Beyond Two-Octave Supercontinuum Generation for OAM Modes in Fluoride Fiber

Orbital angular momentum (OAM) has attracted significant research interest due to its unique phase properties. Supercontinuum generation based on OAM mode offers the potential to broaden the spectrum and enable new applications. While silica-based optical fibers have been successful in OAM supercontinuum generation, their strong absorption limits their use in the mid-infrared (> 2500 nm) region. Fluoride glasses have been investigated as an alternative for supercontinuum generation, which could extend the corresponding spectrum to the mid-infrared wavelength range. In this work, we propose a ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) ring-core fiber (RCF) for OAM modes supercontinuum generation. After adjusting the structural parameters, the OAM1,1mode exhibits a flat dispersion distribution from 1500 nm to 5000 nm, with a1,1mode can be generated with a spectral broadening from 863 nm to 4980 nm, with > 0.99 coherence at -40 dB power. Furthermore, after using the same short-wavelength pulses with 1900 nm and 1550 nm incident wavelengths, the spectrum of OAM2,1mode can be extended to a broadband supercontinuum from 780 nm to 3520 nm after 1.1 cm of transmission, whereas the maximum spectral broadening of the OAM3,1mode (580 nm to 2620 nm) is reached after only 0.7 cm of transmission, with more than 2-octave and the coherence is > 0.99 in all cases.