Zhang Guodong, Stoian Razvan, Zhao Wei, Cheng Guanghua
Opt Express. 2018 Jan 22;26(2):917-926. doi: 10.1364/OE.26.000917.
It is known that ultrashort laser welding of materials requires an accurate laser beam focusing and positioning onto the samples interface. This puts forward severe challenges for controlling the focus position particularly considering that the tightly focused Gaussian beam has a short, micron-sized Rayleigh range. Here we propose a large-focal-depth welding method to bond materials by using non-diffractive femtosecond laser Bessel beams. A zero-order Bessel beam is produced by an axicon and directly imaged on the interface between silicon and borosilicate glass to write welding lines, ensuring a non-diffractive length in the 500 μm range and micron-sized FWHM diameter. The focal-position tolerant zone for effective welding increases thus many-fold compared to traditional Gaussian beam welding. The shear joining strength of the sample welded by this method could be as high as 16.5 MPa. The Raman spectrum and element distribution analyses within the cross section of welding line reveal that substance mixing has occurred during laser irradiation, which is considered as the main reason for femtosecond laser induced bonding.
众所周知，材料的超短激光焊接需要将激光束精确聚焦并定位在样品界面上。这对聚焦位置的控制提出了严峻挑战，尤其是考虑到紧密聚焦的高斯光束具有短的、微米级的瑞利范围。在此，我们提出一种大焦深焊接方法，通过使用非衍射飞秒激光贝塞尔光束来连接材料。零阶贝塞尔光束由轴棱锥产生，并直接成像在硅和硼硅酸盐玻璃之间的界面上以写入焊接线，确保在500μm范围内的非衍射长度和微米级的半高宽直径。与传统高斯光束焊接相比，有效焊接的焦位容差区因此增加了许多倍。用这种方法焊接的样品的剪切连接强度可高达16.5MPa。焊接线横截面内的拉曼光谱和元素分布分析表明，激光辐照期间发生了物质混合，这被认为是飞秒激光诱导键合的主要原因。
