• Title/Summary/Keyword: Femtosecond laser

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Simulation of Laser Micro Patterning Process Using FEM (유한요소법을 이용한 레이저 미세 패터닝 공정 해석)

  • Lee J. H.;Kim B. H.;Lee J. K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.09a
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    • pp.54-58
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    • 2005
  • Femtosecond laser is the latest generation pulsed laser delivering shortest pulses. Any solid materials can be machined by it. Femtosecond laser micromachining allows highest precision and minimal heat influence within the workpiece. But due to the complex physical phenomena between the laser beam and the workpiece materials, it is very difficult to determine the optimal process conditions in the femtosecond laser micromachining. In this study, a method to simulate the femtosecond laser micromachining process was proposed. And femtosecond laser micro patterning processes of chromium thin film are simulated by the proposed method using a commercial FE code, LS-Dyna. Simulation results were compared with those of experiments.

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Space-selective Precipitation and Control of Functional Crystals in Glasses by a Femtosecond Laser

  • Qiu, Jianrong;Zhu, Bin;Dai, Ye
    • Ceramist
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    • v.10 no.3
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    • pp.91-97
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    • 2007
  • Femtosecond laser micro-processing received much attention in the past decade. The nature of ultra-short light-matter interaction permits femtosecond laser to overcome the diffraction limit and realize precise micro-processing. The ultrahigh light intensity of the femtosecond laser allows sapece-selective microscopic modifications to materials based on multiphoton processes. In this paper, we review our recent research development on space-selective precipitation and control of functional crystals in glasses by an infrared femtosecond laser. The technique will open new possibilities in the fabrication of micro-optical components with various optical functions.

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Dynamic Response Behavior of Femtosecond Laser-Annealed Indium Zinc Oxide Thin-Film Transistors

  • Shan, Fei;Kim, Sung-Jin
    • Journal of Electrical Engineering and Technology
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    • v.12 no.6
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    • pp.2353-2358
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    • 2017
  • A femtosecond laser pre-annealing process based on indium zinc oxide (IZO) thin-film transistors (TFTs) is fabricated. We demonstrate a stable pre-annealing process to analyze surface structure change of thin films, and we maintain electrical stability and improve electrical performance. Furthermore, dynamic electrical characteristics of the IZO TFTs were investigated. Femtosecond laser pre-annealing process-based IZO TFTs exhibit a field-effect mobility of $3.75cm^2/Vs$, an $I_{on}/I_{off}$ ratio of $1.77{\times}10^5$, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. And the IZO-based inverter shows a fast switching behavior response. From this study, IZO TFTs from using the femtosecond laser annealing technique were found to strongly affect the electrical performance and charge transport dynamics in electronic devices.

Micromachined Properties of a polyimide by a femtosecond laser (펨토초 레이저에 의한 폴리이마이드 가공 특성)

  • Min, Chul-Ki;Lee, Man-Seop
    • Laser Solutions
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    • v.11 no.2
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    • pp.20-25
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    • 2008
  • Polyimide is one of the useful materials in industry. The surface treatment of polyimide by a femtosecond laser can help accurate and fine fabrication of microstructure. And it can change the transmittance and reflectance of polyimide, too. We put femtosecond laser pulses on polyimide for rectangular or square type surface treaments and observe the change of transmittance and reflectance. Pulsewidth is 172 fs, laser power changes for fabrication are from 5 mW to 20 mW, and transmittance and reflectance are measured under 20m W, 300m W, and 920 mW. Pulse patterning is stable and almost no unwanted surface damage is shown. As power increases, working depth increases but working line width does not increase significantly. As speed changes, they also have same results. It shows the efficiency of a femtosecond laser is good and thermal damage is small for polyimide.

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Femtosecond Laser Lithography for Maskless PR Patterning (펨토초 레이저를 이용한 미세 PR 패터닝)

  • Sohn, Ik-Bu;Ko, Myeong-Jin;Kim, Young Seop;Noh, Young-Chul
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.6
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    • pp.36-40
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    • 2009
  • Development of maskless lithography techniques can provide a potential solution for the photomask cost issue. Furthermore, it could open a market for small scale manufacturing applications. Since femtosecond lasers have been found suitable for processing of a wide range of materials with sub-micrometer resolution, it is attractive to use this technique for maskless lithography. As a femtosecond laser has recently been developed, both of high power and high photon density are easily obtained. The high photon density results in photopolymerization of photoresist whose absorption spectrum is shorter than that of the femtosecond laser. The maskless lithography using the two-photon absorption (TPA) makes micro structures. In this paper, we present a femtosecond laser direct write lithography for submicron PR patterning, which show great potential for future application.

