Influence of nonic nonlinearity on spatiotemporal modulational instabilities in PT-symmetric fiber Bragg grating structures

This study investigates the impact of cubic-nonic (CN) nonlinearity on the instability of Parity-Time (PT) symmetric fiber Bragg grating structures in different PT-symmetry regimes. By employing linear stability analysis, we calculate the amplification factor of modulational instability (MI) and examine the impact of cubic-nonic nonlinearities on the lower and upper limits of the photonic band gaps. The results of our study indicate that the presence of CN nonlinearity significantly affects the amount of reciprocal information gained. By modifying the cubic and nonic nonlinearities under various PT-symmetric situations, we may proficiently control MI. This examination reveals several types of spectra, such as asymmetry, symmetry, sideband spectrum, constantly increasing gain, and broad spectrum. We are witnessing atypical spectra that display discrete and isolated data points instead of a continuous and uninterrupted pattern. In addition, we investigate the generation of solitary waves in nonlinear episodic structures while considering PT symmetry. These observations have possible consequences for creating sophisticated optical devices and systems, where managing nonlinear dynamics is essential for telecommunications and photonic signal processing applications.