| Narrow linewidth fiber lasers have wide applications in laser spectroscopy, optical fiber sensing, lider ranging and coherent optical communications and many other fields. This paper is meant to figure out how to obtain a stable narrow linewidth fiber laser. By selecting the resonant cavity shape, designing the filter and frequency stabilization control method, a series of detailed theoretical analysis and experimental research have been done. The main work is as follows:1. Proposed a narrow linewidth fiber laser of high frequency stabilization implementations. A theoretical model based on the linewidth fiber laser theory has been made to study typically on the shaped resonant cavity factors, the gain medium, the temperature and also the vibration. By using thermostatic control, shock measures, an annular cavity saturable absorber and also some other linewidth compression techniques, the output of narrow linewidth fiber laser of high frequency stabilization has finally be made.2. Set the appropriate concentration and cavity length of the gain medium. Based on the rate equations and power propagation equations, the theoretical models of output power of the ring cavity Er3+ doped fiber laser, threshold power and slope efficiency characteristics have been established. And with expanding the corresponding simulation analysis, the gain medium has been established with a high Er3+ doped fiber of a of 3-meter length.3. Conducted the research of the saturable absorber narrow of the Er3+ doped linewidth fiber laser. The factors of affecting its output spectral linewidth and linear sweep were studied in detail. Experimental device used an annular chamber. An isolation filte was also used to increase the density of cavity longitudinal mode. A 30-meter saturable absorber was used to eliminate the multi-longitudinal mode and suppress the mode hopping. And the corresponding outputs of the narrow linewidth fiber laser were presented. The fiber laser has been exhibited that an operating wavelength is 1550 nm, the output power is 24.3mW, the optical conversion efficiency is given as 12.66%, the slope efficiency comes out as 15.76%, and the wavelength scanning range is 20 nm.. The spectral linewidth is about 4.7kHz by using the delay self-heterodyne measured method.4. Established a laser frequency stabilization system. Based on the output of the laser frequency drift and other factors, a method of frequency discriminator was presented. A monolithic integrated circuit AD8302 was obtained in the frequency discriminator. The system can discriminate the different signal in less than about 10 Hz. Based on that system, the control structures were designed. And with experimental analysis, the PZT drive circuit magnification was given as 66.67. Also the phase shift coefficient at different frequencies of PZT control element was presented. The linear relationship between the MZ interferometer fringe and the applied voltage of PZT was conjectured and verified. As well as the relevant contact between the frequencies drift direction of the laser and that voltage was also presented.5. Established a narrow linewidth fiber laser system of high frequency stabilization. Through the experimental measurements of the system, the amount of frequency drift of the laser is reduce from 860 MHz to 180 MHz. And the width after the addition of a feedback control element has not changed with 5.0kHz. Therefore, the method proposed in this paper is verified by theoretical analysis and experimental results. |
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