Fig. 4: Numerical front propagation in a bistable optical chain with nonreciprocal coupling model Eq. (3) with η = 0.5, μ = 2.2, D = 0.6, \({\kappa }_{+}=0.1+3{\alpha }^{{\prime} }\), \({\kappa }_{-}=0.1-3{\alpha }^{{\prime} }\), and \({\alpha }^{{\prime} }\) is the bifurcation parameter.
From: Nonlinear wave propagation in a bistable optical chain with nonreciprocal coupling
a Front profile for different nonreciprocal couplings. Panels a1, a2, and a3 show front propagation towards the left, symmetrical, and right flank, respectively. b Spatiotemporal diagram of the respective fronts. Panels b1–b6 account for direct simulations and the nonreciprocal bistable system chain reconstruction. Fronts speed towards the left and right flank as a function of the nonreciprocal parameter \({\alpha }^{{\prime} }\). Panels c, d account for small and large nonreciprocal coupling, respectively. The blue and red curves show the front speed towards the right (VR) and left (VL) flank, respectively. The system exhibits a pinning-depinning transition of front nonlinear waves for \({\alpha }^{{\prime} }={\alpha }_{pd}^{\pm }\). \({\alpha }_{m}^{\pm }\) accounts for the critical value for the nonreciprocal coupling parameter with the greatest magnitude observed for the front speed.
