Chalcogenide integrated hollow-core optical fibers for infrared light guidance
The low-loss light transmission and broad bandwidth of hollow-core negative curvature fibers (NCFs) have a variety of applications in infrared (IR) light guidance, such as chemical detection, biomedical surgery, and laser delivery. Although silica is a material of choice for light guidance in the visible and near-IR spectra, transmission losses increase drastically in the mid-IR region; thus, other mid-IR transparent materials, such as chalcogenide glasses, are potentially preferred to guide the light. In this thesis, various cladding designs of arsenic trisulfide (As2S3) and arsenic triselenide (As2Se3) chalcogenide NCFs are numerically explored for low-loss transmission in the mid-IR region. A detailed numerical investigation in the optimization of As2S3 NCFs with tubular and elliptical cladding elements was performed, and a low-loss ellipse-nested tubular NCF design is proposed for mid-IR guidance. The effect on the transmission loss due to cladding elements of the proposed low-loss As2Se3 ellipse-nested tubular fiber design was investigated. Confinement and total loss of all fiber designs were numerically studied, and the single-mode light guidance performance of the proposed low-loss fiber design was explored. The bending loss performance of the fiber was analyzed in the targeted spectrum, and a dispersion control study was carried out to investigate the effect of the primary design parameters on the dispersion performance. A fabrication tolerance study was performed to investigate the effects of common fabrication issues on the proposed design’s guidance properties. In the second part of the thesis, NCFs with silica, chalcogenide, and chalcogenide-coated silica cladding elements were numerically investigated for low-loss near and mid-IR transmission. As2S3 coated silica NCF was compared to simple silica and simple As2S3 fiber to understand the effect of the As2S3 coating on the transmission loss of silica NCF. Fabrication of silica NCF through the stack-and-draw technique followed by micro-coating with As2S3 solution was performed to improve the transmission performance of the As2S3 coated silica glass-based NCF. Further modifications in the fabrication of the NCFs were realized for a thorough comparison with the numerical investigations.