Nanograting-Enhanced Optical Fibers for Visible and Infrared Light Collection at Large Input Angles

Ning Wang,Matthias Zeisberger,Markus A. Schmidt,Uwe Hübner

doi:10.3390/photonics8080295

Ning Wang, Matthias Zeisberger + Show 2 more

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https://doi.org/10.3390/photonics8080295

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Abstract

The efficient incoupling of light into particular fibers at large angles is essential for a multitude of applications; however, this is difficult to achieve with commonly used fibers due to low numerical aperture. Here, we demonstrate that commonly used optical fibers functionalized with arrays of metallic nanodots show substantially improved large-angle light-collection performances at multiple wavelengths. In particular, we show that at visible wavelengths, higher diffraction orders contribute significantly to the light-coupling efficiency, independent of the incident polarization, with a dominant excitation of the fundamental mode. The experimental observation is confirmed by an analytical model, which directly suggests further improvement in incoupling efficiency through the use of powerful nanostructures such as metasurface or dielectric gratings. Therefore, our concept paves the way for high-performance fiber-based optical devices and is particularly relevant within the context of endoscopic-type applications in life science and light collection within quantum technology.

Highlights

Even though optical fibers have been used to great success in a multitude of areas, collecting light under large angles within different spectral regimes remains a key challenge with commonly used fibers due to low numerical aperture
We demonstrate in this work that optical fibers functionalized with arrays of metallic nanodots located on the core of the fiber substantially improve light-collection performance at multiple wavelengths, extending the spectral domain of operation towards the visible
1650 nm), while nanostructure implementation relies on modified electron beam lithography

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. (SMF-28) is only 0.14 at λ = 1550 nm), the light collection efficiency of commonly used step-index fibers is insufficient for many applications and cannot satisfy the demands of emerging applications such as wide-field endoscopes [11] or quantum photon probes [12]. To address this challenge, we have recently introduced a universal approach for improving the light-incoupling ability of optical fibers through integrating plasmonic nanodot arrays [13] and dielectric concentric rings [14] on end faces of SMF-28.

Theoretical Toy Model Analysis

Implementation and Characterization Setup

Experimental Results

Conclusions