节点文献
被动锁模波长可调谐光纤激光器的理论和实验研究
Theoretical and Experimental Research on Wavelength-tunable Passively Mode-locked Fiber Lasers
【作者】 白扬博；
【导师】 张贵忠；
【作者基本信息】 天津大学 ， 光电子技术， 2012， 博士
【摘要】 波长可调谐的被动锁模光纤激光器能够广泛地应用于光通信领域，因此本论文主要围绕此课题在理论和实验上展开研究工作。在实验上，利用半导体可饱和吸收镜（SESAM）实现线型腔掺镱光纤激光器的双波长锁模输出；利用非线性偏振旋转（NPR）实现环形腔双包层铒镱共掺光纤激光器的锁模。主要研究工作如下：1.波长可调谐SESAM锁模线型腔掺镱光纤激光器。输出被动锁模脉冲的重复频率为16.42MHz，在中心波长1030nm处，最大平均输出功率为10.2mW，单脉冲能量为0.63nJ。体布拉格光栅（VBG）既作为腔镜，又作为波长调谐器件。转动VBG，锁模脉冲中心波长可在1011.9~1050.6nm（38.7nm）范围内定性定量地调谐。以光栅公式为基础，可以在振荡波长和VBG的倾斜角度之间进行相互推算，建立一一对应关系；当顺时针调节VBG，波长向长波长方向调谐；反之，向短波长方向调谐。2.双波长可分别调谐的SESAM锁模线型腔掺镱光纤激光器。利用保偏分束器构建两个分支激光腔，这两个光腔共享同一段掺镱增益光纤，每个光腔内各对应一块VBG，其不仅作为该分支腔的腔镜，而且作为波长调谐器件。该激光器利用净增益均衡法输出双波长脉冲，其中心波长可分别在1020.3~1038.5nm和1027.2~1055.1nm的范围内定性定量地调谐，其重复频率分别为11.39和11.41MHz，最大单脉冲能量分别为0.47和0.33nJ。双波长脉冲的最大和最小波长间隔为34.8和2.4nm。3. NPR锁模环形腔铒镱共掺双包层光纤激光器。输出被动锁模脉冲的基频重复频率为12.12MHz，中心波长为1568.98nm时，光谱带宽为5.26nm，信噪比约60dB。调节两个偏振控制器，实现锁模脉冲的中心波长在1564.60nm~1568.98nm范围内连续调谐，调谐范围4.38nm。测得的脉宽中，最窄脉宽为1.78ps。当泵浦功率为3.9W时，平均输出功率达到最大值52.2mW。4.自调Q和自锁模环形腔铒镱共掺双包层光纤激光器。逐渐增大泵浦功率，自调Q脉冲的频率从4.17~55.56KHz调谐；同时，脉冲宽度从11.9~8.1μs调谐。自锁模的基频为12.58MHz，在1565.80nm处，光谱带宽为3.15nm；泵浦功率升高至2700mW时，自锁模消失。
【Abstract】 The passively mode-locked fiber laser with central wavelength tunable can bewidely used in optical communication system. Hence, the passively mode-lockedfiber laser which pulse central wavelength can be tuned continuously is mainlystudied theoretically and experimentally in this thesis. In experiment, thedual-wavelength mode-locked pulses are obtained by semiconductor saturableabsorber mirror（SESAM） in linear cavity ytterbium-doped fiber laser. The passivelymode-locked pulse is realized by nonlinear polarization rotation（NPR） in ring cavitydouble-clad erbium/ytterbium co-doped fiber laser. The detail research work can beclassified as follows:1. Wavelength-tunable SESAM mode-locked linear cavity ytterbium-dopedfiber laser. The passively mode-locked pulse with the repetition rate of16.42MHz is achieved, which maximum average output power is10.2mW andsingle pulse energy is0.63nJ at central wavelength of1030nm. Volume Bragggrating（VBG） acts not only as the mirror of the laser cavity, but also thewavelength tuning device. By adjusting VBG, the central wavelength of themode-locked pulse is tuned from1011.9nm to1050.6nm qualitatively andquantitatively, which tuning range of38.7nm. Based on the grating formula,every output wavelength matches one of the angles of VBG. Through adjustingthe VBG along clockwise, the pulse wavelength is tuned to longer wavelength;conversely, it becomes shorter.2. Wavelength tunable dual-wavelength linear-cavity passively mode-lockedYtterbium-doped fiber laser based on SESAM. This fiber laser is constructedwith an Yb-doped fiber and two branch cavities by polarization-maintaining beamsplitter. This laser system can output simultaneous dual-wavelength pulses withthe qualitative and quantitative wavelength tuning range of1020.3~1038.5nm and1027.2~1055.1nm by net gain equalization method at room temperature with themaximum and minimum wavelength separation of34.8and2.4nm, whichrepetition rate of11.39and11.41MHz respectively. And their maximum singlepulse energy are0.47and0.33nJ.3. The mode-locked ring cavity double-clad erbium/ytterbium co-doped fiberlaser based on nonlinear polarization rotation. The passively mode-locked pulse is obtained with the repetition rate of12.12MHz, which optical spectrum bandwidthis5.26nm and signal-to-noise ratio is60dB at the central wavelength of1568.98nm. The minimum pulse duration is1.78ps. The central wavelength ofthe mode-locked pulse is tuned from1564.60nm to1568.98nm by adjustingpolarization controller with the tuning range of4.38nm. The maximum averageoutput power is52.2mW at the pump power of3.9W.4. Self-Q-switched and self-mode-locked ring cavity double-claderbium/ytterbium co-doped fiber laser. When increasing the pump powergradually, the repetition rate of the Self-Q-switched pulse is tuned from4.17KHzto55.56KHz. At the same time, the pulse duration is tuned from11.9μs to8.1μs.The repetition rate of the self-mode-locked pulse is12.58MHz with the opticalspectrum bandwidth of3.15nm at1565.80nm. The self-mode-locked pulsedisappears when the pump power is higher than2700mW.