Browsing by Author "Cheng, C. W."

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Ablation of copper by a scanning Gaussian beam of a femtosecond laser pulse
(2017-09-01)
Cheng, C. W.
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機械工程學系
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Department of Mechanical Engineering
This study investigated ablation from a copper metal surface using a scanning femtosecond laser beam with a Gaussian beam profile. A method was developed herein to calculate the ablation profile with experimentally identified parameters (e.g., effective focused Gaussian incident beam radius, ablation threshold fluence, effective energy penetration depth). The results show the relationship between the maximum ablation depth and maximum ablation width. The calculated ablation profile agrees well with the experimental measurements.
Ablation of Copper by a Single Ultrashort Laser Pulse
(2014-06-01)
Wang, S. Y.
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Ren, Y. P.
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Chang, K. P.
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Cheng, C. W.
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Chen, J. K.
Thermal ablation of copper films by a single Ti:Sapphire femtosecond laser pulse of wavelength 800 nm and duration 100 fs was investigated experimentally and theoretically. The laser experiments were performed; the ablation depth and crater profiles were measured for laser fluences up to 1037 J/cm(2). A comprehensive axisymmetric model, including a two-temperature model, phase change models for rapid melting and evaporation, and a phase explosion model for ejecting metastable liquid and vapor, was developed to simulate the laser material ablation process. The simulated ablation depths and crater profiles agree well with the experimental measurements.
Femtosecond laser ablation of copper at high laser fluence: Modeling and experimental comparison
(2016-01-15)
Cheng, C. W.
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Wang, S. Y.
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Chang, K. P.
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Chen, J. K.
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機械工程學系
Thermal ablation of a copper foil surface by a single femtosecond laser pulse of duration 120 fs and wavelength 800 nm was investigated herein both theoretically and experimentally. A 1D two-temperature model with temperature-dependent material properties was considered, including the extended Drude model for dynamic optical properties. The rapid phase change and phase explosion models were incorporated to simulate the material ablation process. The simulated ablation depths agree well with the experimental measurements for the high laser fluence regime ranging from 6.1 to 63.4 j/cm(2). (C) 2015 Elsevier B.V. All rights reserved.
Femtosecond laser processing of indium-tin-oxide thin films
(2015-06-01)
Cheng, C. W.
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Lee, I. M.
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Chen, J. S.
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機械工程學系
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Department of Mechanical Engineering
Micro- and nano-scale crystalline indium-tin-oxide (c-ITO) patterns fabricated from amorphous ITO (a-ITO) thin films on a glass substrate using a (low NA 0.26) femtosecond laser pulse that is not tightly focused are demonstrated. Different types of c-ITO patterns are obtained by controlling the laser pulse energies and pulse repetition rate of a femtosecond laser beam at a wavelength of 1064 nm: periodic micro c-ITO dots with diameters of similar to 1.4 mu m, two parallel c-ITO patterns with/without periodic-like glass nanostructures at a laser scanning path and nano-scale c-ITO line patterns with a line width similar to 900 nm, i.e. similar to 1/8 of the focused beam\'s diameter (7 mu m at 1/e(2)). (C) 2015 Elsevier Ltd. All rights reserved.
Femtosecond laser sintering of copper nanoparticles
(2016-04)
Cheng, C. W.
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Chen, J. K.
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機械工程學系
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Department of Mechanical Engineering
The ultrafast melting of copper nanoparticles (NPs) induced by a femtosecond laser pulse with duration of 100 fs and wavelength of 800 nm is investigated theoretically and experimentally. The Cu pattern fabricated from sintering of a Cu NP-dispersed film by the femtosecond laser at a repetition rate of 80 MHz is experimentally studied. A one-dimensional two-temperature model with temperature-dependent material properties, including the extended Drude model for dynamic optical properties and the thermophysical properties, is employed to simulate the particles ultrafast melting and re-solidification process.
Femtosecond laser-induced nanoperiodic structures and simultaneous crystallization in amorphous indium-tin-oxide thin films
(2014-10-15)
Cheng, C. W.
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Lee, I. M.
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Chen, J. S.
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機械工程學系
;
Department of Mechanical Engineering
Fabrication of crystalline indium-tin-oxide (c-ITO) nanogratings and smooth line patterns on amorphous ITO (a-ITO) thin films by femtosecond laser-induced structuring and simultaneous crystallization followed by chemical etching is demonstrated. Three types of c-ITO structures are obtained merely by controlling the laser pulse energy of a high-repetition rate femtosecond laser at wavelength 532 nm: nanogratings perpendicular to laser polarization direction with period of 130 perpendicular to 11 nm, smooth c-ITO line patterns as well as nanogratings parallel to laser polarization direction with period of 390 +/- 10 nm. Large area c-ITO patterns and nanograting structures are fabricated, which are expected to be used in optoelectronic and micro-electronic devices. (C) 2014 Elsevier B.V. All rights reserved.