Photonic band-edge assisted enhanced nonlinear absorption of carbon encapsulated gold nanostructures in polymeric multilayers

Abstract

Integration of nonlinear optical materials in nanophotonic structures offers unprecedented opportunities to tailor the light-matter interaction, resulting in tunable optical responses. Periodic dielectric structures are particularly the desired optical platform to incorporate nonlinear materials to enhance their weak nonlinearity for practical applications. In this work, we report the giant enhancement in the nonlinear absorption of a 1-D polymer photonic crystal containing gold-carbon (Au@C) core–shell structure. The Au@C nanostructures synthesized by pulsed laser ablation technique were dispersed in spin-coated alternate layers of photonic crystal comprised of polyvinyl carbazole and cellulose acetate. The long-wavelength photonic band-edge of the polymeric Bragg mirror was designed at 532 nm to enhance the non-resonant nonlinear absorption of the core–shell nanostructure. The resultant nonlinearity is ascribed to slow light propagation at the band-edges and consequent local field confinement of optical pulses. Angle-dependent tunability of photonic band-edge effects and nonlinear transmission characteristics were analyzed experimentally and correlated with numerical simulations. These findings open up new ways to implement cost-effective, highly tunable and low input threshold all-optical devices.