HIGH PRESSURE SYNTHESIS OF IN-SITU DOPED CR2+ ZINC SELENIDE FIBER LASERS
Open Access
- Author:
- Krug, James
- Graduate Program:
- Chemistry
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 07, 2019
- Committee Members:
- John V Badding, Thesis Advisor/Co-Advisor
Miriam Arak Freedman, Committee Member
Lauren Dell Zarzar, Committee Member
Venkatraman Gopalan, Committee Member - Keywords:
- zinc selenide
fiber laser
Cr2+ - Abstract:
- The integration of optically active semiconductor crystalline materials into amorphous optical fibers is promising development towards the creation of new solid state fiber lasers. Deposition into glass capillaries with large aspect ratios is possible by using the novel technique of high pressure chemical vapor deposition which produces conformal annular films of crystalline material over centimeters of length. A strong candidate for lasing media is the zinc chalcogenide II-VI compound semiconductor ZnSe doped with Cr2+. ZnSe is optically transparent in the infrared, often used as an optical window or lens for CO2 lasers. Addition of a transition metal creates a gain medium with a large emission cross section between 2-3µm which overlaps with the fingerprint region of many organic molecules, enabling infrared characterization techniques. Transition metal dopants such as Cr2+ also emit in the region used to pump Fe2+:ZnSe gain media. Beyond material properties, the fiber geometry allows easy use with a variety of coupling arrangements as well as being compact and rugged for moving systems. In addition to broad application use, the fiber geometry offers a radial symmetry capable of dissipating heat in 360° which can help overcome thermal issues typically encountered at higher powers in bulk lasers. The research conducted in this thesis looks to further improve in-situ Cr2+ doping and to identify and analyze the fiber laser’s capabilities. As a result of the vapor deposition of Zn and Se precursors, an inner pore forms in the deposited film. Incorporation into other template materials and post processing are investigated to develop methods to remove the central pore. Additionally, a wide parameter space was explored with the aim to better understand and control high pressure chemical vapor deposition. Measurements of loss and waveguiding experiments were conducted to evaluate the detrimental effects of the pore as a hindrance to power scaling in the system. As a result, it was determined that the fibers are able to handle large pump powers, power scaling of the fiber laser is limited by loss from the pore and removal of the inner pore requires an expansion matched template with a high glass transition temperature.