Efficient harmonic generation in an adiabatic multimode submicron tapered optical fiber

Abstract Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. While previously demonstrated applications relied exclusively on the low-loss transmission of only fundamental mode, implementation multimode tapers that adiabatically transmit several modes has remained very challenging, hindering their use in various emerging nonlinear optics and quantum optics. Here, we report realization submicron permit simultaneous adiabatic multiple higher-order including LP 02 through introducing deep wet-etching conventional fiber before tapering. Furthermore, a critical application, demonstrate fundamental-to-fundamental all-fiber third-harmonic generation with high conversion efficiencies. Our work paves way ultrahigh-efficiency optics, facilitating nonclassical light regime, soliton interactions photonic gates, manipulation evanescent-field-induced trapping potentials atoms nanoparticles.