Spatially selective harmonic transmission in a nonlinear plasma-inspired oscillator chain with asymmetric coupling

We investigate the spatial transmission and spectral redistribution of a periodically forced one-dimensional chain of nonlinear oscillators with asymmetric nearest-neighbor coupling. The external forcing is applied only to the first oscillator, while the remaining units are excited through the coupling interaction. The directional coupling coefficients, ϵ 1 and ϵ 2 , are used to control the balance between forward and backward interactions. Numerical simulations show that reciprocal coupling produces strong spatial attenuation of the fundamental response, whereas asymmetric coupling gives rise to distinct transmission regimes, including attenuated, efficient, re-entrant, and strongly suppressed propagation. Two-parameter response maps further show that the region supporting appreciable fundamental transmission becomes progressively narrower with propagation distance, indicating an increasing sensitivity to the directional coupling balance. In addition, the oscillator nonlinearity transfers energy from the forcing frequency to its higher harmonics. Their spatial evolution can differ substantially from that of the fundamental component. In particular, for a representative asymmetric coupling, the fundamental response becomes strongly attenuated while the fifth harmonic grows and subsequently persists over the remaining part of the chain. Thus, suppression of the externally imposed frequency does not necessarily imply suppression of the total oscillatory response. These results demonstrate that asymmetric coupling can simultaneously control spatial transmission and spectral redistribution in nonlinear oscillator chains.