LD侧面泵浦Nd:YAG激光器介质板温度特性的研究
文献类型：学位论文
| 作者 | 方爱平 |
| 学位类别 | 硕士 |
| 答辩日期 | 2002 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 楼祺洪 |
| 关键词 | LD泵浦 固体激光介质板 温度分布 光束质量 |
| 其他题名 | Study of the temperature characteristics of LD side-pumped Nd:YAG laser slab |
| 中文摘要 | 该论文主要研究侧向激光二极管列阵泵浦Nd:YAG激光器介质板条的温度特性.研究温度特性与激光光束质量的关系,并通过温度特性的改善,提高侧向LD泵浦固体激光器的光束质量.用激光二极管列阵对固体激光作侧向泵浦时,激光介质板条中的温度不再是简单的呈一维分布,而是作二维考虑.由于激光输出依赖于介质的温度分布及冷却效果,对激光介质温度测量显得十分重要.常规的温度计只能测量平均温度或某一点的温度.为此,该论文提出了一种红外热像仪测量温度的方法,测量介质截面上的温度分布.所测的激光介质板平面x-y的尺寸为5mm×3mm,热像仪在激光输出的轴向上,距离此平面约1m处观测摄像,得到平面热分布相应的热像图.利用相应的软件读取平面内各点的温度值,做出等温图.平面内温度大致呈辐射状分布,在泵浦点处温度最高,距离泵浦点越远温度越低.当x位置固定时,温度在y方向近似为一种抛物线分布,顶点在y=0处.当y位置固定时,温度在x方向的分布则近似为一种双曲线.为了深入分析热导过程,我们运用稳态的有限差分法对实验条件下激光介质平面内的温度分布进行理论计算.将激光介质及其周围的铜块热沉,冷却流体全部作为对象进行分析,选取等间距的节点,写出每个节点所满足的边界条件方程.利用MATLAB编制程序,计算得到所测平面内的温度分布,同样做出等温图.发现实验和理论的结果基本相符,温度的分布规律大致相同. |
| 英文摘要 | In this paper, the temperature characteristics of LD side-pumped Nd:YAG laser slab are investigated through both experiment and theory. The dependence of the laser beam quality on the temperature characteristics is studied. With the improvement of the temperature distribution, the beam divergence angle of the LD side-pumped Nd:YAG laser is reduced. When solid state laser is side-pumped by laser diode array, the temperature distribution of the laser slab is no longer correlated with one axis. Because laser output is dependent on temperature distribution and cooling effect of the laser crystal, it is very important to measure the temperature distribution. The common thermometer can only measure the average temperature or temperature of one point. So a new method is put forward to use an IR camera. The dimension of Nd:YAG crystal is 5mm x 3mm in x-y plane. The IR camera, located at one point along the axial direction, about lm far from the laser slab, takes pictures of the actual infrared thermal distribution under different LD pump power. The temperature distribution value is gotten through special software, and some contour images are drawn. The experimental results show that the temperature in the certain plane has a radiant distribution. The highest value is located at the pump point. The more far from that point, the lower the temperature is. At fixed position in x axis, the temperature distribution along y axis is seemly parabola-like profile with acme at y=0. And when y fixed, the temperature distribution along x axis is hyperbola-like profile. Moreover, theoretical calculation for the temperature distribution in Nd:YAG plane has been carried out by the finite difference method at stable state. The analyzed objects include laser slab, Cu, cooling water and air. In the plane, the chosen points have equal space along x axis and y axis between each other. The heat equations for every point are written. The corresponding Matlab program is edited to calculate the temperature value. The temperature contour is drawn. It is said that the experimental results agree well with the theoretical ones and give the same distribution trend as the latter. The cooling setup is improved based on the experimental and theoretical calculation results as above. The temperature distribution in this situation is given by IR camera measurement and finite difference method calculation respectively. Through the comparison, it concludes that better cooling setup help give better temperature distribution uniformity. The beam distribution of output laser is measured using the method of moving slot, under the two kinds of cooling setup. And the beam quality factor M2 is calculated. With better cooling setup, M2 is reduced from 6.7 to 2.3, which stands for the better mode quality. In this paper, a real-time method for measuring the temperature distribution of laser crystal is suggested. It provides a reliable basis for the design of cooling setup of LD pumped solid state laser. The more uniform temperature distribution is gotten through reasonable cooling setup, the better laser beam quality will be. The effect of the UV excimer laser energy density on the surface morphology of the polyester is also investigated. The laser is SY-200 308nm excimer laser. In order to obtain uniform irradiation, the method of scanning to and fro is given. The irradiation on the polyester induced a characteristic on its surface. The different image under different energy density is given. At 160mj/cm2, the best energy density, the original smooth surface of the polyester changed its morphology to a rather regular roll -like structure perpendicular to the fiber axis after the treatment. The effect of the operated times n on the image under fixed energy density is studied. When n is more than 5, the uniformity is enough for treatment. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16544]  |
| 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 | 方爱平. LD侧面泵浦Nd:YAG激光器介质板温度特性的研究[D]. 中国科学院上海光学精密机械研究所. 2002. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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