Developments of Narrow-Linewidth Q-switched Fiber Laser, 1480 nm Raman Fiber Laser, and Free Space Fiber Amplifiers
KeywordsFree-space fiber amplifier
Q-switched fiber laser
Raman fiber laser
Er/Yb co-doped fiber
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PublisherThe University of Arizona.
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AbstractIn the first chapter, a Q-switched fiber laser that is capable of generating transform-limited pulses based on single-frequency fiber laser seeded ring cavity is demonstrated. The output pulse width can be tuned from hundreds of nanoseconds to several microseconds. This Q-switched ring cavity fiber laser can operate over the whole C-band. In addition, a theoretical model is developed to numerically study the pulse characteristics, and the numerical results are in good agreements with the experimental results. In the next chapter, a Raman fiber laser is developed for generating signal at 1480 nm. Initial experimental results has demonstrated generating of Raman laser at 1175 nm, 1240 nm, 1315 nm, and 1395 nm wavelength. Finally, a free space fiber amplifier is studied both theoretically and experimentally. The experimental work has demonstrated signal coupling efficiency up to 90% in the NP highly Er/Yb co-doped phosphate fiber.
Degree ProgramGraduate College
Degree GrantorUniversity of Arizona
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Optical Fiber Devices: Novel Fiber Lasers and Image AmplifierPeyghambarian, Nasser; Suzuki, Shigeru; Peyghambarian, Nasser; Peyghambarian, Nasser; Schülzgen, Axel; Kueppers, Franko (The University of Arizona., 2008)Three fiber based optical devices: all phosphate glass fiber laser, single hybrid mode fiber laser, and fiber image amplifier, were investigated in this dissertation. Phosphate fiber Bragg grating (FBG) is desired to improve performance of recently developed high power single frequency lasers that were based on highly rare earth ion doped phosphate fibers because these lasers were fabricated with silica FBGs that have incompatible properties with standard phosphate glasses. Since standard phosphate glasses are not photosensitive, Ge-doped phosphate glasses were fabricated and their UV-photosensitivity was examined. A phosphate fiber that has Ge-doped core showed UV index changes more than ~1.1 × 10⁻³. An all-phosphate fiber laser was also demonstrated with the Ge-doped phosphate FBG. Single hybrid mode fiber laser that involves a large area mode in cavity formation was demonstrated. The fiber laser consists of an Er-doped active fiber and two FBGs. One FBG was a core-cladding mode converter, and the other FBG was a narrowband high reflector that selects the lasing wavelength and mode. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area stepindex fibers, and is supposed to suitable for a high power fiber laser. Also this configuration allows us to make novel ring-like cavities and sensor devices that consist of higher mode of optical fibers. Image amplifier based on a highly rare earth ion doped phosphate fiber is a unique approach to overcome weakness of widely used image intensifiers that lose a lot of information in the image, such as spectral distribution, polarization, and phase. Image amplification with a 19-pixel optical image amplifier array based on high gain per unit length Yb³⁺-doped phosphate glass optical fiber was demonstrated. A 10-cm of the 19- pixel fiber image amplifier provides spatially uniform image amplification with gain of 30 dB/pixel or more. This image amplifier responds quickly to changes in the image position – with potential for GHz-level or higher frame rates. This unique approach for image amplification offers low noise, high gain, and wide field of view in a compact fiber-based device.
Multimode Interference in Optical Fibers and Its Applications in Fiber Lasers and AmplifiersPeyghambarian, Nasser; Zhu, Xiushan; Peyghambarian, Nasser; Schulzgen, Axel; Kueppers, Franko (The University of Arizona., 2008)Multimode interference (MMI) in optical fibers has been studied and its applications in optical fiber lasers and amplifiers have been proposed and demonstrated in this thesis. When a single-mode fiber is spliced onto a multimode fiber, quasi-reproduction of the field from the single-mode fiber, also called “self-imaging”, occurs periodically along the multimode fiber where the phase differences between the strongly excited modes are very small. The properties of self-imaging in multimode optical fibers have been investigated experimentally and theoretically in this thesis. Key parameters for the design of MMI-based fiber devices have been defined and their corresponding values have been provides for the 50 μm and 105 μm multimode fibers. By use of the self-imaging effect, a fiber laser with single-transverse-mode output while using a multimode rare-earth-doped fiber has been demonstrated as an alternative route to overcome the constraints of an active single-mode fiber. The first MMI-based fiber laser in the world has provided a perfect beam quality (M² = 1.01) and an inherent narrow spectrum (Δλ(3dB) < 0.5 nm). Linearly-polarized narrow-linewidth single-transverse-mode emission has also been obtained from a MMI fiber laser utilizing a single-mode fiber inscribed with a polarization-maintaining fiber Bragg grating. Moreover, high power MMI fiber lasers and amplifiers utilizing rare-earth doped silica large-core multimode fibers have been proposed and their critical features, such as efficiency, optical spectrum, and beam quality, have been investigated. On the other hand, because exclusively excited LP₀, n modes inside the multimode fiber segment are represented by apertured Bessel fields that have long propagation invariant distances, nondiffracting beams can be generated from the MMI-based fiber devices. In this thesis, the principle of generating nondiffracting beams from multimode optical fibers has been described and the propagation characteristics of the generated beams have been investigated. Active MMI fiber devices to generate tens of watts or even hundreds of watts nondiffracting beams have also been proposed.
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