Mid-infrared supercontinuum generation in soft-glass specialty optical fibers: A review

Mid-infrared region (2-20 μm) is an important region of electromagnetic spectrum. Most of the molecules including CH₄, CO, NO, NO₂, C₆H₆, TNT, NH₃, SF₆, HNO₃, greenhouse gas radiation etc. have their fundamental vibrations in this domain. Thus, the mid-infrared region is known as 'molecular fingerprint region' and desirable to get the signature of these molecules. Tellurite and chalcogenide glasses have the advantages of a wide transparency window (up to ~20 μm) and very high optical nonlinearities, making them decent candidates for the mid-infrared supercontinuum generation. Photonic crystal fibers provide the wavelength-scale periodic arrangement of microstructure along their length. The core of the photonic crystal fibers and two-dimensional photonic crystal based on diverse geometries and the materials, permitting supercontinuum generation due to various nonlinear effects in an enormously broad spectral range. In this review paper, we report the recent developments in the field of mid-infrared supercontinuum generation in both the tellurite and chalcogenide glass state-of-the-art optical fibers. Particular attention is paid to the mid-infrared supercontinuum generation in the step-index, suspended-core, tapered, and photonic crystal fibers or microstructured optical fibers in tellurite and chalcogenide glasses. The coherence property of mid-infrared supercontinuum generation in all-normal dispersion engineered specialty optical fibers is also reviewed.