Microstructured single-mode IR fibers based on metal halides with increased mode-field diameter

This paper presents the results of a study of the refractive-index dispersion for the AgBr-TlI, AgBr-TiBr0.46I0.54, and AgCl-AgBr crystal systems in the spectral range from 0.4 to 56 mu m, along with the results of the development and fabrication of single-mode microstructured IR fibers by extrusion from solid solutions of metal halides. The fibers had a central insert 16 mu m in diameter of composition 2.6 mol% TlI in AgBr, located in a matrix of composition 2.3 mol% TlI in AgBr with external diameter 525 mu m. Inserts with diameter 16 mu m of composition 2.0 mol% TlI in AgB were placed in the matrix in hexagonal order. The distribution of the radiation emitted from the fibers in the far field at wavelength 10.6 mu m was studied, along with the influence of local heating of a section of the fiber on the transport of the IR radiation. The mode-field diameter was experimentally estimated as 120 +/- 30 mu m. The fibers were suitable for transporting both laser and thermal radiation from heated objects to a thermal viewer. (C) 2021 Optical Society of America