Effect of Photonic Cavity Interactions on Femtosecond Multiphoton Optical Nonlinear Absorptions from Bi₂O₃-Based One-Dimensional Photonic Crystal

Abstract

The photonic cavity-mediated precise control of femtosecond optical nonlinearity of several orders of magnitude enhancement is demonstrated in a novel nonlinear one-dimensional (1D) photonic crystal. The demonstrated photonic structure contains a highly nonlinear metal oxide, Bi2O3 as a central defect layer within two SiO2/TiO2 distributed Bragg reflectors. The nonlinear optical interactions of the electronic states of Bi2O3 with the cavity mode and adjacent photonic minibands are closely monitored by femtosecond Gaussian laser beam propagation over a wide-range of spectral wavelengths, 350–1600 nm. Abnormal cross-over from positive (reverse saturation) nonlinear absorption (RSA, β = (+)12 × 10–10 m W–1) to negative (saturation) nonlinear absorption (SA, β = (−) 11× 10–10 m W–1) is witnessed when the confined optical fields are strongly coupled to the excitation laser and mid-band gap energies of Bi2O3, during effective cavity length tuning. The femtosecond laser pulse propagation at different wavelengths effectively probed the multiphoton-induced optical nonlinearities, which are distinctly different from low- and high-energy minibands compared to the cavity resonance and are manifold-enhanced relative to pristine Bi2O3. The photonic mode density-dependent pronounced two-/multiphoton absorptions are systematically analyzed with experiments and simulations. The novel photonic architecture can be utilized in optical switches, optical limiters, and ultrafast photonic device applications.