1.6 微米E r : YAG 透明陶瓷激光技术
文献类型：学位论文
| 作者 | 张笑琪 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 范滇元 |
| 关键词 | Er:YAG 透明陶瓷 石墨烯 调 Q 激光 1.6 微米 人眼安全 |
| 其他题名 | 1.6 μm Er:YAG Polycrystalline Ceramic Laser Technology |
| 中文摘要 | 透明陶瓷激光材料是近年来新发展起来的继玻璃和单晶后的第三类激光材料，热导率高、耐热冲击强度大、可大尺寸制备、掺杂浓度灵活可控等，结合了玻璃和晶体的共同优点，发展潜力甚大。 对陶瓷材料的激光运转性能的研究和考核，关系到新材料能否得到实际的应用，已是当前普遍关注的研究课题。近年来，工作在1微米波段的掺杂Nd3+和Yb3+陶瓷介质激光器已有了较多的研究并取得积极成效，对其他波段、其他掺杂离子的陶瓷激光器也已提到研究日程上。鉴于1.6微米波段激光具有人眼安全特性，位于大气窗口，在激光雷达、遥感探测、空间通讯及光谱学等众多领域有广泛的应用需求，本论文选用掺杂Er3+离子的YAG透明陶瓷为样本，研究其在1.6微米波段的激光运转性能。 本论文在理论和实验上深入细致地研究了连续振荡体制下Er:YAG透明陶瓷的激光调谐和谱线窄化特性；以及在重频脉冲工作体制下的调Q激光运转性能。 采用1532 nm激光共振泵浦、体布拉格光栅调谐等技术，首次在Er:YAG激光器中实现了三个子区间共23.1 nm的调谐宽度，并且首次获得了1634 nm发射峰的激光振荡。首次研究了宽带饱和吸收体石墨烯，在1617 nm的调Q性能，实现了1.9微秒的稳定调Q脉冲运转。使用高饱和通量密度的Cr:ZnSe作饱和吸收体，获得了最短28.2 ns的调Q脉冲输出，相应的峰值功率为11.3 kW，脉冲重复频率为2.16 kHz。所得脉冲调Q运转性能和已报道的Er:YAG单晶处于同一水平。相关创新性研究论文发表于Optics Express、IEEE PTL等刊物和学术会议报告。 本论文研究内容主要包括： 一、利用体布拉格光栅作为调谐元件，首次对Er:YAG透明陶瓷在1.6微米的调谐性能进行了系统的研究。调谐范围分为3个区间：1614.2 nm-1621.5 nm，1629.3 nm - 1635.1 nm和1639.2 nm-1649.2 nm，实现了总共23.1 nm的调谐宽度，每个区间功率输出曲线都跟此区间发射峰对称。从理论上说明了在没有任何选频元件的情况下，1634 nm发射峰的激光由于其他两个波长的竞争，是不可能振荡产生的。本文利用VBG作为选频元件首次实现1634 nm发射峰附近的激光振荡输出。在最大泵浦功率11.1 W时，利用透过率为10%的输出镜，在1633.0 nm获得最大1.4 W输出功率，相对于入射光泵浦功率斜效率为20.9%。在整个调谐范围内，调谐激光器的光谱宽度（FWHM）不超过0.05 nm，证明了VBG的光谱窄化作用。相关工作发表在Optics Express上。 二、首次研究了石墨烯在1617 nm的调Q性能。利用脉宽为350 ns，重复频率为2 kHz的1645 nm单晶Er:YAG声光调Q激光器，对所用石墨烯样品的饱和通量和调制深度进行了测量，测得饱和通量密度为10.2 mJ/cm2，调制深度为19.9%。利用掺杂浓度为0.5 at.%的Er:YAG透明陶瓷增益介质，实现了最短脉宽为1.9 μs，重复频率54.4 kHz，单脉冲能量为12.2 μJ的1617 nm稳定调Q运转，结果与目前报道的单晶处于相同水平。相关工作已发表在IEEE PTL上。 三、利用Cr:ZnSe作为饱和吸收体，对Er:YAG透明陶瓷的调Q性能进行了实验研究，实现了最短脉宽为几十个纳秒的调Q脉冲输出。 (1) 从调Q速率方程出发，考虑激光和泵浦光为高斯分布，忽略能量上转换的影响，研究了泵浦光面积、被动饱和吸收体上的光斑面积、腔长、饱和吸收体初始透过率、输出镜透过率对调Q激光器单脉冲能量、脉宽及峰值功率的影响。发现当参数α较小时，输出镜透过率对脉宽的影响较小，饱和吸收体的初始透过率对脉宽的影响比较大，实验结果和这一理论模拟一致。 (2) 使用不同透过率的输出镜，不同初始透过率的Cr:ZnSe饱和吸收体，对掺杂浓度为1 at.%（长度为14 mm）和0.5 at.%（长度34 mm）的Er:YAG透明陶瓷样品的进行了调Q实验研究。研究了脉冲宽度和脉冲重复频率跟入射泵浦功率的关系。最终利用掺杂浓度0.5 at.%的Er:YAG透明陶瓷实现了最短脉宽28.2 ns的1617 nm稳定调Q脉冲输出，相应的脉冲峰值功率为11.3 kW，脉冲重复频率为2.17 kHz。理论分析给出获得ns量级的调Q脉冲的技术途径。相关工作已投稿Optics Material Express。 |
| 英文摘要 | Recently, polycrystalline ceramics laser materials have emerged as a novel laser medium compared with conventional single crystals and glass. Transparent ceramics have the advantages of both single crystals and glass, such as rapid and large volume fabrication, flexibility in doping concentration and profile, high thermal conductivity and high resistance to laser damage. Thus the laser ceramics could be a promising candidate for high-power laser generation. At present, it has become a very popular subject to research and test the laser performance of the ceramic materials, which decides the practical applications of the novel laser medium. Recent years, 1 μm Nd3+ and Yb3+ activated ceramics lasers have been widely studied and gotten tremendous achievements. Transparent ceramics doped with other rare earth ions operating at other wavelength have also been put forward to study. Driven by nose cones of the applications of the 1.6 μm eye-safe laser in lidar, remote sensing and ranging, free-space communications and spectroscopy etc., in this dissertation, we adopted Er:YAG transparent ceramics as the laser medium and study their laser performance at 1.6 μm. In this dissertation, we theoretically and experimentally studied the tunable performance of the Er:YAG ceramic lasers in continuous-wave mode and the laser performance of the Er:YAG ceramic laser in Q-switched mode. By using the 1532 nm resonantly pumping technology and the volume Bragg grating, the tunable properties of the Er:YAG ceramic laser was studied for the first time. A total tuning range of 23.1 nm composed of three parts was obtained. The laser operating at around 1634 nm was demonstrated for the first time. Stable Q-switched laser with pulse duration of 1.9 μs operating at 1617 nm were demonstrated by adopting graphene (characterized by ultra-broad absorption band) as a saturable absorber. By using the Cr:ZnSe (characterized by high saturation energy density) as a saturable absorber, the Er:YAG ceramic laser yielded pulses of 28.2 ns duration at a pulse repetition rate of 2.17 kHz. The corresponding peak power was up to 11.3 kW. The performance of the Er:YAG ceramic laser operating in Q-switched mode is a little better than that of the single crystals reported until now. The relevant innovative results have been published in Optics Express, IEEE PTL and other journals. The main results are summarized as follows. 