Shadi Davoudi, Somayeh Mehrabian,
Volume 16, Issue 1 (1-2022)
Abstract
In this study, the self-guiding of an ultrashort laser pulse through air is investigated. Therefore, the terms of self-focusing, plasma defocusing and the pulse energy depletion due to the ionization, are considered in the wave equation. Then the laser pulse spot size equation is obtained using the source-dependent expansion method. Our results show that the laser pulse self-guiding occurs for the first twenty Rayleigh lengths. However, the laser pulse undergoes diffraction as it propagates further along the z axis. Moreover, it is seen that the back of the laser pulse is diffracted the most owing to the fact that the plasma is formed as the laser pulse propagates through air. It is also shown that the spot size variations affect the temporal and spatial profiles of the laser intensity, the laser pulse power and the ionization process.
Masume Moshkelgosha, Fatemeh Asem_abadi, Hajar Tavakoli,
Volume 17, Issue 1 (1-2023)
Abstract
The creation of single zeptosecond pulses is important in various scientific fields, particularly for studying time-resolved nuclear processes. In this study, a clean single sub-attosecond (270 zeptosecond) pulse is obtained in the simulation of a femtosecond laser with over dense plasma. First, the desired laser and plasma parameters are utilized to achieve the nano-bunches in the plasma surface and the desired spectrum up to 2000th harmonics is obtained. Then, different filters such as filtering the harmonics and different intensity filters are applied where, the special exponential function is due to a very clean single zeptosecond pulse.
Sajjad Aghajari, Mohammadmehdi Jahanbakhshian, Rouhollah Karimzadeh,
Volume 17, Issue 1 (1-2023)
Abstract
One of the basic requirements in the fabrication of microfluidic (MF) and optofluidic (OF) chips is a suitable initial mold, which is generally prepared with the help of a photoresist material. In this research, we investigate the SPE-60 photoresist as a quality alternative to the conventional SU-8 photoresist to achieve molds with thicknesses ranging from 25μm to 130μm and address the challenges of mold-making with this photoresist. The conventional photolithography method is used to assess the material's ability in mold making. The results show that SPE-60 molds have vertical edges, clean facets, and edges, complete voids between different components, and demonstrate good pattern transfer from the photomask to the SPE-60 film at various thicknesses. This article also suggests some ways to improve accuracy and reduce edge scattering. As a result, based on the experimental results, SPE-60 can be considered a cost-effective and suitable alternative to SU-8 photoresist in the fabrication of MF and OF molds.
Sahar Sohrabi, Hedieh Pazokian, Mohsen Montazerolghaem,
Volume 17, Issue 2 (6-2023)
Abstract
Laser pulse overlapping (LPO) is an important factor affect the behavior of the laser treated surfaces. For laser surface treatment especially at high fluences, the laser beam must be focused to reach the desired fluence. Then laser beam or sample scanning in 2 directions is done to treat a surface area. In this paper, effect of the distance between laser treated lines (scanned in x direction) on the surface properties including morphological changes and wettability modifications of 304 stainless steel is investigated. The results show that the morphology and chemistry of the surface are influenced effectively by changing the overlap between laser treated line on the surface. Then, it should be considered as an important parameter in laser modification of a large surface with focused laser beam.
