20.6 W Mid-Infrared Supercontinuum Generation in ZBLAN Fiber With Spectrum of 1.9–4.3 μm

Abstract

A 20.6-W mid-infrared supercontinuum (MIR-SC) generation is demonstrated in a piece of step-index ZBLAN (ZrF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -AlF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -NaF) fiber. A silica-fiber-based SC laser operating at 1.9-2.6 μm is used as a pump source. Owing to the specially designed ZBLAN fiber which perfectly matches the pigtail of the pump source in mode-field-diameter, direct fusion splicing was achieved between the ZBLAN fiber and the pigtail of the pump source instead of being connected via a piece of transition fiber. The coupling loss of the fusion splicing joint between the silica fiber and the ZBLAN fiber was measured as 0.26 dB@2000 nm. Robust fiber endcap made of multimode AlF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> fiber also benefited high-power MIR-SC generation. Spectral and power characteristics of the generated SC under different pump pulse duration and pulse repetition rate were carefully studied. A 20.6-W SC was obtained with an overall spectral coverage and a 10-dB long wavelength edge of 1.92-4.29 μm and 4.08 μm, respectively. This is, to the best of the authors' knowledge, the first demonstration of 20-W level SC laser based on ZBLAN fiber with long wavelength edge extending beyond 4 μm.