Determination of Cross-Sectional Area of Focused Picosecond Gaussian Laser Beam

Ledesma, Rodolfo ; Fitz-Gerald, James ; Palmieri, Frank ; Connell, John

关键词: LASER ABLATION;    SURFACE ROUGHNESS;    SCANNING ELECTRON MICROSCOPY;    PULSED LASERS;    FLUENCE;    PULSE DURATION;    LASERS;    TARGETS;    SUBSTRATES;    ABLATION;   

RP-ID  :  NASA/TM-2018-219809,L-20906,NF1676L-29237

学科分类：原子、分子光学和等离子物理

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

Measurement of the waist diameter of a focused Gaussian-beam at the 1/e(sup 2) intensity, also referred to as spot size, is key to determining the fluence in laser processing experiments. Spot size measurements are also helpful to calculate the threshold energy and threshold fluence of a given material. This work reports an application of a conventional method, by analyzing single laser ablated spots for different laser pulse energies, to determine the cross-sectional area of a focused Gaussian-beam, which has a nominal pulse width of approx. 10 ps. Polished tungsten was used as the target material, due to its low surface roughness and low ablation threshold, to measure the beam waist diameter. From the ablative spot measurements, the ablation threshold fluence of the tungsten substrate was also calculated.