| Summary: | 碩士 === 國立嘉義大學 === 電子物理學系光電暨固態電子研究所 === 101 === In this study, we made use of an erbium-doped fiber amplifier and single-mode fibers in series to construct a ring resonator for producing a wavelength tunable fiber laser. First, when using flat-end optical fibers to form a butt joint, displacing the receiving-end fiber’s location could lead to dual wavelength switching. To investigate the reason for the laser wavelength conversion, we tried to adjust the output intensity of the erbium-doped fiber amplifier, but the laser wavelength did not change, excluding the cause related to the erbium-doped fiber amplifier’s gain. Then, we rebuilt a fiber ring laser system by the erbium-doped fiber amplifier. We set up a free space section in the middle, and added a circular continuously adjustable neutral density attenuator to modulate the loss inside the laser resonator. The resultant fiber laser output wavelength could be switched from 1559 nm to 1532 nm approximately, similar to the previously observed experimental result by displacing the flat-end optical fiber butt joint. We also derived a light beam by using a beam splitter in the free space section, and used a camera to observe the fiber cross-sectional modal distribution. We have made sure that in the fiber laser output light there is only a single fundamental mode in the fiber core, and no higher-order cladding modes exist in the fiber. Such a fiber laser wavelength conversion is related to the dynamic change of nonlinear optical gain characteristics of the laser gain medium (erbium-doped fiber). Finally, we also utilized the method of heating and stretching and the method of UV photolithography to fabricate a variety of fiber tips, hoping that we can produce continuously wavelength tunable fiber lasers by this type of specialty optical fibers or waveguide devices.
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