Quantitative refractive index analysis of thermal and non-thermal curing of polymeric holographic material

Abstract

Recent volume holographic recording materials commonly include a thermal curing step. There are attempts to directly cure liquid resin into a grating with lower success. This study explores the use of a viscous dimethacrylate resin as a holographic recording material synthesized both with and without thermal polymerization. We conducted a quantitative analysis of the refractive index modulation (Δn) in these materials utilizing two distinct holographic setups. The non-thermally polymerized films exhibited a lower Δn value of 0.27×10-3, which continued to increase with rising photoinitiator concentrations as the polymer matrix remained incompletely formed. Additionally, we observed distinct trends in Δn evolution with respect to exposure time and photoinitiator concentration. These findings emphasize the notable differences in Δn behavior between thermally and non-thermally polymerized materials, suggesting that the latter shows potential for further optimization by mitigating diffusion and stability effects.