基于非线性放大环形镜的全光纤掺铥激光器的实验研究

发布时间：2018-05-27 09:02

本文选题：掺铥光纤激光器 + 非线性放大环形镜　；参考：《深圳大学》2015年硕士论文

【摘要】：掺铥光纤具有极其丰富的荧光光谱,采用不同的泵浦技术,可以获得1650 nm至2150 nm的长波长激光输出。而中心波长位于2μm附近的激光正处于水分子的红外吸收峰,在外科手术或眼部的治疗上都有着卓越的表现。同时,2μm激光在非线性频率转换、超低损耗长距离通信、工业制造等应用领域都有着巨大的潜力。本文对基于非线性放大环形镜(nonlinear amplified loop mirror,NALM)的全光纤被动锁模掺铥激光器进行了实验研究。其中包括对激光器运行在全反常色散环境下的孤子动力模式和运行在净正常色散环境下的耗散孤子共振的研究。具体内容如下:(1)搭建了谐振腔长度为116 m的基于NALM的全光纤被动锁模掺铥激光器,谐振腔在2μm波长范围表现为全反常色散。当泵浦功率超过锁模阈值时,稳定的锁模状态被轻易触发,重复频率为1.72 MHz。在基频锁模下,激光器输出的孤子锁模脉冲中心波长位于1965.67 nm,并存在凯利边带。适当调节偏振控制器,凯利边带消失,光谱变得平滑,半高全宽增加,此时激光器输出类噪声锁模脉冲。增大泵浦功率,进一步调节偏振控制器,锁模脉冲变得不稳定并开始分裂,最终形成了孤子雨。在触发孤子雨状态之后,继续调节腔内偏振态,一种反孤子雨现象——孤子释放被观察到。进一步调节腔内偏振态,流动光孤子的数量逐渐减少并最终消失,此时激光器输出一种高能量的类矩形脉冲。随着泵浦光功率的增加,它的最大脉宽和脉冲能量分别可达33 ns和37.7 n J。在增大泵浦功率的过程中,类矩形脉冲始终保持着单脉冲运转。(2)搭建了谐振腔长度为64.3 m的基于NALM的全光纤被动锁模掺铥激光器,引入了超高数值孔径光纤作为色散补偿元件,谐振腔在2μm波长范围表现为净正常色散,总色散量为+0.8585 ps~2@1900 nm。当泵浦功率超过锁模阈值时,稳定的锁模状态被轻易触发,重复频率为3.11 MHz。在基频锁模下,激光器输出中心波长位于1941.08 nm,脉冲宽度为1.39 ns的矩形脉冲,其平均输出功率为11.8 m W,对应的单脉冲能量为3.79 n J。当谐振腔满足耗散孤子共振条件时,随着泵浦光功率的增加,矩形脉冲持续加宽,其最大脉冲宽度和脉冲能量分别为6.19 ns和19.5 n J,峰值功率被钳制在3.15 W附近。此外,通过适当调节偏振控制器,矩形脉冲的中心波长可以从1940.22 nm被调节到1969.17 nm,存在28.95nm的波长可调谐范围。
[Abstract]:Thulium doped fiber has abundant fluorescence spectra, and the long wavelength laser output from 1650 nm to 2150 nm can be obtained by using different pumping techniques. The laser with a central wavelength of about 2 渭 m is at the infrared absorption peak of water molecules and has excellent performance in surgery or eye treatment. At the same time, 2 渭 m laser has great potential in nonlinear frequency conversion, ultralow loss long distance communication, industrial manufacturing and so on. An all-fiber passively mode-locked thulium doped thulium laser based on nonlinear amplified loop mirror is studied experimentally in this paper. This includes the study of the dynamic mode of the soliton operating in the fully anomalous dispersion environment and the resonance of the dissipative soliton operating in the net normal dispersion environment. The main contents are as follows: 1) an all-fiber passively mode-locked thulium doped laser with a length of 116m is built based on NALM. The resonator exhibits all anomalous dispersion in the wavelength range of 2 渭 m. When the pump power exceeds the mode-locking threshold, the stable mode-locked state is easily triggered, and the repetition rate is 1.72 MHz. The center wavelength of the soliton mode-locked pulse is located at 1965.67 nm and there is a Kelly sideband under the fundamental frequency mode-locking. When the polarization controller is adjusted properly, the Kelly sideband disappears, the spectrum becomes smooth and the full width of the half-height increases, and the laser outputs a noise-like mode-locked pulse. When the pump power is increased and the polarization controller is further adjusted, the mode-locked pulse becomes unstable and begins to split, resulting in the formation of soliton rain. After triggering the state of the soliton rain, the polarization state in the cavity continues to be adjusted, and an anti-soliton rain phenomenon is observed-the release of the soliton is observed. Further adjusting the polarization state in the cavity, the number of mobile solitons gradually decreases and finally disappears. At this time, the laser outputs a kind of high-energy rectangular pulse. With the increase of pump power, the maximum pulse width and pulse energy can reach 33 ns and 37.7 n J, respectively. In the process of increasing pump power, the quasi-rectangular pulse always keeps the single pulse running. (2) an all-fiber passively mode-locked thulium doped laser based on NALM with cavity length of 64.3 m is built, and ultra-high numerical aperture fiber is introduced as dispersion compensation element. The resonator exhibits a net normal dispersion in the wavelength range of 2 渭 m, with a total dispersion of 0.8585 ps~2@1900 nm. When the pump power exceeds the mode-locking threshold, the stable mode-locked state is easily triggered, and the repetition rate is 3.11 MHz. The output center wavelength of the laser is 1941.08 nm and the pulse width is 1.39ns. The average output power is 11.8mW and the corresponding single pulse energy is 3.79nJ. When the cavity satisfies the dissipative soliton resonance condition, the rectangular pulse continues to widen with the increase of pump power. The maximum pulse width and pulse energy are 6.19 ns and 19.5nJ, respectively, and the peak power is clamped at 3.15 W. In addition, by properly adjusting the polarization controller, the center wavelength of the rectangular pulse can be adjusted from 1940.22 nm to 1969.17 nm, and there exists a tunable wavelength range of 28.95nm.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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