We describe an experimental investigation of volume holographic recording in photopolymerizable thiol-ene based nanoparticle-polymer composites (NPCs) at a wavelength of 404 nm. We introduce a new photoinitiator, Irgacure819, for efficient volume holographic recording in the blue-violet spectral region and measure the photopolymerization dynamics and the holographic recording properties at its varying concentrations. It is found that doping of 0.1 wt.% Irgacure 819 provides the saturated refractive index modulation amplitude as large as 9.5×10<sup>−3</sup> and the material recording sensitiviey as high as 1800 cm/J. These measured values are much larger than the minimum required values for holographic data storage media. It is also shown that the out-of-plane shrinkage can be suppressed more with decreasing the photoinitiator concentration. We compare these results with another blue sensitizer, Darocur TPO, to evaluate the performance of Irgacure 819.
We report on volume holographic recording in thiol-ene based nanoparticle-polymer composites (NPCs) at a wavelength of 404 nm by using a highly coherent blue diode laser. We study the photopolymerization dynamics of two types of thiol-ene based NPCs doped with different blue-sensitive initiator/sensitizer systems (Darocur ® TPO and Irgacure ® 784/BzO<sub>2</sub>) at various doping concentrations. We also characterize a volume holographic grating recorded in these two types of thiol-ene based NPCs. Such material characterization includes the refractive index modulation, the material recording sensitivity and polymerization shrinkage. It is shown that Darocur R _ TPO provides larger refractive index modulation and higher material recording sensitivity than those with Irgacure ® 784/BzO<sub>2</sub> but these two blue-sensitive initiator/sensitizer systems amount to meeting the requirements of the refractive index modulation and the material recording sensitivity for holographic data storage. However, it is found that shrinkage reduction of a volume grating recorded in these two types of thiol-ene based NPCs at 404 nm is not as effective as the same thiol-ene based NPC doped with Irgacure ® 784/BzO<sub>2</sub> at 532 nm.