma longa rhizome, commonly called turmeric, is used as a photosensitizer in acrylamide-based photopolymers for holographic data storage. We studied the absorbance of photopolymer films that show two absorption bands due to curcumin, acrylamide monomer (AA), and the crosslinking agent N,N′-methylenebisacrylamide (MBA). Analysis of the real-time diffraction efficiency of these films shows a maximum of 16% for the sample with the highest curcumin concentration. Moreover, increasing the curcumin load enhanced the refractive index contrast from 7.8 × 10−4 for the photopolymer with the lowest curcumin load to 1.1 × 10−3 for the photopolymer with the largest load. The sensitivity and diffraction efficiency of the recorded gratings also increased from 7.0 to 9.8 cm·J−1 and from 7.9 to 16% with the increase in curcumin load, respectively. Finally, the influence of NaOH on the photopolymerization of the AA-curcumin-based sample shows a diffraction efficiency increase with the NaOH content, revealing that the curcumin enol form is more efficient as a photosensitizer.

The Interplay of Processing-Related Influences on the Formation of Volume Holographic Gratings in a Free-Surface Epoxy-Based Recording Material

“…New materials for volume holography are constantly being developed and researched more and more intensively [2,11]. New compositions, e.g., focusing on biodegradable components [12] or hydrogels [13], or new photosensitizers based on natural dye [14], are being explored, while increasing the sensitivity and diffraction efficiency of the recorded gratings. The key to exploring and optimizing volume holographic materials for various applications is their design and understanding of the underlying grating formation processes [15].…”