Nonlinear optical performance of periodic structures made from composites of polymers and Co₃ O₄ nanoparticles

The nonlinear optical performance of specially designed periodic structures made from composites of optical polymers and Co₃ O₄ nanoparticles is investigated. The refractive indices of the alternating layers are designed to be close and no photonic band gap (PBG) is formed at low power density. Under high power illumination, the index difference becomes large because of the high optical nonlinearities of the Co₃ O₄ nanoparticles. Consequently, enhanced nonlinear optical performance is obtained with the formation and the strengthening of the PBG. Nonlinear reflection and nonlinear transmission as well as reduced nonlinear threshold are observed in the PBG structures.