Abstract
The advent of the ‘lab-on-fiber’ concept has boosted the prosperity of optical fiber-based platforms integrated with nanostructured metasurface technology which are capable of controlling the light at the nanoscale for multifunctional applications. Here, we propose an endless single-mode large-mode-area photonic crystal fiber (LMA-PCF) integrated metalens for broadband and efficient focusing from 800 to 1550 nm. In the present work, the optical properties of the substrate LMA-PCF were investigated, and the metalens, consisting of dielectric TiO2 nanorods with varying radii, was elaborately designed in the fiber core region with a diameter of 48 μm to cover the required phase profile for efficient focusing with a high transmission. The focusing characteristics of the designed metalens were also investigated in detail over a wide wavelength range. It is shown that the in-fiber metalens is capable of converging the incident beams into the bright, symmetric, and legible focal spots with a large focal length of 315–380 μm depending on the operating wavelength. A high and average focusing efficiency of 70% was also obtained with varying wavelengths. It is believed the proposed fiber metalens may show great potential in applications including fiber laser configuration, machining, and fiber communication.
Highlights
Since the first demonstration of silica optical fiber with a low transmission loss of20 dB/km in the early 1970s [1], low-loss optical fibers have revolutionized the telecommunication industry in the last five decades and have continued to evolve toward an extremely low level with a value of 0.14 dB/km at 1550 nm [2]
We propose an endless single-mode photonic crystal fiber (PCF) integrated metalens which operates in a broadband wavelength range from 800 to 1550 nm
The numerical simulation was carried out using the finite difference time domain (FDTD) method, and the incident light is assumed to propagate along the +z of 12 axis
Summary
Since the first demonstration of silica optical fiber with a low transmission loss of. 20 dB/km in the early 1970s [1], low-loss optical fibers have revolutionized the telecommunication industry in the last five decades and have continued to evolve toward an extremely low level with a value of 0.14 dB/km at 1550 nm [2]. Various types of optical fibers have been developed and serve as a well-established platform for efficient light guiding and transmission. A large number of applications based on optical fiber technology have been realized, such as optical sensing for various physical parameters [3,4], fiber lasers and amplifiers [5,6], and astrophysics [7]. Despite the tremendous success of optical fiber technology, there exist some drawbacks hindering the widespread application of optical fibers. The transmitted modes in the fiber core tend to diverge which are restricted by the diffraction limit of the core size
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