Browsing by Author "Khan, Asfandyar"

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Open Access
Chalcogenide integrated hollow-core optical fibers for infrared light guidance
(2022-12) Khan, Asfandyar
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.
Open Access
Exploration of hybrid cladding elements in chalcogenide hollow-core fibers for low-loss mid-infrared transmission
(Elsevier GmbH, 2021-10-27) Khan, Asfandyar; Ordu, Mustafa
Optical losses of chalcogenide negative curvature hollow-core fibers with hybrid cladding elements were numerically investigated in this study. Microstructured cladding formed by the combination of tubular and elliptical elements was designed for low-loss operation in the mid-infrared spectrum. A confinement loss value of 0.287 dB/km was calculated for the proposed ellipse-nested tubular negative curvature fiber with optimized design parameters at 10.6 µm. Achieved confinement losses with the proposed design are several orders of magnitude lower than the tubular/elliptical negative curvature fibers in the targeted spectrum. The effect of the material absorption to the total fiber losses was also investigated along with the confinement losses. Suppression on the higher-order modes by the proposed fiber was numerically observed. The negative curvature fibers are promising for the low-loss guidance of CO2 lasers that are widely used for various applications spanning from material processing to surgery.
Open Access
Mid-infrared negative curvature hollow-core fiber with elliptically nested tubular structure
(Elsevier B.V., 2022-12-24) Khan, Asfandyar; Ordu, Mustafa
Arsenic triselenide chalcogenide negative curvature hollow-core fiber with ellipse-nested tubular cladding elements was numerically presented for the low-loss light guidance in the mid-infrared region. Confinement and total losses were calculated for the fiber with a five-tube design as low as 0.34 dB/km and 4.55 dB/km at 10.6μm, respectively. The single-mode light guidance characteristic of the proposed design was investigated, and a strong suppression on the higher-order modes shows that the fiber design favors the light guidance with the fundamental mode. A dispersion control study was carried out to optimize the primary design parameters to shift the zero-dispersion wavelength close to 10.6μm. The bending loss performance of the proposed design was analyzed in the targeted spectrum. The proposed negative curvature hollow-core fiber could be potentially used in low-loss guidance for high-power lasers and could also be utilized for several other applications, such as surgery and drug delivery in the mid-IR spectrum. © 2022 Elsevier B.V.