Glass products with precise and sophisticated shapes are highly demanded in the field of MEMS due to their excellent properties. Ultrashort pulsed laser has been expected to be a powerful and reliable tool for micro-welding of glass. Focusing condition such as numerical aperture (N.A.) is a critical parameter that controls how ultrashort laser pulses interact with and propagate in glass, and it has a great influence on the laser micro-welding characteristics of glass. In order to investigate the quality of welding process, it is important to understand the dependence of the mechanical strength of molten area created in glass specimen with various numerical apertures. Therefore, the mechanical strength of molten area with various numerical apertures was evaluated in micro-welding of glass by picosecond pulsed laser. Higher bending strength could be obtained under an appropriate volume ratio of molten area and glass specimen, when continuous molten areas were formed. In addition, high density and large size of molten area without crack led to higher breaking stress. It is concluded that superior focusing characteristics such as N.A. 0.65 enable a long region of high power density in beam axis, which can satisfy both high mechanical strength and high processing speed.

中文翻译：

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皮秒脉冲激光中数值孔径对玻璃微连接中熔融面积特性的影响

由于其优异的性能，在MEMS领域对形状精确且精密的玻璃产品提出了很高的要求。人们期望超短脉冲激光是用于玻璃微焊接的强大而可靠的工具。聚焦条件（例如数值孔径（NA））是控制超短激光脉冲如何与玻璃相互作用和在玻璃中传播的关键参数，并且对玻璃的激光微焊接特性有很大影响。为了研究焊接工艺的质量，重要的是要了解在具有各种数值孔径的玻璃样品中产生的熔融区域的机械强度的依赖性。因此，在通过皮秒脉冲激光对玻璃进行微焊接时，对具有各种数值孔径的熔融区域的机械强度进行了评估。当形成连续的熔融区域时，在适当的熔融区域和玻璃试样的体积比下可以获得更高的弯曲强度。另外，高密度和大尺寸的熔融区域而无裂纹导致较高的断裂应力。结论是，NA 0.65等优异的聚焦特性可以使光束轴在较长的区域内具有高功率密度，从而可以同时满足高机械强度和高加工速度。