Femtosecond laser ablation of silicon in air and vacuum

Femtosecond(fs) pulse laser ablation of silicon targets in air and in vacuum is investigated using a timeresolved shadowgraphic method. The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum. Similar to the ablation of metallic targets,while the shock wave front and a series of nearly concentric and semicircular stripes,as well as the contact front,are clearly identifiable in the process of ablation under 1×10 5 Pa,these phenomena are no longer observed when the ablation takes place in vacuum. Although the ambient air around the target strongly affects the evolution of the ablation plume,the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum. It is proven that the three rounds of material ejection are caused by different ablation mechanisms.     

瑞斯尼克、哈里德著《物理学》第四版简介

瑞斯尼克、哈里德著《物理学》第四版简介吴泽华（浙江大学物理系杭州３１００２７）美国瑞斯尼克（ＲｏｂｅｒｔＲｅｓｎｉｃｋ）和哈里德（ＤａｖｉｄＨａｌｉｄａｙ）合著的《物理学》，是一套在美国高等院校较为普遍采用的物理学教材．它初版于１９６０年，经过三次修...     

电磁力与惯性力的相似性研究

无外场时,转动参照系中的物体受到惯性离心力、科里奥利力和横向力的作用。转动参照系中的惯性离心力与运动电荷受到的电场力等价,两者都是保守力;科里奥利力与磁场力等价,两者都不改变运动物体的动能;而转动参照系中的横向力与惯性系中的感应电场力类似。研究结果表明力学与电磁学具有相似性,相对性原理是正确的。     

物理教育研究与物理教学——访问美国华盛顿大学物理教育研究组

位于美国西海岸北部，风景秀丽的西雅图的华盛顿大学，是一所有一百三十条年历史，享有很高学术声誉和优良教育传统的著名高等学府。该校物理系的物理教育研究组拥有一支力量雄厚的物理教育研究队伍，有长期致力于教育研究的专家(在职的与退休的)，六位教育研究博士生，以及一位博士后。研究课题得到了美国国家科学基金委员会的资助。     

Time-resolved shadowgraphs and morphology analyses of aluminum ablation with multiple femtosecond laser pulses

Aluminum ablation by multiple femtosecond laser pulses is investigated via time-resolved shadowgraphs and scanning electron microscope(SEM) images of the ablation spot. The spatial distribution of the ejected material and the radius of the shock wave generated during the ablation are found to vary with the increase in the number of pulses. In the initial two pulses, nearly concentric and semicircular stripes within the shock wave front are observed, unlike in subsequent pulses. Ablation by multiple femtosecond pulses exhibits different characteristics compared with the case induced by single femtosecond pulse because of the changes to the aluminum target surface induced by the preceding pulses.     

大学物理实验教学与研究

在美国的基础物理教学中十分重视实验救学，从西雅图华盛顿大学的实验课程设置及教学研究情况可以反映美国大学的一般情况。