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Spectral Beam Combining Of High Power Narrow Linewidth Ytterbium-doped Allfiber Superfluorescent Sources

Posted on:2017-02-27Degree:MasterType:Thesis
Country:ChinaCandidate:S Y WeiFull Text:PDF
GTID:2348330503492993Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
As a specific type of solid-state laser, fiber lasers get many advantages such as compact structure, high energy conversion efficiency, good beam quality and antienvironmental disturbance ability. Currently, fiber laser has been widely applied in laser processing and manufacturing, communication and remote sensing, medical treatment, military defense security and other fields. As the large mode area double cladding fiber arises, the manufacture process of optics components and high power diode laser pump sources become mature, tens of kilowatts continuous wave laser output has achieved in a single fiber by using large mode area double cladding fibers to reduce nonlinear effects under condition of high power operation. But the beam quality is not ideal, and output power is difficult to increase significantly due to fusing point damage and thermal damage inside the fiber. In order to acquire high power output with good beam quality, break the bottleneck of the highest output power from a single fiber, spectral beam combing by using high power narrow linewidth fiber laser has been proposed. But narrow linewidth continuous wave fiber lasers under high power operation will trigger stimulated Brillouin scattering effect easily. Superfluorescent sources as a new pattern of high-brightness fiber light source, have both laser and fluorescent characteristics. In addition with no self-pulse, no relaxed oscillation, no modecompetition and high time stability at the same time. Superfluorescent sources are easily to get a stable high power output through fiber amplifiers with high stimulated Brillouin scattering threshold. These advantages mentioned above make high power narrow linewidth superfluorescent sources have more potential to apply in spectral beam combining. In this thesis, we carry out a systematic study on narrow linewidth fiber superfluorescent source and spectral beam combining, and demonstrate experimentally the feasibility of beam combining by using narrow linewidth fiber superfluorescent sources, main contents conclude as follows:(1) The ytterbium-doped all-fiber narrow bandwidth superfluorescent sources were demonstrated experimentally and theoretically. The stable narrow bandwidth superfluorescent seed sources with central wavelength of 1060 nm and 1078 nm, which 3 d B spectral bandwidth are both 0.05 nm, was achieved by using circulators and FBGs as filters in the setup.(2) Two narrow bandwidth superfluorescent seed sources was amplified by utilizing main oscillator power amplification structure. High power fiber amplifier systems were used to boost the output power up to 57.4 W and 56.6 W respectively with the slope efficiency of 66.6% and 66.7% by using 20/130 ytterbium-doped double cladding fibers. The bandwidth of the superfluorescent sources at 1060 nm and 1078 nm were both 0.05 nm. Two channels narrow bandwidth superfluorescent sources beam combining by using transmission grating were researched theoretically and demonstrated experimentally. Combining output power of 104.2 W with the combining efficiency of 91.3% were achieved in case of output power reaching maximum in both channels.(3) To get higher superfluorescent sources output power, the new main amplifiers have been constructed by changing main amplifiers structure and replacing doped fibers with 20/400 ytterbium-doped double cladding fibers. Output power of 225.8 W were obtained in both narrow bandwidth superfluorescent sources, 3 d B spectral bandwidth was broadened slightly while amplifying the seed sources to maximum output power, 1060 nm and 1078 nm superfluorescent sources were broaden from 0.042 nm and 0.052 nm to 0.07 nm and 0.063 nm respectively. Combining output power of 406 W with the combining efficiency of 87% were achieved in case of maximum output power of both channels. In the two structures mentioned above, shifting of center wavelength and beam quality deterioration haven't been found during the amplification and spectral beam combining processes.
Keywords/Search Tags:Fiber superfluorescent source, fiber amplifier, ytterbium-doped fiber, beam combining
PDF Full Text Request
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