Analysis for laser spot image under the condition of femtosecond laser beam error

• Published in: Optics communications Vol. 433; pp. 268 - 274
• Main Authors: Wang, Fu-bin, Sun, Hai-yang, Zeng, Kai, Chen, Jian-xiong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2019
• Subjects: Ablated spot image; Femtosecond laser; Image analysis of ablated spot; Laser beam error; Laser beam error; Femtosecond laser; Ablated spot image; Image analysis of ablated spot
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2018.10.029

In the process of using femtosecond laser to ablate crystal silicon wafer, plasma diffraction spot phenomenon occurs accompanied by ablated material vaporization. To explore the role of spot image in the femtosecond laser processing, the relationship between spot characteristics and the laser ablation power is studied. In this paper, for the problem that the laser beam of femtosecond laser machining center deviating from the ideal position, the change relationship between spot image characteristics and the ablation power is analyzed. First of all, through femtosecond laser ablation experiment with silicon wafer, the image of position deviation between the ideal laser beam focus and the actual laser beam focus is obtained; analysis shows that, although the trailing direction of ablated plasma spot has changed along with the round-trip movement of the workbench, the relative position between the ideal laser beam focus and the ablated spot center is basically the same, which can be considered approximate systematic error. Secondly, the three-dimensional relative energy distribution and corresponding transverse or longitudinal section of spot image under the condition of 50mW ablation power are studied; It is found that, although the trailing direction of the spot is different, the ablation energy and ablation effect changed little under the established laser output power condition, thus the stability of laser ablation process and the geometric size ablated structure are ensured. Finally, the relationship between ablation power and pixel area of single point spot, width to height ratio of external rectangle are studied, we found that the size of ablated pixel area of spot increases linearly with the increase of ablation power, which shows that, in spite of the position error of the beam, the workbench can still meet the requirements for machining precision. ) •The works in this paper have reference values for micromachining by femtosecond laser.•Although the trailing direction of ablated plasma spot has changed along with the round-trip movement of the workbench, the relative position between the ideal laser beam focus and the ablated spot center is basically the same, which can be considered approximate systematic error.•Although the trailing direction of the spot is different, the ablation energy and ablation effect changed little under the established laser output power condition, thus the stability of laser ablation process and the geometric size ablated structure are ensured.•The relationship between ablation power and pixel area of single point spot, width to height ratio of external rectangle are studied, we found that the size of ablated pixel area of spot increases linearly with the increase of ablation power, which shows that, in spite of the position error of the beam, the workbench can still meet the requirements for machining precision.