Nonlinear optical fullerene and graphene-based polymeric 1D photonic crystals: Perspectives for slow and fast optical bistability

Nonlinear optical (NLO) properties of materials can be enhanced by assembling them as thin polymer composite films alternating with other polymers and forming dielectric mirrors, 1D photonic crystals (1DPCs), wherein the input light intensity is increased. Based on the poly(vinyl carbazole) (PVK) and poly(vinyl alcohol) (PVA) contrasting polymer pair, variants of such structures, with graphene and fullerene in their high-index layers, have been produced. Their optical switching characteristics have been studied with ns, cw, and quasi-cw fs laser sources in the IR and with a fs laser in the visible range. We have demonstrated slow optical bistability in the polymeric 1DPCs determined by the thermal expansion of polymer composites at intensities over 100 W/cm² as well as fast and ultrafast optical switching due to thermo-optic and Kerr nonlinearities, respectively. Characteristic nonlinear refractive coefficients responsible for these processes were found to be n^to₂ ∼ 10⁻¹ cm²/GW and n^Kerr₂ ∼ 10⁻⁴ cm²/GW. A subpicosecond fast spectral shift of the 1DPC bandgap has been found. Our results and analysis provide a clear picture of the NLO behavior of 1DPCs at different time scales. The results stimulate the subsequent design of ultrafast switches and bistable memory cells based on polymeric 1DPCs whose micrometer thickness and flexibility offer promise for implementation into fiber and microchip configurations.