基于环形滤波镜的单频掺镱光纤激光器研究

发布时间：2018-10-20 10:43

【摘要】：单频光纤激光器是指在光学的谐振腔内只有一个纵模输出的光纤激光器,因而又称为单纵模光纤激光器,因其转换效率高、相干性好、结构简单紧凑及线宽窄等特点而广泛应用于光通信、光纤传感、精密测量等领域。本文采用光纤环形镜与可饱和吸收体相结合将其应用到线性腔的方法来实现1064 nm的单频光纤激光输出,而后将实验所得到的单频激光作为种子光进行了功率放大,主要工作及研究内容为：1.理论分析了掺镱光纤的能级结构、光谱特性,并对最佳的光纤长度及线性腔内功率的分布进行了计算。基于光纤环形镜的工作原理,将其与可饱和吸收体结合形成光纤环形滤波镜,理论分析了环形滤波镜的滤波原理及工作机制,包括动态光栅的形成机理。分析了石墨烯之所以在光纤环形镜及单频光纤激光器中作为可饱和吸收体的原因。2.实验中采用可饱和吸收体应用到光纤环形镜并将其置于线性腔中的方法来实现单频光纤激光器。分别使用掺镱光纤和石墨烯作为环形滤波镜中的可饱和吸收体,通过不断调节两个偏振控制器,实现了中心波长1064 nm的稳定单频激光输出,功率稳定性达到98%以上,信噪比为60 dB,其中使用掺镱光纤作为可饱和吸收体获得阈值30 mW、最大输出功率为32 mW、斜率效率为33.8%的单频激光输出,而使用石墨烯作为可饱和吸收体则得到了阈值26 mW、最高输出功率为16 mW,斜坡效率为15%的单频激光输出。使用光纤延时自外差的方法测得其输出线宽为5 kHz。3.在实现了稳定的单频激光输出后,将其输出的信号作为种子光进行了功率放大。实验采用MOPA放大系统,先后分别使用2m、5m、10m的掺镱光纤作为增益介质,经实验比较,发现长度为5m时所获得的输出功率效果最好,其中在泵浦光最大为300 mW时,得的单频激光放大功率为160 mW,增益系数14.3 dB,放大倍数为26.7倍。
[Abstract]:Single-frequency fiber laser is a kind of fiber laser with only one longitudinal mode output in the resonator of optics, so it is also called single-longitudinal-mode fiber laser, because of its high conversion efficiency and good coherence. It is widely used in optical communication, optical fiber sensing, precision measurement and so on due to its simple and compact structure and narrow line width. In this paper, the single frequency optical fiber laser output of 1064 nm is realized by combining the optical fiber ring mirror with saturable absorber to the linear cavity, and then the experimental single frequency laser is used as the seed light to amplify the power. The main work and research contents are as follows: 1. The energy level structure and spectral characteristics of ytterbium-doped fiber are theoretically analyzed. The optimal fiber length and the distribution of power in the linear cavity are calculated. Based on the working principle of fiber annular mirror, the fiber ring filter mirror is formed by combining it with saturable absorber. The filtering principle and working mechanism of ring filter mirror are analyzed theoretically, including the formation mechanism of dynamic grating. The reason why graphene is a saturable absorber in fiber ring mirror and single frequency fiber laser is analyzed. In the experiment, a single frequency fiber laser is realized by applying saturable absorber to the optical fiber ring mirror and placing it in a linear cavity. Ytterbium-doped fiber and graphene are used as saturable absorbers in annular filter mirror respectively. By adjusting two polarization controllers continuously, the stable single-frequency laser output with a central wavelength of 1064 nm is achieved, and the power stability is over 98%. The signal-to-noise ratio (SNR) is 60 dB, in which ytterbium-doped fiber is used as the saturable absorber to obtain the single-frequency laser output with a threshold of 30 mW, with a maximum output power of 32 mW, slope efficiency of 33.8%. Using graphene as a saturable absorber, a single frequency laser output with a threshold of 26 mW, with a maximum output power of 16 mW, slope efficiency of 15% was obtained. The output linewidth of the fiber delay self-heterodyne is measured to be 5 kHz.3.. After the stable single frequency laser output is realized, the output signal is amplified as seed light. The MOPA amplification system is used in the experiment, and the ytterbium-doped fiber with 2mt 5mt 10m is used as the gain medium respectively. Compared with the experiment, it is found that the output power is the best when the length is 5 m, especially when the pump light is up to 300 mW. The gain factor of the single frequency laser is 14.3 dB, and the gain factor of 160mW, is 26.7 times.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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