Integratable high-efficiency achromatic metalens across the entire low-loss bands of optical fiber from 1260 to 1625  nm

A challenge in optic fiber is to control dispersion over the entire low-loss bands covering the O + E + S + C + L bands with integratable ultracompact devices, which inevitably limits the range of fiber-based applications. Metalens supplies a dynamic platform for correcting chromatic aberration of optical devices in a flexible, integratable, and ultracompact way. Hence, we propose a broadband achromatic metalens integrated on the end face of a single-mode fiber covering the entire low-loss wavelength region. Utilizing the particle swarm optimization algorithm, we have substantially mitigated the phase-compensated matching error in the achromatic scheme. It demonstrates that the metalens is achievable with achromatic aberration and focuses over the entire low-loss wavelength band with a high mean focusing efficiency of 84.55%. Furthermore, this device exhibits a remarkable capability to break through the diffraction limit of the output field. This work provides a theoretical basis for fiber-integrated achromatic metalens over the entire low-loss bands, which has promising applications in imaging, sensing, and optical communication.