| Summary: | 博士 === 國立交通大學 === 光電工程研究所 === 105 === In this dissertation we have experimentally and theoretically investigated 3 kinds of intra-cavity comb filter assisted high repetition rate mode-locked lasers. The inserted comb filters include the birefringence filter, the low-Q Fabry-Pérot etalon, and the high-Q Fabry-Pérot etalon. By utilizing the highly nonlinear fiber and comb filter, stable mode-locking with the repetition rate up to 100 GHz can be achieved along with the induced four wave mixing effect and the nonlinear polarization rotation effect.
In the birefringence filter assisted hybrid mode-locked Er-doped fiber laser, 100 GHz - 400 GHz burst-mode hybrid mode-locking has been successfully demonstrated by using 10 GHz - 25 GHz phase modulation and a section of 7.7 m polarization-maintaining fiber that acts as a 100 GHz birefringence filter. A new effect analogous to rational harmonic mode-locking has also been discovered, with which the operation state of the laser can be switched between the 100 GHz and 300 GHz burst-mode mode-locking states by merely detuning the modulation frequency around 200 kHz. In simulation, the distributed master equation model is used to investigate the operation of the laser under the hybrid mode-locking state and the repetition rate multiplied mode-locking state.
In the low-Q Fabry-Pérot etalon assisted hybrid mode-locked Er-doped fiber laser, 100 GHz passive mode-locking and 100 GHz burst-mode hybrid mode-locking have been generated by inserting an etalon with the finesse of 6. The dependence of the burst envelope width and the phase modulation depth is found to follow the relationship of inverse square root. The distributed master equation model is used to reveal the underlying physical mechanisms and confirm the observed experimental results. The tendency of most laser characteristics are consistent with the experimental results. In particular, the requirement of modulation frequency detuning for achieving stable burst-mode hybrid mode-locking is clarified.
In the high-Q Fabry-Pérot etalon assisted hybrid mode-locked Er-doped fiber laser, 100 GHz pulse trains are generated under pure passive mode-locking and hybrid mode-locking by using a high-Q etalon with the finesse of 100. It is found that the phase modulation can enhance the auto-correlation contrast of the pulse train by 3.4 dB compared with the pure passive mode-locking case. Better mode-locked pulse trains at high repetition rates can be generated.
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