Critical femtosecond laser parameters for the fabrication of optimal reflecting diffraction gratings on Invar36

2016 ◽  
Vol 81 ◽  
pp. 97-102 ◽  
Author(s):  
Goudarzi Mohammad Hossein ◽  
Lin Meng-Jyun ◽  
Horng Ji-Bin ◽  
Jeng Jeng-Ywan
Keyword(s):  
Femtosecond Laser ◽  
Diffraction Gratings ◽  
Laser Parameters

scholarly journals Femtosecond Laser Drilling of Cylindrical Holes for Carbon Fiber-Reinforced Polymer (CFRP) Composites

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2953
Author(s):  
Hao Jiang ◽  
Caiwen Ma ◽  
Ming Li ◽  
Zhiliang Cao
Keyword(s):  
Carbon Fiber ◽  
Femtosecond Laser ◽  
Picosecond Laser ◽  
Laser Drilling ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Laser Parameters ◽  
Reinforced Polymer ◽  
Cfrp Composites ◽  
Cylindrical Holes

Ultrafast laser drilling has been proven to effectively reduce the heat-affected zone (HAZ) of carbon fiber-reinforced polymer (CFRP) composites. However, previous research mainly focused on the effects of picosecond laser parameters on CFRP drilling. Compared with a picosecond laser, a femtosecond laser can achieve higher quality CFRP drilling due to its smaller pulse width, but there are few studies on the effects of femtosecond laser parameters on CFRP drilling. Moreover, the cross-sectional taper of CFRP produced by laser drilling is very large. This paper introduces the use of the femtosecond laser to drill cylindrical holes in CFRP. The effect of laser power, rotational speed of the laser, and number of spiral passes on HAZ and ablation depth in circular laser drilling and spiral laser drilling mode was studied, respectively. It also analyzed the forming process of the drilling depth in the spiral drilling mode and studied the influence of laser energy and drilling feed depth on the holes’ diameters and the taper. The experimental results show that the cylindrical hole of CFRP with a depth-to-diameter ratio of about 3:1 (taper < 0.32∘, HAZ < 10 m) was obtained by using femtosecond laser and a spiral drilling apparatus.

scholarly journals Study of the formation of 3-D titania nanofibrous structure by MHz femtosecond laser in ambient air

2021 ◽  
Author(s):  
Amirhossein Tavangar ◽  
Bo Tan ◽  
Krishnan Venkatakrishnan
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Deposition Rate ◽  
Femtosecond Laser Ablation ◽  
Ambient Air ◽  
Experimental Results ◽  
Laser Parameters ◽  
Nanofibrous Structure ◽  
Titania Nanostructures ◽  
Multiple Pulses

In this study, we describe the formation mechanism of web-like three-dimensional (3-D) titania nanofibrous structures during femtosecond laser ablation of titanium (Ti) targets in the presence of background air. First, we demonstrate the mechanism of ablation of Ti targets by multiple femtosecond laser pulses at ambient air in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles, which is analogous to the deposition rate of the synthesized nanofibers, for the ablation by a single pulse and multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Afterwards, the formation of nanofibrous structures is demonstrated by applying an existing simplified kinetic model to Ti targets and ambient conditions. The predicted theory provides nanofiber diameter dependency with the combination of laser parameters, target properties, and ambient gas characteristics. Experimental studies are then performed on titania nanofibrous structures synthesized by laser ablation of Ti targets using MHz repletion-rate femtosecond laser at ambient air. The models' predictions are then compared with the experimental results, where nanostructures with different morphologies are manufactured by altering laser parameters. Our results indicate that femtosecond laser ablation of Ti targets at air background yields crystalline titania nanostructures. The formation of crystalline titania nanostructures is preceded b thermal mechanism of nucleation and growth. The results point out that laser pulse repetition and dwell time can control the density, size, and pore size of the engineered nanofibrous structure. As the deposition rate of nanostructures is analogous to the ablation rate of the target, higher density of nanofibrous structure is seen at greater laser fluences. The predicted theory can be applied to predict ablation mechanism and nanofiber formation of different materials.

