Ablation Dynamics of Silicon by Femtosecond Laser and the Role of Early Plasma

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
X. Zhao ◽  
Y. C. Shin
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Energy Transport ◽  
Femtosecond Laser Ablation ◽  
Heat Diffusion ◽  
Photon Absorption ◽  
Ablation Efficiency ◽  
Two Photon Absorption ◽  
Laser Fluences ◽  
Plasma Absorption

In this paper, the femtosecond laser ablation of silicon is investigated by a two-dimensional hydrodynamic model. The ablation depth of the silicon wafer ablated in air at different laser intensities is calculated, and the corresponding experimental measurements are carried out for validation. Two different ablation regimes have been identified by varying the laser fluence. While two-photon absorption dominates in the low fluence regime (<2 J/cm2), electron heat diffusion is a major energy transport mechanism at higher laser fluences (>2 J/cm2). The ablation efficiency first increases with the laser fluence, and reaches the peak value at the laser fluence around 8 J/cm2. It starts to drop when the laser fluence further increases, because of the early plasma absorption of the laser beam energy.

Ablation Dynamics of Silicon by Femtosecond Laser and the Role of Early Plasma

2013 ◽  
Author(s):  
Xin Zhao ◽  
Yung C. Shin
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Energy Transport ◽  
Femtosecond Laser Ablation ◽  
Heat Diffusion ◽  
Photon Absorption ◽  
Ablation Efficiency ◽  
Two Photon Absorption ◽  
Laser Fluences ◽  
Plasma Absorption

In this paper, the femtosecond laser ablation of silicon is investigated by a two-dimensional hydrodynamic model. The ablation depth of the silicon wafer ablated in air at different laser intensities is calculated, and the corresponding experimental measurements are carried out for validation. Two different ablation regimes have been identified by varying the laser fluence. While two-photon absorption dominates in the low fluence regime (< 2 J/cm2), electron heat diffusion is a major energy transport mechanism at higher laser fluences (> 2 J/cm2). The ablation efficiency first increases with the laser fluence, and reaches the peak value at the laser fluence around 8 J/cm2. It starts to drop when the laser fluence further increases, because of the early plasma absorption of the laser beam energy.

Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency

2015 ◽  
Vol 20 (2) ◽  
pp. 028004 ◽  
Author(s):  
Hu Chen ◽  
Jing Liu ◽  
Hong Li ◽  
Wenqi Ge ◽  
Yuchun Sun ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Fluence ◽  
Femtosecond Laser Ablation ◽  
Ablation Efficiency

Fabrication of Three-Dimensional Micro-Structures with Two-Photon Absorption by Femtosecond Laser

2006 ◽  
Vol 532-533 ◽  
pp. 568-571
Author(s):  
Ming Zhou ◽  
Hai Feng Yang ◽  
Li Peng Liu ◽  
Lan Cai
Keyword(s):  
Photonic Crystal ◽  
Femtosecond Laser ◽  
Detection System ◽  
Three Dimensional ◽  
Photon Absorption ◽  
Micro Fabrication ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photo Polymerization ◽  
System A

The photo-polymerization induced by Two-Photon Absorption (TPA) is tightly confined in the focus because the efficiency of TPA is proportional to the square of intensity. Three-dimensional (3D) micro-fabrication can be achieved by controlling the movement of the focus. Based on this theory, a system for 3D-micro-fabrication with femtosecond laser is proposed. The system consists of a laser system, a microscope system, a real-time detection system and a 3D-movement system, etc. The precision of micro-machining reaches a level down to 700nm linewidth. The line width was inversely proportional to the fabrication speed, but proportional to laser power and NA. The experiment results were simulated, beam waist of 0.413μm and TPA cross section of 2×10-54cm4s was obtained. While we tried to optimize parameters, we also did some research about its applications. With TPA photo-polymerization by means of our experimental system, 3D photonic crystal of wood-pile structure twelve layers and photonic crystal fiber are manufactured. These results proved that the micro-fabrication system of TPA can not only obtain the resolution down to sub-micron level, but also realize real 3D micro-fabrication.

A STUDY OF FEMTOSECOND LASER POLISHING OF CVD NANOPOLYCRYSTALLINE DIAMOND FILMS

2021 ◽  
pp. 2150023
Author(s):  
YU-XIAO CUI ◽  
PING GUO ◽  
XUEMING ZHU ◽  
YAN-LING TIAN ◽  
DA-WEI ZHANG ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Promising Technique ◽  
Laser Polishing ◽  
Laser Fluences ◽  
Fs Laser ◽  
The Mean

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50[Formula: see text]MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7[Formula: see text]J/cm2, at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84[Formula: see text]nm to 31.88[Formula: see text]nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7[Formula: see text]J/cm2, large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

Resonant effects in nonlinear photon absorption during femtosecond laser ablation of Nd-doped silicate glass

2012 ◽  
Vol 51 (29) ◽  
pp. 7039 ◽  
Author(s):  
Yadong Zhao ◽  
Lan Jiang ◽  
Juqiang Fang ◽  
Qianghua Chen ◽  
Xiaowei Li ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Silicate Glass ◽  
Femtosecond Laser Ablation ◽  
Photon Absorption
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