High numerical aperture large-core photonic crystal fiber for a broadband infrared transmission

In this paper we present a large mode area photonic crystal fiber made of the heavy metal oxide glass CS-740, dedicated for a broadband light guidance in the visible, near- and mid-infrared regions of wavelengths from 0.4 to 4.7 mu m. The fiber is effectively multi-mode in the considered wavelength range. It is composed of a ring of air-holes surrounding the core, with a high linear filling factor of 0.97. The fiber was made using a standard stack-and-draw technique. Each hole has a size of approx. 2.5 x 3.0 mu m and diameter of core is 80 mu m. Fiber attenuation is below 3 dB/m in the 0.9-1.7 tm wavelength range, while at 4.4 mu m (mid-IR) it is approx. 5 dB/cm. Bending loss at the 1.55 mu m wavelength is 0.45 dB per loop of 8 mm radius. Fiber numerical aperture is 0.53 at 1.55 mu m. The effective mode area of the fundamental mode is approx. 2400 mu m(2) in the wavelength range of 0.8-1.7 mu m. We present a proof-of-concept demonstration that our large core photonic crystal fiber is able to efficiently collect light directly from a mid-IR quantum cascade laser without use of additional optics and can be used for pigtailing mid-IR sources and detectors. (C) 2016 Elsevier B.V. All rights reserved.