scholarly journals Influence of laser parameters and staining on femtosecond laser-based intracellular nanosurgery

2010 ◽  
Vol 1 (2) ◽  
pp. 587 ◽  
Author(s):  
K. Kuetemeyer ◽  
R. Rezgui ◽  
H. Lubatschowski ◽  
A. Heisterkamp
Keyword(s):  
Femtosecond Laser ◽  
Laser Parameters

scholarly journals Micro/Nano Amorphization/Oxidation Of Silicon Induced By High Repetition Femtosecond Laser Pulses

2021 ◽  
Author(s):  
Amirkianoosh Kiani
Keyword(s):  
Solar Cell ◽  
Femtosecond Laser ◽  
Surface Temperature ◽  
Pulse Duration ◽  
Analytical Model ◽  
Repetition Rate ◽  
Crystalline Silicon ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Laser Parameters

The main aim of this thesis is to develop a new method for direct micro/nano amorphization/oxidation of silicon using femtosecond laser irradiation and its applications in maskless lithography and solar cell fabrication. Amorphization and oxidation occur when crystalline silicon is exposed to the irradiation of femtosecond laser pulses below the ablation threshold. Mechanisms of morphization and oxidation were discussed and the surface temperature model was developed to study the relation between laser parameters and observed amorphization and oxidation. A systematic theoretical and experimental study of the influence of the laser parameters on the quality of amorphorized area and the size of the feature fabricated through amorphization has been studied. It was found that during the process of silicon amorphization and oxidation, the higher repetition rate of laser pulses yields smooth morphology with better repeatability. Increasing pulse duration and number of pulses were seen to increase the line width. However, increasing the number of pulses does not result in ablation of the target area. An analytical model was developed for the calculation of the average surface temperature after n-pulses. The effect of the laser pulse width was investigated by developing an analytical model for the calculation of the non-dimensional surface temperature with various pulse widths. It was found from experimental and analytical results that for a constant power and repetition rate, an increase in the pulse duration corresponds to a significant increase in the surface temperature. It results in an increase in the amount of modified material as well as improvement of light absorption in the case of amorphization. The main aim of this thesis is to develop a new method for direct micro/nano amorphization/oxidation of silicon using femtosecond laser irradiation and its applications in maskless lithography and solar cell fabrication.Amorphization and oxidation occur when crystalline silicon is exposed to the irradiation of femtosecond laser pulses below the ablation threshold. Mechanisms of morphization and oxidation were discussed and the surface temperature model was developed to study the relation between laser parameters and observed amorphization and oxidation. A systematic theoretical and experimental study of the influence of the laser parameters on the quality of amorphorized area and the size of the feature fabricated through amorphization has been studied. It was found that during the process of silicon amorphization and oxidation, the higher repetition rate of laser pulses yields smooth morphology with better repeatability. Increasing pulse duration and number of pulses were seen to increase the line width. However, increasing the number of pulses does not result in ablation of the target area. An analytical model was developed for the calculation of the average surface temperature after n-pulses.The effect of the laser pulse width was investigated by developing an analytical model for the calculation of the non-dimensional surface temperature with various pulse widths. It was found from experimental and analytical results that for a constant power and repetition rate, an increase in the pulse duration corresponds to a significant increase in the surface temperature. It results in an increase in the amount of modified material as well as improvement of light absorption in the case of amorphization.The amorphous silicon and silicon oxide can act as an etch stop. Therefore, maskless lithography iis possible with the direct patterning (amorphization and oxidation) of crystalline silicon. Experimental results have proved the feasibility of the proposed concepts. The thin-film of amorphous silicon generated on the silicon substrate has a potential for use in photovoltaic devices and solar cell fabrication. In comparison with previous methods, the direct oxidation/amorphization of silicon induced by the femtosecond laser is a maskless single-step technique which offers a higher flexibility and reduced processing time.

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