Single-Mode Segmented Cladding Fibers for the Middle Infrared

Single-mode (SM) fibers for the middle infrared (3-20 mum) are required for a variety of purposes, such as spatial filtering and interferometry. There has only been limited success in the development of such fibers, due to the lack of suitable materials that transmit in this spectral range. In this paper, we report the design and fabrication of SM segmented cladding fibers made of silver halide materials. The fiber design consists of a uniform core of high-refractive material that is surrounded by a cladding of alternating segments of high and low refractive indices. These fibers can maintain a SM operation over a wide spectral range with a very large core area.