2016/02/16 by Saeid Biria, Philip P. A. Malley, Tara F. Kahan +1 · 3 citations
Engineering · Physics and Astronomy · #Nonlinear Optical Materials Studies #Photonic Crystals and Applications #Photorefractive and Nonlinear Optics
paper · doi:10.1021/acs.jpcc.5b11377
openalex publication_date 2016/02/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/07
We report cross-link-tunable, nonlinear optical pattern formation of transmitted light in a photopolymer undergoing free-radical polymerization. Photopolymerization induces microscale filamentation of a uniform, broad transmitted beam, which corresponds to a concurrent spatial evolution in cross-linked morphology in the photopolymer. Because the photopolymerization is permanent, the ensemble of filaments imprint a microstructure comprising a cross-link gradient pattern. Tuning the system’s capability to cross-link and branch changes the magnitude of the refractive index change (Δ n ), which both induces nonlinear conditions and also changes the strength of the optical nonlinearity. Only a monomer with sufficient functionality shows stable optical pattern formation, and its nonlinear regime exists for a specific range of exposure intensities. A monomer of lower functionality can be pushed into the nonlinear regime by formulating it with higher functional monomers, whereby Δ n is increased to provide a stronger response to light. In such formulations, the strength of the nonlinearity, as evidenced by changes in light confinement in the optical pattern, is tuned by varying this monomer’s functionality or its relative weight fraction. The strong correlation among polymerization-induced refractive index change, optical pattern feature size, and cross-linked morphology demonstrates tunable optical nonlinearity through variations in the inherent polymer structure.