飞秒平顶光束经微透镜阵列在熔融石英中的成丝及其超连续辐射  

Filamentation and supercontinuum emission with flattened femtosecond laser beam by use of microlens array in fused silica

作　　者：周宁 张兰芝 李东伟 常峻巍 王毕艺[2] 汤磊 林景全[1] 郝作强[1] Zhou Ning;Zhang Lan-Zhi;Li Dong-Wei;Chang Jun-Wei;Wang Bi-Yi;Tang Lei;Lin Jing-Quan;Hao Zuo-Qiang(School of Science,Changchun University of Science and Technology,Changchun 130022,China;cience and Technology on Electro-Optical Information Security Control Laboratory,Tianjin 300308,China;China Research and Development Academy of Machinery Equipment,Beijing 100089,China)

机构地区：[1]长春理工大学理学院,长春130022 [2]光电信息控制和安全技术重点实验室,天津300308 [3]中国兵器科学研究院,北京100089

出　　处：《物理学报》2018年第17期130-135,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11474039;11774038;11274053);吉林省科技厅项目(批准号:20170519018JH);长春理工大学科技创新基金(批准号:XJJLG-2016-02)资助的课题~~

摘　　要：实验研究了平顶激光光束经微透镜阵列在熔融石英中成丝的演化以及超连续辐射的产生,并进一步与高斯光束的成丝和超连续辐射进行了对比研究.分别对这两种光束的多丝传输进行了横向和纵向成像.结果表明,使用平顶光束可以获得更为均匀的多丝分布,成丝的起点也更为一致;尤其重要的是,相对于高斯光束,平顶光束可以使用更高的入射激光脉冲能量而不会造成介质的损伤,从而可以获得更高脉冲能量和更高转换效率的超连续辐射.The high power supercontinuum from femtosecond filamentation has attracted great attention for recent years due to its various applications. In our previous researches, we have used microlens array to obtain filament-array in fused silica and to generate the high spectral power supercontinuum. To further improve the ability to generate the high power supercontinuum by using microlens array, in this work we adopt flattened femtosecond laser beam with a flat-top energy distribution to generate filament-array in fused silica and supercontinuum. By using a laser beam shaping system consisting of aspherical lenses, the Gaussian intensity distribution of initial femtosecond laser beam is converted into a flat-top distribution. The flattened laser beam is focused by a microlens array into a fused silica block, and consequently a filament array is formed in the block. Our experimental results show that compared with the filaments formed by a Gaussian laser beam, the filaments formed by the flattened beam have a uniform distribution and almost the same onset due to the initial uniform energy distribution across the section of the laser beam. Furthermore, the spectral stability of supercontinuum emission is used to evaluate the damage of the fused silica block. It is demonstrated that the flattened beam with a pulse energy of 1.9 m J does not induce permanent damage to the fused silica block, while the Gaussian beam with a relatively low pulse energy of 1.46 m J leads to the damage to the block. Therefore, a higher incident laser pulse energy is allowed in the case of flattened laser beam, and consequently stronger supercontinuum generation than in the case of the Gaussian laser beam can be expected. In our experiments, the relative spectral intensity of flattened beam generated supercontinuum in the visible range is about twice higher than that for the Gaussian beam case. The conversion efficiencies of the supercontinuum for the two kinds of laser beams are further analyzed. The conversion efficiencies are 49% and 55% for

关 键 词：激光成丝 平顶光束 超连续辐射产生 微透镜阵列 

分 类 号：TN24[电子电信—物理电子学]