1. By using a volume Bragg grating, we have researched the tunable performance of the Er:YAG ceramic laser for the first time. The total tuning range of 23.1 nm was composed of three parts, i.e. 1614.2 nm -1621.5 nm, 1629.3 nm - 1635.1 nm and 1639.2 nm -1649.2 nm. In every tuning range, the output power as a function of the wavelength was symmetric with respect to its emission peak. In theory, the 1634 nm transition cannot be obtained without a wavelength selector, due to the weaker oscillating strength compared with those of the 1617 nm and 1645 nm transitions. In this dissertation, we demonstrated the laser oscillation at around 1630 nm for the first time by using volume Bragg grating. In the tuning range of 1629.3 nm - 1635.1 nm, we obtained a maximum output power of 1.4 W at 1633.0 nm at the maximum incident pump power of 11.1 W, corresponding to a slope efficiency of 20.9% with respect to the incident pump power. The bandwidth of the output spectrum of the tunable Er:YAG ceramic laser did not exceed 0.05 nm (FWHM) over the whole tuning range, which demonstrates the spectral discrimination property of the volume Bragg grating. The paper about this research has been published in Optics Express. 2. We reported the performance of the graphene used as a saturable absorber in the 1617 nm Er:YAG ceramic laser for the first time. Using an acousto-optic Q-switched Er:YAG laser with pulse duration of 350 ns at a repetition rate of 2 kHz as the probe laser, the saturation energy density and modulation depth of the graphene were measured to be 10.23 mJ/cm2 and 19.9% respectively. In the experiment, we adopted an Er:YAG polycrystalline ceramic with 0.5 at.% Er3+-doping as the gain medium. Stable Q-switched laser pulses with pulse duration of 1.9 μs and pulse energy of 12.2 μJ were yielded at a pulse repetition rate of 54.4 kHz. The laser performance of the graphene Q-switched Er:YAG ceramic laser is a little better than that of the single crystals reported until now. The paper about this research has been published in IEEE PTL. 3. We reported on a passively Q-switched polycrystalline ceramic Er:YAG laser by using a Cr:ZnSe as a saturable absorber. Pulse duration of the order of tens ns was realized. (1) We analyzed the passively Q-switched Er:YAG ceramic laser by using rate equation. For a more accurate theoretical analysis, the intracavity photon density and the initial population-inversion density of the gain medium and the saturable absorber are assumed to be Gaussian spatial distributions. The energy-transfer-upconversion of the gain medium was negligible. We study the pulse duration, pulse energy and peak power as a function of parameters, such as the beam cross-section areas in the gain medium and in the saturable absorber, the length of the laser cavity, the initial transmission of the saturable absorber and the reflectivity of the output coupler. The theoretical analysis shows that the pulse duration of the passively Q-switched Er:YAG ceramic laser is mainly determined by the initial transmission of the saturable absorber and slightly affected by the transmission of the output coupler. The results of the numerical simulation are in good agreement with those obtained in the experiment. (2) With output couplers of different reflectivity and saturable absorbers of different initial transmission, we experimentally studied the Q-switched performance of the Er:YAG ceramic laser by adopting two ceramic samples with doping levels of 1 at.% and 0.5 at.%. The pulse duration and repetition rate as a function of the pump power were given. We obtained the minimum pulse duration of 28.2 ns at pulse repetition rate of 2.17 kHz by using the ceramic sample with doping levels of 0.5 at.%. The corresponding peak power was up to 11.3 kW. The prospects for further narrowing down the pulse were given. The paper about this research has been submitted to Optics Material Express. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15895]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张笑琪. 1.6 微米E r : YAG 透明陶瓷激光技术[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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