Pure quartic modulational instability in weakly nonlocal birefringent fibers

The modulational instability (MI) phenomenon is theoretically investigated in birefringent optical media with pure quartic dispersion and weak Kerr nonlocal nonlinearity. We find from the MI gain that instability regions are more expanded due to nonlocality, which is confirmed via direct numerical simulations showing the emergence of Akhmediev breathers (ABs) in the total energy context. In addition, the balanced competition between nonlocality and other nonlinear and dispersive effects exclusively gives the possibility of generating long-lived structures which deepens our understanding of soliton dynamics in pure-quartic dispersive optical systems and opens new investigation routes in fields related to nonlinear optics and lasers.