Modeling of dispersion-engineered all-chalcogenide step-index fiber for wideband supercontinuum generation in the mid-infrared

摘要

Mid-infrared region supercontinuum (SC) generation through designing broadband light sources recently attracts considerable attention in the field of nonlinear optics owing to their numerous applications in sensing and biological imaging. Broadband light sources designed based on different waveguiding structures adopted until today, the SC generation using optical step-index fiber is the prominent one due to its design and fabrication flexibility. In this study, a promising 5-cm-long SC source has been designed and modeled using a step-index fiber structure employing highly nonlinear chalcogenide (ChG) materials such as As_2Se_3 glass as a core and Ge_(11.5) As_(24)Se_(64.5) glass for its outer cladding. Fiber structure is suitably modeled through its group-velocity dispersion optimization by varying core diameter. The optimized fiber structures are excited using a pump source having 170-fs pulses at 5.5 μm with a peak power of 10 kW. Initial all-normal dispersion excitation produces SC broadening up to 9.5 μm. Further study in a new optimization shows that spectral evolution can be expanded beyond 17 μm covering the wavelength from 3.2 to beyond 17 μm if the fiber structure is excited in the anomalous dispersion regime through a suitably tailored flat group-velocity dispersion curve with smaller in magnitude over a wide wavelength range. Such a promising SC source, which is designed based on typical step-index fiber principle using highly nonlinear ChG glass system, can be utilized in a variety of mid-infrared region applications.