Photonic Crystal Fiber Metalens

TL;DR

This paper presents an ultrathin metalens integrated with optical fiber that focuses light efficiently at telecommunication wavelengths, enabling advanced in-fiber optical devices for imaging, sensing, and laser applications.

Contribution

It introduces a novel in-fiber metalens with specific focal lengths and efficiency, demonstrating a new approach to manipulate light within optical fibers.

Findings

Achieved focal lengths of 28 and 40 micrometers.

Maximum efficiency of approximately 16.4% at 1550 nm.

Successful integration of metalens on fiber facet.

Abstract

Optical fiber is a well-established efficient way to guide and manipulate light and allowing high bandwidth optical transmission for long distance communication with low attenuation. Although a dielectric optical waveguide is efficient for transmitting light, its functionality is limited by the dielectric properties of the materials of core and cladding.The light coming out from optical fiber is typically diverging, and the numerical aperture is determined by the refractive index of the fiber materials. Thus, the light intensity decreases significantly upon exiting the fiber. The use of metasurfaces provides the opportunity to tailor light properties for advanced light manipulation and to develop novel optical applications that are flat. By producing a specific phase profile using spatially-varied nano-antenna elements, metasurfaces can control the wavefront of the transmitted, reflected, and scattered light, and enable novel ultrathin optical components such as flat lenses. Here, we report an ultrathin optical metalens cascaded on the facet of optical fiber that enables light focusing in the telecommunication regime. In-fiber metalenses with focal lengths of 28 and 40 um and maximum efficiency of ~16.4% at a wavelength of 1550 nm are demonstrated. The integration of an ultrathin metalens and optical fiber will open the path to revolutionary in-fiber optical devices for practical applications in optical imaging, sensing, and fiber laser.