A W-Type Double-Cladding IR Fiber With Ultra-High Numerical Aperture

We have prepared a novel fiber consisting of three different glasses with W-type double-cladding structure and constant core-to-cladding ratio by the extrusion method. An ultra-high numerical aperture (NA ≥ 2.17) indicates that this fiber has a good capability of collecting and confining light in a wide wavelength range. The lowest fiber loss is approximately 1.7 dB/m at 6.1 μm. Supercontinuum spectrum covering 1.6 μm to 10.85 μm at a bandwidth of -30 dB has been demonstrated in a 21 cm long fiber pumped by 5 μm laser. This chalcogenide fiber has high-NA and W-type double-cladding structure, and thus shows great potentials in the field of high power laser delivery, high efficiency imaging and high-capacity signal transmission in the mid-infrared.