Browsing by Author "Chen, Jinn-Kuen"

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Femtosecond laser melting of silver nanoparticles: comparison of model simulations and experimental results
(2018-05-01)
Cheng, Chung-Wei
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Chang, Chin-Lun
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Chen, Jinn-Kuen
;
Wang, Ben
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機械工程學系
Ultrafast laser-induced melting of silver nanoparticles (NPs) using a femtosecond laser pulse is investigated both theoretically and experimentally. The sintered Ag structure fabricated from printed Ag NP ink using femtosecond laser (1064 nm, 300 fs) irradiation is experimentally studied. A two-temperature model with dynamic optical properties and particle size effects on the melting temperature of Ag NPs is considered. The rapid phase change model is incorporated to simulate the Ag NPs' ultrafast laser-induced melting process, and a multi-shot melting threshold fluence predicted from the simulated single-shot melting threshold is developed.
Femtosecond laser-induced periodic surface structures of copper: Experimental and modeling comparison
(2019-03-01)
Chang, Chin-Lun
;
Cheng, Chung-Wei
;
Chen, Jinn-Kuen
;
機械工程學系
;
Department of Mechanical Engineering
This study compared the experimental and numerical results of femtosecond laser-induced periodic surface structures (LIPSS) produced on copper surface. The experiments were carried out using a fiber laser of duration 300 fs, wavelength 515 nm, and a repetition rate 100 kHz. The periods of LIPSS were obtained by 2D fast Fourier transform analysis of the SEM images, and the depths were measured with an Atomic force microscope. Numerical analysis was performed using a two-dimensional two-temperature model (TTM) along with a modified Drude-critical points model, periodic energy distribution, and the phase change and explosion models for material ablation. The simulation results are in fairly good agreement with the experimental measurements.
Ultrafast laser ablation of copper by GHz bursts
(2020-07-31)
Cheng, Chung-Wei
;
Chen, Jinn-Kuen
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機械工程學系
;
Department of Mechanical Engineering
The ablation of copper, using a 10 GHz burst ultrafast laser with a wavelength of 1030 nm, a pulse duration of 1 ps, a variable total laser fluence, and a number of sub-pulses per burst, is investigated theoretically. A two-temperature model with an extended Lorentz-Drude model for dynamic optical properties is used to simulate the melting and ablation process. Due to the heat accumulation from the preceding pulses, multipulse laser ablation could be advantageous over a single pulse. Moreover, the ablation performance can be maximized by properly selecting the pulse number, separation time, and energy in a laser burst. The numerical result shows that the present prediction is in fairly agreement with existing experimental result. Under the same total laser fluence of 32 J/cm(2), a 10 GHz burst laser with an optimized 128 sub-pulse can significantly enhance the ablation depth, 4.2 times that a single pulse does. It is found that the optimized ablation depth is a linear function of the total fluence of ultrafast laser bursts.