聚焦激光束焦点光斑尺寸与样品剥离阈值的同时测量

Simultaneous Determination of Spot Size of Focused Laser Beam on Focal Plane and Laser-Ablation Thresholds of Samples

当聚焦激光束在焦平面上的光强分布为高斯分布时,理论推导了激光能量与激光在样品表面所烧蚀的坑洞半径的关系。以铝箔、铝反射镜和热敏相纸为样品,用显微镜测量出不同能量的脉冲激光在样品表面烧蚀的坑洞半径并通过数值拟合来实现对聚焦激光束的焦点光斑尺寸和样品剥离阈值的同时测量。对于脉宽为15ns、波长为532nm的激光,测得铝和热敏相纸的剥离阈值分别为2.5J/cm2和0.25J/cm2。光斑尺寸和剥离阈值两个参量的测量误差均约为±10%。该技术能够同时且简便地测量出聚焦激光束焦点的光斑尺寸和样品的剥离阈值,对研究固体与激光相互作用以及评价激光束聚焦的特性有一定的应用价值。

The function of laser pulse energy to the radius of the crater produced by focused laser beam on sample′s surface is derived theoretically under the condition that the fluency distribution of the focused laser beam on the focal plane is Gaussian shape.An aluminum foil,an aluminum reflection mirror and a piece of thermo-sensitive photographic paper are used as samples and the radii of the craters produced by laser beam with different pulse energies on sample′s surfaces are measured with a microscope.The spot size of focused laser beam on the focal plane and the laser-ablation threshold of the sample are measured simultaneously by curve fitting.The laser-ablation thresholds of aluminum and thermo-sensitive photographic paper for 532 nm laser pulse with 15 ns pulse width are determined to be 2.5 J/cm^2 and 0.25 J/cm^2,respectively.Measurement errors for both spot size and laser-ablation threshold are about ±10%.It is demonstrated that the approach introduced here is able to determine spot size of the focused laser beam on the focal plane and the laser-ablation threshold of the sample conveniently and simultaneously.It is able to be used in researches on laser interaction with solid materials and to evaluate the characterization of a focused laser beam.