Internal modification of glass by ultrashort laser pulse and its application to microwelding
Internal modification of glass by ultrashort laser pulse and its application to microwelding
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DOI：
10.1007/s00339-013-8115-3
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
I. Miyamoto;K. Cvecek;Y. Okamoto;Michael Schmidt
中科院分区：
文献类型：
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作者：
I. Miyamoto;K. Cvecek;Y. Okamoto;Michael Schmidt
介绍了超短激光脉冲对玻璃进行内部改性的工艺及其在玻璃微焊接中的应用。建立了一个仿真模型，可以确定不同脉冲重复率和脉冲能量下，用实验修饰结构的fs-和ps-激光脉冲对体玻璃进行内部修饰时，吸收激光能量的强度分布、非线性吸收率和温度分布。阐明了双结构内改性的形成过程，双结构内改性由泪滴形状的内部结构和椭圆形的外部结构组成，分别对应于激光吸收区和热影响熔融区。由于雪崩电离的热激发自由电子密度的增加，高脉冲重复率下的非线性吸收率增加。USLP通过非线性吸收过程产生埋埋熔池，抑制了收缩应力，从而实现了玻璃的无裂纹焊接，而传统的连续波激光焊接由于冷却过程中产生的收缩应力而无法避免裂纹。利用USLP技术开发了玻璃微焊接技术，利用光学接触样品对连接玻璃/玻璃和硅/玻璃。在玻璃/玻璃焊接中，无需预加热和后加热即可获得与母材相同的焊缝强度。在硅/玻璃焊接中，在连接强度和工艺吞吐量方面获得了与阳极键合相媲美的优异连接性能。
Internal modification process of glass by ultrashort laser pulse (USLP) and its applications to microwelding of glass are presented. A simulation model is developed, which can determine intensity distribution of absorbed laser energy, nonlinear absorptivity and temperature distribution at different pulse repetition rates and pulse energies in internal modification of bulk glass with fs- and ps-laser pulses from experimental modified structure. The formation process of the dual-structured internal modification is clarified, which consists of a teardrop-shaped inner structure and an elliptical outer structure, corresponding to the laser-absorbing region and heat-affected molten region, respectively. Nonlinear absorptivity at high pulse repetition rates increases due to the increase in the thermally excited free electron density for avalanche ionization. USLP enables crack-free welding of glass because the shrinkage stress is suppressed by producing embedded molten pool by nonlinear absorption process, in contrast to conventional continuous wave laser welding where cracks cannot be avoided due to shrinkage stress produced in cooling process. Microwelding techniques of glass by USLP have been developed to join glass/glass and Si/glass using optically contacted sample pairs. The strength of the weld joint as high as that of base material is obtained without pre- and post-heating in glass/glass welding. In Si/glass welding, excellent joint performances competitive with anodic bonding in terms of joint strength and process throughput have been attained.