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

Abstract

This paper presents the results of a study of the refractive-index dispersion for the AgBr–TlI, AgBr–TiBr_0.46I_0.54, and AgCl–AgBr crystal systems in the spectral range from 0.4 to 56 µm, 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 µm 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 µm. Inserts with diameter 16 µm 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 µm 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±30µm. The fibers were suitable for transporting both laser and thermal radiation from heated objects to a thermal viewer.