Nonlinear Metafiber: Unlocking Novel Pathway for Ultrafast Supercontinuum Generation in Small-Core Suspended Core Fibers

Supercontinuum generation (SCG) using ultrashort pulses in microstructured optical fibers enables broadband spectral distribution [1]. Suspended core fibers (SCFs), with their micron-scale cores, are ideal for ultrafast nonlinear frequency conversion [2]. However, their small cores result in poor and unstable coupling efficiency, requiring complex free-space optics. This limits SCFs to laboratory use, highlighting the need for integrated solutions. To address this, we introduced the first demonstration of nonlinear metafibers, simplifying efficient light coupling into small cores. Using 3D nanoprinting approach, we combined a dispersion-engineered SCF with a phase-only metalens to focus plane waves onto the SCF core, enabling nearly alignment-free, robust coupling of broadband ultrashort pulses. This approach eliminates the need for bulky optics, enabling efficient excitation of the fundamental fiber mode and facilitating soliton-based SCG in a compact device.