Slow-Photon Modes Mediated Enhanced Nonlinear Optical Absorption of a Fluorophenyl Porphyrin in a Flexible All-Polymer Bragg Reflector

Most of the nonlinear optical (NLO) materials explored so far seem to be impractical for direct use in all-optical information processing since they demand high operational power to obtain an appreciable NLO signal. Integrating optical nonlinearity with nanophotonic architectures can resolve the issue by greatly reducing the threshold input power levels and thus can unveil new pathways in realizing all-optical devices suitable for next-generation photonics technology. In this work, we report the enhanced NLO activity of 5,15-di­(pyridyl)-10,20-bis­(pentafluorophenyl)­porphyrin, abbreviated as PFP, by using an all-polymer nonlinear Bragg reflector. Polymeric Bragg reflectors have recently been found to be more beneficial than conventional inorganic systems toward future on-chip photonics technology, but considerable efforts are required while handling them. We used a spin-casted Bragg reflector and took advantage of the slow light effects occurring at the photonic band edges to achieve a ∼3-fold enhancement in the NLO response of PFP. The influence of nonlinear refraction on the nonlinear absorption of PFP within the Bragg structure was also analyzed. The optical power limiting studies revealed an excellent limiting behavior with a limiting threshold value as low as 0.66 J/cm2 at the input laser intensity of 0.27 GW/cm2 with the Bragg reflector. These results suggest the potential of our system in developing simple, cost-effective, all-optical devices that can operate at low input power levels.