10 W-Level, All-Fiber Supercontinuum Generation From Visible to Mid-Infrared by Broadband Laser Beam Combination in GeO₂-Core Fiber

GeO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>-core fibers (GCFs) exhibit higher optical nonlinearity and superior mid-infrared (MIR) transmission properties compared to silica fibers. They also demonstrate greater durability in high-power MIR applications than fluoride fibers, making them ideal for high-brightness, broadband supercontinuum (SC) generation in the visible to MIR region. However, the ZDWs of GCFs are located around 1.6 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m, unable to match well with the common fiber laser wavelengths (e.g., 1.03 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m, 1.55 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m, 2.0 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m), limiting the SC bandwidth. Specifically, pumping GCFs at 1.55 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m with a nanosecond laser can produce SC with good spectral properties in the visible to near-infrared (NIR) region, but its long-wavelength edge (LWE) extends to MIR region is difficult; conversely, although pumping at the 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m band, the spectral LWE can extend beyond 3.5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m, its short-wavelength edge (SWE) is limited to around 1.9 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m. To combine the strengths of these approaches and generate SC covering both visible and MIR regions, we, for the first time, present a broadband SC laser beam combination in a custom-made high-power GCF-based tapered fiber bundle (H-GTFB). The resultant SC covers a spectral range of 0.7–3.5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i>m with a maximum average power exceeding 9 W. Moreover, the power fluctuation root mean square (RMS) value was measured to be approximately 0.261% at an average power of 9.12 W over 2.5 hours. These findings significantly contribute to the advancement of high-power, broadband, fiberized SC sources.