Structural Analysis of a Cavitary Region Created by Femtosecond Laser Process

  • Fujii, Takaaki;Goya, Kenji;Watanabe, Kazuhiro
    • Journal of Power System Engineering
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    • v.19 no.3
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    • pp.5-10
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    • 2015
  • Femtosecond laser machining has been applied for creating a sensor function in silica glass optical fibers. Femtosecond laser pulses make it possible to fabricate micro structures in processed regions of a very thin glass fiber line because femtosecond laser pulses can extremely minimize thermal effects. With the laser machining to optical fiber using a single shot of 210-fs laser at a wavelength of 800 nm, it was observed that a processed region surrounded a thin layer which seemed to be a hollow cavity monitored by scanning electron microscopy (SEM). This study aims at a theoretical investigation for the processed region by using a numerical analysis in order to embed sensing function to optical fibers. Numerical methods based finite element method (FEM) has been used for an optical waveguide modeling. This report suggests two types modeling and describes a comparative study on optical losses obtained by the experiment and the numerical analysis.

High-Speed Femtosecond Laser Micromachining with a Scanner (스캐너를 이용한 고속 펨토초 레이저 가공 기술)

  • Sohn, Ik-Bu;Choi, Sung-Chul;Noh, Young-Chul;Ko, Do-Kyeong;Lee, Jong-Min
    • Laser Solutions
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    • v.9 no.2
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    • pp.11-15
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    • 2006
  • We report experimental results on the high-speed micromachining using a femtosecond laser (800 nm, 130 fs, 1kHz) and galvanometer scanner system (Raylase, Germany). Periodic hole drilling of silicon and glass with the scan speed of 1-20 mm/s is demonstrated. Finally, we demonstrate the utility of the femtosecond laser application to ITO patterning by using a high-speed femtosecond laser scanner system.

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Femtosecond laser induced shock generation and its application (펨토초 레이저 유발 shock 형성 및 그 응용)

  • Jeoung, Sae Chae;Lee, Heung Soon;Sidhu, M.S.;Moon, Heh-Young
    • Laser Solutions
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    • v.17 no.4
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    • pp.1-6
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    • 2014
  • Femtosecond laser induced shock generation in water and vitreous humor of enucleated porcine eyeball was investigated. When focusing the femtosecond laser into the liquid mediums, the acoustic waves with a frequency of about 15.6kHz could be observed by using wide-band microphone. The amplitude of the acoustic signals from water has attained a maximum under a laser power of about 5mW. Further increment of the power results in a decrement of the acoustic signals due to nonlinear optical process including filamentation of laser beam. We have further investigated the effect of femtosecond laser induced acoustic waves by applying the laser pulse into enucleated porcine eyeball. The comparative studies on both healthy and diseased eyeballs led us propose that the femtosecond laser pulses could be utilized as a novel tools for treatment of partially detached retina layers from their choroid structures.

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Femtosecond laser induced photo-expansion of organic thin films

  • Chae, Sang-Min;Lee, Myeong-Su;Choe, Ji-Yeon;Lee, Hyeon-Hwi;Kim, Hyo-Jeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.120.2-120.2
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    • 2015
  • We propose a novel direct writing technique with a femtosecond laser enabling selective modification of not only the morphology of conducting polymer thin films but also the orientation and alignment of the polymer crystal. Surface relief gratings resulting from photoexpansion on P3HT:PCBM and PEDOT:PSS thin films were fabricated by femtosecond laser direct writing. The photoexpansion was induced at laser fluence below the ablation threshold of the thin film. The morphology (size and shape) of photoexpansion could be quantitatively controlled by laser writing parameters such as focused beam size, writing speed, and laser fluence. GIWAX results showed that face-on P3HT crystals were largely increased in the photoexpansion in comparison with pristine region of the thin film. In addition, the face-on P3HTs in the photoexpansion were aligned with their orientation along the polarization of the laser. The micro-RAMAN spectra confirmed that neither chemical composition change nor the polymer chain breaking was observable after femtosecond laser irradiation. We believe that this laser direct writing technique opens a new door to the fabrication of more efficient OPVs via non-contact, toxic-free approach.

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Direct writing of multi-layer diffraction grating inside fused silica glass by using a femtosecond laser (펨토초 레이저를 이용한 실리카 내부의 다층 회절격자 가공 기술)

  • Choi, Hun-Kook;Kim, Jin-Tae;Sohn, Ik-Bu;Noh, Young-Chul
    • Laser Solutions
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    • v.14 no.3
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    • pp.17-20
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    • 2011
  • We fabricated a multi-layer diffraction grating inside fused silica glass by using a femtosecond laser direct writing method. The femtosecond laser with a wavelength of 515 nm, a pulse width of 250 fs, a repetition rate of 100 kHz, and an average output power of 6 W was used. Two layer diffraction grating with a grating period of $6{\mu}m$ was successfully fabricated with the layer gap of 0.5, 1, 2, 3, and $5{\mu}m$, respectively. Also, we investigated the diffraction pattern by illuminating a He-Ne laser beam. Finally, we demonstrated the diffraction grating with a grating period of $3{\mu}m$ by adjusting the gap of each layer with a grating period of $6{\mu}m$. Femtosecond laser direct writing technology of multi-layer has a potential to fabricate the diffraction grating with a grating period of below $1.5{\mu}m$.

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