The zero dispersion wavelength (ZDW) of existing optical fibers is relatively large; thus, it cannot be matched easily with those of most commercial lasers. Additionally, owing to their complex structure and manufacturing challenges, these fibers exhibit significant losses, thus necessitating improvements to the fabrication process. Therefore, optimizing the fiber structure to achieve a further blue shift in the ZDW while maintaining a broad infrared transmission band and wide supercontinuum spectrum (SC) has become the key focus in chalcogenide fiber research. In this study, As-S and As-Se-Te glasses were selected as materials for suspended-core fibers. Notably, Te-based chalcogenide glass can significantly enhance the mid-to-far infrared transmission, thus significantly extending the infrared long-wave cutoff. Because of its highly nonlinear effect, Te-based glass can generate a wide SC. This type of fiber provides critical technological support for future high-energy outputs in mid-to-far infrared lasers and for new wide-spectrum sensing applications.

By designing a novel Te-based suspended-core optical fiber, we first measured the material dispersion and waveguide dispersion of glass to verify the ability of the fiber to adjust the ZDW. Next, we numerically investigated the dispersion of the designed suspended-core fiber and a conventional core-cladding fiber to predict the advantages of the suspended-core fiber with small core diameters in dispersion control. Subsequently, two types of infrared glass materials were prepared, and their refractive indices and glass transition temperature (T_g) were tested. The fiber preform was fabricated via an isolated extrusion method; subsequently, fiber drawing and loss measurements were performed. Finally, the generalized nonlinear Schrodinger equation (GNLSE) was used to simulate the SC of the fiber and determine its maximum spectral width and flatness.

The fiber designed in this study exhibits a superior ZDW compared with conventional core-cladding fibers with small core diameters. The simulation results show that as the core diameter decreases, the dispersion blue shift becomes more pronounced. When the core diameter is less than 6.5 μm, the blue shift of the ZDW in the suspended-core fiber is significantly faster than that in the conventional step-index fiber structure (Fig. 2). Additionally, the width of the support structure affects the fiber dispersion; the wider the support, the more significant is the ZDW red shift (Fig. 3). The glass materials used for fiber drawing were As₃S₇ and As₃₀Se₅₀Te₂₀, which have significantly different refractive indices [Fig. 5(a)] but similar T_g values [Fig. 5(b)]. The measured substrate loss of the unclad fiber and the single-point loss of the suspended-core fiber at 4.7 μm are shown in (Fig. 6). The broadest SC was obtained at a pump wavelength of 2.38 μm, with a spectral bandwidth ranging from 1.14 μm to 10.16 μm (Fig. 7). Furthermore, as the pump wavelength increases, the short-wavelength cutoff of the SC redshifts gradually and the flatness decreases significantly.

This paper presents the design for a mid-infrared Te-based chalcogenide suspended-core fiber. To further optimize the structure, the fundamental-mode dispersion was simulated under various core diameters and bridge widths, and the results were compared with those of material dispersion. The waveguide dispersion of the fiber is superior to the material dispersion. Additionally, the ZDW of the designed suspended-core fiber is significantly better than that of conventional core-cladding structures with small core diameters (less than 6.5 μm). Meanwhile, the bridge width significantly affects the dispersion characteristics of the fiber. The fabrication of As₃S₇ glass and As₃₀Se₅₀Te₂₀ glass are reported herein, along with the measurements of their refractive indices and thermal properties, including the T_g. Furthermore, a suspended-core fiber preform was fabricated using the isolated extrusion method, and a four-hole suspended-core fiber with an As₃₀Se₅₀Te₂₀ core was drawn. Based on measurement, the overall average loss of the fiber is 3.54 dB/m, with a loss of 7.06 dB/m at a laser calibration wavelength of 4.7 μm. Additionally, simulations of SC generation at different pump wavelengths were performed. The broadest SC, with a spectral bandwidth of 1.14 μm to 10.16 μm, was obtained at a pump wavelength of 2.38 μm under a laser intensity of -30 dB.