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PublisherThe University of Arizona.
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AbstractMid-infrared (IR) lasers (2-12 μm) have found tremendous applications in medical surgeries, spectroscopy, remote sensing, etc. Nowadays, mid-IR emissions are usually generated from semiconductor lasers, gas lasers, and solid-state lasers based on nonlinear wavelength conversion. However, they usually have disadvantages including poor beam quality, low efficiency, and complicated configurations. Mid-IR fiber lasers have the advantages of excellent beam quality, high efficiency, inherent simplicity, compactness, and outstanding heat-dissipating capability, and have attracted significant interest in recent years. In this dissertation, I have studied and investigated Q-switched and mode-locked fiber lasers in the mid-IR wavelength region. My dissertation includes six chapters: In Chapter 1, I review the background of mid-IR lasers and address my motivation on the research of mid-IR fiber lasers; In Chapter 2, I present the experimental results of microsecond and nanosecond Er³⁺-doped and Ho³⁺-doped fiber lasers in the 3 μm wavelength region Q-switched by Fe²⁺:ZnSe and graphene saturable absorbers. In Chapter 3, Q-switched 3 μm laser fiber amplifiers are investigated experimentally and theoretically and their power scaling are discussed. In Chapter 4, a graphene mode-locked Er³⁺-doped fiber lasers at 2.8 μm with a pulse width < 50 ps is presented. In Chapter 5, extending the spectral range of mid-IR fiber lasers by use of nonlinear wavelength conversion is addressed and discussed. I have proposed 10-watt-level 3-5 μm Raman lasers using tellurite fibers as the nonlinear gain medium and pumped by our Er³⁺-doped fiber lasers at 2.8 μm. In the last chapter, the prospect of mid-IR fiber laser is addressed and further research work is discussed.
Degree ProgramGraduate College
Degree GrantorUniversity of Arizona
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Dye laser and diode laser spectroscopy of gas phase free radicals.Bernath, Peter F.; Bopegedera, A. M. Ranjika Priyadarshi.; Rund, John V.; Enemark, John H.; Smith, Mark A.; Barfield, Michael A. (The University of Arizona., 1989)The gaseous free radicals, alkaline-earth metal monoalkylamides, monoacetylides, monoformamidates and monopyrrolidates, consisting of a metal atom (Ca or Sr) bonded to a single ligand, were synthesized in a Broida oven. The electronic and vibrational structures of these molecules were studied by low-resolution laser spectroscopy techniques. These inorganic molecules are ionic, well represented by the structure M⁺L⁻ (M = Ca, Sr: L = ligand). Three electronic transitions were identified for the metal monoalkylamides and the metal monoformamidates. The formamidate anion bonds to the metal in a bidentate fashion through the oxygen and nitrogen atoms. Two electronic transitions were observed for the metal monopyrrolidates. The pyrrolide anion ring bonds to the metal to provide these "open-faced sandwich" type molecules with pseudo-C₅ᵥ symmetry. For the metal monoacetylide molecules, only one electronic transition (Ā²Π-Ẋ²Σ⁺) was observed. Several vibrational frequencies were determined for these inorganic molecules from the low-resolution spectra. The Ā²Π-Ẋ²Σ⁺ transition of the calcium monoacetylide molecule was rotationally analyzed at high-resolution using the filtered laser excitation spectoscopy technique. The rotational line positions were fitted to a ²Π-²Σ⁺ Hamiltonian to obtain several rotational constants. The calcium-carbon bond length in CaCCH was calculated for the ground (2.248 Å) and excited (2.200 Å) electronic states. The vibration-rotation spectra of the gaseous bismuth hydride and bismuth deuteride molecules were recorded, using a diode laser system. The 1-0 fundamental band and several hot bands with Δv-1 were rotationally analyzed. The rotational line positions were fitted first, to a Dunham energy expression and then to a ³Σ⁻ Hamiltonian, to obtain ground state rotational constants. The bismuth-hydrogen (deuterium) bond distance was calculated to be 1.809 Å (1.807 Å).
5 kW Near-Diffraction-Limited and 8 kW High-Brightness Monolithic Continuous Wave Fiber Lasers Directly Pumped by Laser DiodesFang, Qiang; Li, Jinhui; Shi, Wei; Qin, Yuguo; Xu, Yang; Meng, Xiangjie; Norwood, Robert A.; Peyghambarian, Nasser; Univ Arizona, Coll Opt Sci (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017-10)Tandem pumping technique are traditionally adopted to develop > 3-kW continuous-wave (cw) Yb3+-doped fiber lasers, which are usually pumped by other fiber lasers at shorter wavelengths (1018 nm e.g.). Fiber lasers directly pumped by laser diodes have higher wall-plug efficiency and are more compact. Here we report two high brightness monolithic cw fiber laser sources at 1080 nm. Both lasers consist of a cw fiber laser oscillator and one laser-diode pumped double cladding fiber amplifier in the master oscillator-power amplifier configuration. One laser, using 30-mu m-core Yb3+-doped fiber as the gain medium, can produce > 5-kW average laser power with near diffraction-limited beam quality (M-2<1.8). The slope efficiency of the fiber amplifier with respect to the launched pump power reached 86.5%. The other laser utilized 50-mu m-core Yb3+-doped fiber as the gain medium and produced > 8-kW average laser power with high beam quality (M-2: similar to 4). The slope efficiency of the fiber amplifier with respect to the launched pump power reach 83%. To the best of our knowledge, this is the first detailed report for > 5-kW near-diffraction-limited and > 8-kW high-brightness monolithic fiber lasers directly pumped by laser diodes.
Thulium Doped Microsphere Laser and Fiber LaserPeyghambarian, Nassser N.; Wu, Jianfeng; Peyghambarian, Nassser N.; Kost, Alan; Jiang, Shibin (The University of Arizona., 2005)In this dissertation, the spectroscopic properties of thulium doped tellurite and thulium doped germanate glass are characterized. Absorption and emission spectra, lifetime, Fourier Transform Infrared Spectroscopy (FTIR), and thermo-gravimetric analysis are utilized to characterize the thulium doped tellurite bulk glass samples. Judd-Oflet theory, Fuchtbauer-ladenburg theory, Kushida's model, Burshtein's hopping model, Miyakawa's non-resonant energy transfer model are employed in ab-initio calculation of cross relaxation energy transfer. The fundamental mechanism of cross relaxation energy transfer is examined through ab-initio calculation and self-calibrating spectroscopy.Thulium doped tellurite glass microspheres are fabricated by spin casting technique. Single mode 2-mm laser is demonstrated from tellurite microsphere with high thulium doping concentration. General laser condition for self-terminating transition is discussed and concluded. Demonstration of 1.5-mm laser is achieved from a self-terminating transition of thulium doped in tellurite microsphere through a cooperative lasing technique.Highly efficient 1.9 micron fiber laser is demonstrated in thulium doped germanate fiber laser. The slope efficiency of the fiber laser is 58%, which indicates a quantum efficiency of 1.79. Single frequency laser operation at 1.9 micron has been successfully accomplished. A fiber based Fabry-Perot interferometer is utilized as a scanning filter to examine the single frequency operation. 4 W laser output has been achieved from a 40 cm long Tm-doped germanate double cladding fiber laser.