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Synthesis and Design of Zinc Selenide and Multi-Material Optical Fibers for High Power Mid-Infrared Applications

Author
Hendrickson, Alexander T.
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2020.
Physical Description
1 electronic document
Additional Creators
Asbury, John B.
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Open Access.
Summary
Optical fibers with mid-infrared capabilities and active fiber properties will make up the next generation of optical fiber technology. For this to happen, fibers must be made with crystalline or semiconductor materials or must take advantage of increasingly complex photonic bandgap structures. Here, zinc selenide fibers and multi-material Bragg fibers are described with the intention of eventually creating a high power mid-infrared tunable laser. Zinc selenide cannot be readily synthesized into a fiber geometry over long lengths because its high vapor pressure at elevated temperatures makes it incompatible with fiber drawing techniques. To overcome this challenge, high pressure chemical vapor deposition has been designed so that zinc selenide may be deposited directly into hollow silica optical fiber claddings. These zinc selenide optical fibers have low losses, 1 dB/cm or less, and may be doped with transition metal dopants to bring forward active mid-infrared functionality. In particular, Cr2+ and Fe2+ dopants allow for tunable mid-infrared fiber lasers. Two major challenges for moving these fiber lasers to viability are discussed. The first is that the high pressure chemical vapor deposition process which is used to synthesize them leaves behind a central pore that negatively affects the mode structure of the fiber and fiber laser; the second is that zinc selenide's high thermo-optic coefficient causes detrimental effects when it is optically pumped with high powers. Both challenges are addressed. To remove the central pore both chemical vapor transport may be performed, utilizing the silica cladding as a micro-ampoule. Laser annealing may also collapse the pore by locally heating the zinc selenide core. To facilitate passive laser cooling, conductive cladding materials are proposed. Polycrystalline silicon and diamond are synthesized as cladding materials because of their high thermal conductivities and infrared compatibility. For silicon to be used as a cladding material, photonic bandgap fibers with silicon and germanium Bragg reflectors were synthesized. Zinc selenide can be infiltrated into the core of these fibers, giving them photonic bandgap properties, which may, in the future, be used to modify the lasing characteristics of doped fiber lasers. These advanced fiber post-processing techniques and cladding designs improve the diversity of next-generation optical fibers. By improving mode quality and power handling, high power mid-infrared optical fibers are one step closer to maturity.
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Dissertation Note
Ph.D. Pennsylvania State University 2020.
Reproduction Note
Microfilm (positive). 1 reel ; 35 mm. (University Microfilms 28778378)
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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