Panchromatic recording of nanocomposite holographic gratings with large refractive index modulation amplitudes

A photopolymerizable nanoparticle-polymer composite (NPC) is a novel nanocomposite photopolymer that is dispersed with inorganic nanoparticles having a large refractive-index difference from that of the formed polymer. In order to realize the uniform and high dispersion of nanoparticles without any aggregation, we employ nanostructured polymers that possess highly branched main chains, the so-called hyperbranched polymer (HBP), as size and refractive-index controllable organic nanoparticles with its ultrahigh refractive index. We show that high dispersion of the ultrahigh refractive index HBP in a photopolymerizable NPC provides a volume holographic grating possessing the saturated refractive modulation amplitude as large as 0.03 at grating spacing of 0.5-mu m in all the visible spectral regions of the red (640nm), the green (532nm) and the blue (405nm). Such a high contrast volume holographic grating can be used for volume optical holographic elements in a wearable headset for augmented and mixed reality.