All-optical analogue of anti-skyrmions and anti-merons in difference-frequency-generation process
In the paraxial domain, a difference-frequency generation (DFG) process provides a versatile platform for exploring non-Hermitian dynamics in an all-classical interaction. This letter aims to show the existence of topologically non-trivial optical analogues of anti-Skyrmionic states in an 'anti' parity-time (anti-PT) symmetry-broken dynamical interaction in a DFG process. A practical DFG set-up, which is constituted by a periodically-poled lithium tantalate (PPLT) crystal and pumped by a visible (green) pump laser, is considered for ascertaining the non-Hermitian dynamics. In the anti-PT symmetry broken phase, a negatively phase-mismatched interaction gives rise to a topologically non-trivial pseudo-magnetization texture that could support anti-skyrmion-like quasi-particles in signal and idler modes. The analysis also reveals the existence of anti-meron like pseudo-magnetization texture for a phase-matched DFG.