波长分离膜在多波长激光辐照下的损伤特性研究
文献类型：学位论文
| 作者 | 严磊 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 魏朝阳 |
| 关键词 | 波长分离膜，损伤形貌、阈值，同时辐照，节瘤 |
| 其他题名 | Multi-wavelength lasers-induced damage performance of beam splitters |
| 中文摘要 | 波长分离膜可以使某一波长的激光高反射而其余波长的激光高透射，主要应用于激光分离系统。本文以提高波长分离膜的损伤阈值为目标，实验研究了其在多波长激光同时作用下的损伤规律，初步探索了其损伤机制，具体研究成果如下。 详细分析了倍频分离膜在532 nm和1064 nm激光单独和同时作用下的损伤形貌特征和损伤阈值变化情况。获得的典型损伤形貌显示，不同波长激光的损伤机制完全不同。为了分析1064 nm激光等效为532 nm激光的能量转换系数，详细测定了在不同1064 nm激光能量下，532 nm激光损伤阈值的变化趋势，发现小能量的1064 nm激光会和532 nm激光相互耦合促进损伤发生，而大能量的1064 nm激光则会独立诱导损伤，耦合效应不明显。 研究了三倍频分离膜在355 nm，532 nm和1064 nm激光单独或共同作用下的损伤特性。在355 nm和1064 nm激光耦合损伤研究中发现两个新现象，一是形貌研究中，1064 nm激光诱导的膜层剥落面积大小与355 nm的能量大小有关系，初步的解释认为，355 nm激光诱导薄膜发生损伤时产生的等离子体会强烈促进后续1064 nm激光的吸收，损伤越大、等离子体越多、吸收的1064 nm激光能量也就越大；另一个现象是在损伤阈值的测试结果中发现，小能量的1064 nm对薄膜有激光预处理效应。为了分析这两个现象，控制1064 nm激光相对355 nm激光提前或延迟一段时间辐照薄膜，实验现象进一步验证了上述理论。 采用人工预置纳米颗粒小球于基底上的方法分析了355 nm高反射膜中节瘤缺陷的影响。结果发现，在355 nm激光作用下，大的节瘤会出现喷射而小的节瘤只会在膜层表面上节瘤球冠边缘处发生损伤；而且随着节瘤种子的增大，薄膜的损伤阈值也不断降低。 |
| 英文摘要 | Thin film beam splitters, which are designed to reflect the harmonic wavelength of combined lasers while transmitting other parts, play an important role in frequency converting system because they can be used as harmonic wavelength separation device. In order to improve the laser-induced damage threshold (LIDT) of beam splitters, the damage performance under simultaneous irradiation of different lasers was investigated and the damage mechanisms were also explored. Damage morphologies and LIDTs of the second harmonics splitters were obtained when the coatings were irradiated by 532 nm laser only, 1064 nm laser only and the two lasers simultaneously..The different damage morphologies induced by 532 nm and 1064 nm lasers indicate that the damage mechanisms for the two lasers were totally different. In order to determine the coupling efficiency between the two lasers, 532 nm LIDTs were measured when different 1064 nm laser fluence were added. It was found that 1064 nm laser at low fluence would couple with the 532 nm laser and promote the damage initiation; however, 1064 nm laser at high fluence caused damages independently during the same pulse. The damage performance of the third harmonics splitters when they were irradiated by 355 nm, 532 nm and 1064 nm lasers only or combined lasers of 355 and 1064 nm lasers were also studied. Two special phenomena were found when the coatings were under the simultaneous irradiation of 355 and 1064 nm lasers. One is that the diameters of delamination, which was induced by 1064 nm laser, depended on 355 nm laser fluence in the coupling damages. A possible explanation was proposed that plasma produced with the 355 nm laser-induced damage initiation can absorb the following 1064 nm pulse energy more effectively than solid materials. The other is that 1064 nm laser at low fluence had laser conditioning effect. Further investigations when the 1064 nm pulses arrived at the samples earlier or later than the 355 nm pulses were made, and the experimental results confirmed the explanation. Nodules grown from the artificial seeds in the 355 nm high reflectivity coatings were studied, too. With the increase of seed diameters, the LIDT decreased. Moreover, large nodules in this coating can eject while the small nodules can only cause damages at the edge of spherical crown. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16712]  |
| 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 | 严磊. 波长分离膜在多波长激光辐照下的损伤特性研究[D]. 中国科学院上海光学精密机械研究所. 2012. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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