Photonic Band Effects on the Optical Nonlinearities of a:SiN_x-Based 1D Photonic Architectures

Meticulously engineered nonstoichiometric a:SiN_x-based photonic structures, such as optical microcavities, facilitate the emergence of pronounced photonic states that are predominantly influenced by defect and interface energies, resulting in diverse and complex electron-photon interactions. In this study, we present third-order nonlinear optical investigations on a:SiN_x-based optical microcavities employing femtosecond lasers across a broad wavelength range of 740-900 nm to examine the effects associated with photonic band edges, which are contingent upon defect and interface energies. The dispersion of nonlinear absorption (β) and the nonlinear refractive index (n₂) through wavelength- and angle-dependent studies strongly correlate with linear angular photonic mode dispersion. Intensity-dependent nonlinear assessments provide a variation of impact with the photonic band edge effects. The strong optical field confinements and layer-by-layer nonlinearities show substantial effects on the effective optical nonlinearities in the spectral domain. Such a significant impact of photonic modes and the marked dependence of the nonlinear optical properties on optical microcavity structures highlight promising avenues for designing various photonic interconnects suited for both linear and nonlinear optical applications.