Photonic crystal fiber metalens

Jingyi Yang,Din Ping Tsai,Pin Chieh Wu,Ho Wai Howard Lee,Sudip Gurung,Catherine Arndt,Indra Ghimire

doi:10.1515/nanoph-2018-0204

Abstract

Abstract Conventional optical fiber has excellent performance in guiding light, which has been widely employed for long-distance optical communication. Although the optical fiber is efficient for transmitting light, its functionality is limited by the dielectric properties of the core’s and cladding’s materials (e.g. Ge-doped-silica and silica glasses). The spot size of the transmitted light is diverging and restricted by the diffraction limit of the dielectric core, and the numerical aperture is determined by the refractive index of the fiber materials. However, the novel technology of metasurfaces is opening the door to a variety of optical fiber innovations. Here, we report an ultrathin optical metalens directly patterned on the facet of a photonic crystal optical fiber that enables light focusing in the telecommunication regime. In-fiber metalenses with focal lengths of 28 μm and 40 μm at a wavelength of 1550 nm are demonstrated with maximum enhanced optical intensity as large as 234%. The ultrathin optical fiber metalens may find novel applications in optical imaging, sensing, and fiber laser designs.

Highlights

Optical fiber is a well-established efficient platform used to guide light and allow high bandwidth optical transmission for long-distance communication with low attenuation
These in-fiber plasmonic lenses with concentric annular slits suffer from relatively short focal length (
We developed the first optical fiber metalens with engineerable focal length by directly patterning a geometric phase (i.e. Berry phase) altering metasurface onto the end facet of a large-mode-area photonic crystal fiber (LMAPCF)

Summary

Introduction

Optical fiber is a well-established efficient platform used to guide light and allow high bandwidth optical transmission for long-distance communication with low attenuation. Attempts have been made to fabricate periodical plasmonic nanostructures (i.e. slits, holes, bars, etc.) on the optical fiber facets to alter the optical properties and to extend the functionalities of the fibers, as elements of these plasmonic nanostructures can interact directly with well-guided modes of the optical fiber. Realization of an in-fiber focusing lens via plasmonic nanostructures has been studied in recent years [17,18,19]. These in-fiber plasmonic lenses with concentric annular slits suffer from relatively short focal length (

Methods

Results

Conclusion