查看更多>>摘要：The micro-bumps of metal films induced by ultrafast laser have potential applications in various fields, such as biotechnology and energy, etc. The mechanism of micro-bump deformation of the gold film irradiated by single ultrafast laser pulse is controversial. In this study, the experimental research of single ultrafast laser pulse irradiating gold films with different thicknesses from 20 nm to 200 nm is carried out, with the laser fluence varying from 1 to 50 J/cm(2). The micro-bumps without melting are observed by the Scanning Electron Microscope (SEM) and different separation thresholds can be obtained. The separation threshold of gold films ranges from 5.1 to 43.5 J/cm(2) and it increases with the thickness of gold film increasing. The heights of micro-bumps are measured by Atomic Force Microscope (AFM). One-dimension (1D) Molecular dynamic (MD) simulations are carried out to analyze the temperature and stress evolutions. Large-scale two-dimension (2D) MD simulations are furthermore performed to obtain the micro-bump structure. MD simulations showing a good agreement with experiments, and the essential mechanism responsible for micro-bump without melting is clearly analyzed. It is also analyzed that the heights of micro-bumps are related to the laser fluences and radii of spot.
Villareal, Mark Roan ElraeBinamira, JonelAlmoro, Percival
6页
查看更多>>摘要：Stagnation errors in iterative smooth object wavefront reconstruction occur because of insufficient intensity variation despite employing experimental methods that increase intensity variation such as the use of multiple illumination wavelengths. In this study, an algorithmic technique for optimized multiple wavelength phase retrieval that uses wavelength-to-distance transformation and unordered wave propagations sequence is demonstrated. Simulations show that the technique significantly accelerates the reconstruction compared to conventional methods based on sequential propagations. The number and tuning range (or spacing) of the illumination wavelengths are also optimized resulting in the enhanced reconstruction of the test object waves used. The main advantage of the technique is the reduced number of illumination wavelengths needed for enhanced object wave reconstruction.
NSTL
Elsevier