Snake—Modulation Dynamics of an Optical—Terahertz Soliton in a Graded-Index Waveguide

A nonlinear stage of the effect of snake and modulation instabilities on the dynamics of an optical—terahertz soliton in a quadratically nonlinear graded-index waveguide has been studied theoretically. It has been shown that both instabilities are of fundamental importance and cannot be separated from each other. If the carrier frequency of the optical component is in the region of an anomalous dispersion of the group velocity, these instabilities are developed in a blow-up regime, leading to the self-focusing of the soliton. In the case of the normal dispersion of the group velocity, the mutual effect of the waveguide and snake—modulation dynamics results in the formation of a stable spatiotemporal soliton.