Hybrid Plasmonic Coupled Nanophotonic Cavity-Mediated Tunable Nonlinear Absorption in Cobalt Phthalocyanine

Abstract

Light–matter interaction in subwavelength-scale optical confinement structures is a hot topic in basic science and the photonic industry. Materials experiencing high electric field strength can change their optical properties according to the intensity of light, as governed by the laws of nonlinear optics. In this paper, we investigate the linear and nonlinear optical behavior of cobalt phthalocyanine (CoPc) placed in the combined local fields of plasmonic and photonic cavity modes. Using polymeric layers, we created a planar microcavity and embedded the cavity layer with CoPc/Au nanocomposites. The enormous field strengths caused by the cavity photon–plasmon coupling significantly enhance the nonlinear optical absorption of the CoPc. The combination of photon–plasmon–exciton interactions in the hybrid microcavity results in an enhancement of the excited-state absorption of the system, even at low excitation intensities. The degree of light coupling can be altered by tuning the angle of light incidence, thereby varying the nonlinear transmittance of the microcavity structure. The proposed system can act as an angle-tunable nonlinear optical switch that works for laser pulses, with high attenuation at normal incidence and high transmittance at oblique incidence. Our findings provide a comprehensive understanding of the resonant light–matter interactions in tailored photonic crystal structures and how these interactions nonlinearly alter the optical properties, with potential for use in photonic applications.