Study on Four-Wave Mixing Enhancement in Nanofiber Systems

We investigate four-wave mixing (FWM) in a five-level atomic system coupled to an optical nanofiber. The transverse inhomogeneity of the guided field is incorporated through a mode-weighted mean-field approximation, yielding effective one-dimensional propagation equations. The conversion efficiency is evaluated over different detuning parameters and compared with a uniform-field reference under consistent normalization. For the parameters studied, the nanofiber model predicts higher peak conversion efficiencies, accompanied by distinct changes in the spectral response. The two-photon resonance narrows, the upper-transition resonance retains nearly the same bandwidth, and the range of probe detunings supporting appreciable conversion broadens. To account for the interplay among detuning parameters, particle swarm optimization (PSO) is employed, yielding a best-found efficiency of 1.85×10−3 within the prescribed search bounds. The resulting two-dimensional efficiency map exhibits a tilted high-efficiency band, revealing a correlated dependence on the detunings rather than independently optimized resonances. These findings clarify how transverse mode confinement and coupled detuning conditions shape the spectral response of FWM in the nanofiber–atom system.