| Summary: | 碩士 === 國立交通大學 === 顯示科技研究所 === 103 === In this thesis study we mainly utilize EO phase modulation as the active mode-locking mechanism to build a mode-locked fiber laser. The semiconductor optical amplifier (SOA) is used as the gain medium and a fiber-type Lyot filter is inserted inside the laser cavity for optical filtering. The mode-locked SOA fiber laser can be operated at the single wavelength mode-locking state as well as the dual wavelength mode-locking state. Under single wavelength mode-locking, the laser can generate a 10 GHz pulse train with the average power of 2 mW and pulse width of 18 ps. The pulse width can be reduced below 10 ps by using a section of dispersion compensating fiber for external compression. Under dual wavelength mode-locking, if we let the output pulses propagate through a dispersive fiber, the fiber dispersion can be accurately calculated from the time delay change of the two pulses after a known propagating length. The calculated value is in excellent agreement with the known specification of the fiber.
We have also replaced the phase modulation with the amplitude modulation for comparison. Under different pump currents and modulation intensities, the bandwidth, pulse width, time-bandwidth product and super-mode suppression ratio of the lasers are recorded. The results under the two modulation mechanisms in the same laser structure at the repetition rate of 10 GHz are carefully compared.
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